zte's code,first commit
Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/drivers/lguest/page_tables.c b/ap/os/linux/linux-3.4.x/drivers/lguest/page_tables.c
new file mode 100644
index 0000000..3b62be1
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/drivers/lguest/page_tables.c
@@ -0,0 +1,1152 @@
+/*P:700
+ * The pagetable code, on the other hand, still shows the scars of
+ * previous encounters. It's functional, and as neat as it can be in the
+ * circumstances, but be wary, for these things are subtle and break easily.
+ * The Guest provides a virtual to physical mapping, but we can neither trust
+ * it nor use it: we verify and convert it here then point the CPU to the
+ * converted Guest pages when running the Guest.
+:*/
+
+/* Copyright (C) Rusty Russell IBM Corporation 2006.
+ * GPL v2 and any later version */
+#include <linux/mm.h>
+#include <linux/gfp.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+#include <linux/percpu.h>
+#include <asm/tlbflush.h>
+#include <asm/uaccess.h>
+#include "lg.h"
+
+/*M:008
+ * We hold reference to pages, which prevents them from being swapped.
+ * It'd be nice to have a callback in the "struct mm_struct" when Linux wants
+ * to swap out. If we had this, and a shrinker callback to trim PTE pages, we
+ * could probably consider launching Guests as non-root.
+:*/
+
+/*H:300
+ * The Page Table Code
+ *
+ * We use two-level page tables for the Guest, or three-level with PAE. If
+ * you're not entirely comfortable with virtual addresses, physical addresses
+ * and page tables then I recommend you review arch/x86/lguest/boot.c's "Page
+ * Table Handling" (with diagrams!).
+ *
+ * The Guest keeps page tables, but we maintain the actual ones here: these are
+ * called "shadow" page tables. Which is a very Guest-centric name: these are
+ * the real page tables the CPU uses, although we keep them up to date to
+ * reflect the Guest's. (See what I mean about weird naming? Since when do
+ * shadows reflect anything?)
+ *
+ * Anyway, this is the most complicated part of the Host code. There are seven
+ * parts to this:
+ * (i) Looking up a page table entry when the Guest faults,
+ * (ii) Making sure the Guest stack is mapped,
+ * (iii) Setting up a page table entry when the Guest tells us one has changed,
+ * (iv) Switching page tables,
+ * (v) Flushing (throwing away) page tables,
+ * (vi) Mapping the Switcher when the Guest is about to run,
+ * (vii) Setting up the page tables initially.
+:*/
+
+/*
+ * The Switcher uses the complete top PTE page. That's 1024 PTE entries (4MB)
+ * or 512 PTE entries with PAE (2MB).
+ */
+#define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1)
+
+/*
+ * For PAE we need the PMD index as well. We use the last 2MB, so we
+ * will need the last pmd entry of the last pmd page.
+ */
+#ifdef CONFIG_X86_PAE
+#define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1)
+#define RESERVE_MEM 2U
+#define CHECK_GPGD_MASK _PAGE_PRESENT
+#else
+#define RESERVE_MEM 4U
+#define CHECK_GPGD_MASK _PAGE_TABLE
+#endif
+
+/*
+ * We actually need a separate PTE page for each CPU. Remember that after the
+ * Switcher code itself comes two pages for each CPU, and we don't want this
+ * CPU's guest to see the pages of any other CPU.
+ */
+static DEFINE_PER_CPU(pte_t *, switcher_pte_pages);
+#define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu)
+
+/*H:320
+ * The page table code is curly enough to need helper functions to keep it
+ * clear and clean. The kernel itself provides many of them; one advantage
+ * of insisting that the Guest and Host use the same CONFIG_PAE setting.
+ *
+ * There are two functions which return pointers to the shadow (aka "real")
+ * page tables.
+ *
+ * spgd_addr() takes the virtual address and returns a pointer to the top-level
+ * page directory entry (PGD) for that address. Since we keep track of several
+ * page tables, the "i" argument tells us which one we're interested in (it's
+ * usually the current one).
+ */
+static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr)
+{
+ unsigned int index = pgd_index(vaddr);
+
+#ifndef CONFIG_X86_PAE
+ /* We kill any Guest trying to touch the Switcher addresses. */
+ if (index >= SWITCHER_PGD_INDEX) {
+ kill_guest(cpu, "attempt to access switcher pages");
+ index = 0;
+ }
+#endif
+ /* Return a pointer index'th pgd entry for the i'th page table. */
+ return &cpu->lg->pgdirs[i].pgdir[index];
+}
+
+#ifdef CONFIG_X86_PAE
+/*
+ * This routine then takes the PGD entry given above, which contains the
+ * address of the PMD page. It then returns a pointer to the PMD entry for the
+ * given address.
+ */
+static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
+{
+ unsigned int index = pmd_index(vaddr);
+ pmd_t *page;
+
+ /* We kill any Guest trying to touch the Switcher addresses. */
+ if (pgd_index(vaddr) == SWITCHER_PGD_INDEX &&
+ index >= SWITCHER_PMD_INDEX) {
+ kill_guest(cpu, "attempt to access switcher pages");
+ index = 0;
+ }
+
+ /* You should never call this if the PGD entry wasn't valid */
+ BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT));
+ page = __va(pgd_pfn(spgd) << PAGE_SHIFT);
+
+ return &page[index];
+}
+#endif
+
+/*
+ * This routine then takes the page directory entry returned above, which
+ * contains the address of the page table entry (PTE) page. It then returns a
+ * pointer to the PTE entry for the given address.
+ */
+static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
+{
+#ifdef CONFIG_X86_PAE
+ pmd_t *pmd = spmd_addr(cpu, spgd, vaddr);
+ pte_t *page = __va(pmd_pfn(*pmd) << PAGE_SHIFT);
+
+ /* You should never call this if the PMD entry wasn't valid */
+ BUG_ON(!(pmd_flags(*pmd) & _PAGE_PRESENT));
+#else
+ pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT);
+ /* You should never call this if the PGD entry wasn't valid */
+ BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT));
+#endif
+
+ return &page[pte_index(vaddr)];
+}
+
+/*
+ * These functions are just like the above, except they access the Guest
+ * page tables. Hence they return a Guest address.
+ */
+static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
+{
+ unsigned int index = vaddr >> (PGDIR_SHIFT);
+ return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t);
+}
+
+#ifdef CONFIG_X86_PAE
+/* Follow the PGD to the PMD. */
+static unsigned long gpmd_addr(pgd_t gpgd, unsigned long vaddr)
+{
+ unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT;
+ BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT));
+ return gpage + pmd_index(vaddr) * sizeof(pmd_t);
+}
+
+/* Follow the PMD to the PTE. */
+static unsigned long gpte_addr(struct lg_cpu *cpu,
+ pmd_t gpmd, unsigned long vaddr)
+{
+ unsigned long gpage = pmd_pfn(gpmd) << PAGE_SHIFT;
+
+ BUG_ON(!(pmd_flags(gpmd) & _PAGE_PRESENT));
+ return gpage + pte_index(vaddr) * sizeof(pte_t);
+}
+#else
+/* Follow the PGD to the PTE (no mid-level for !PAE). */
+static unsigned long gpte_addr(struct lg_cpu *cpu,
+ pgd_t gpgd, unsigned long vaddr)
+{
+ unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT;
+
+ BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT));
+ return gpage + pte_index(vaddr) * sizeof(pte_t);
+}
+#endif
+/*:*/
+
+/*M:007
+ * get_pfn is slow: we could probably try to grab batches of pages here as
+ * an optimization (ie. pre-faulting).
+:*/
+
+/*H:350
+ * This routine takes a page number given by the Guest and converts it to
+ * an actual, physical page number. It can fail for several reasons: the
+ * virtual address might not be mapped by the Launcher, the write flag is set
+ * and the page is read-only, or the write flag was set and the page was
+ * shared so had to be copied, but we ran out of memory.
+ *
+ * This holds a reference to the page, so release_pte() is careful to put that
+ * back.
+ */
+static unsigned long get_pfn(unsigned long virtpfn, int write)
+{
+ struct page *page;
+
+ /* gup me one page at this address please! */
+ if (get_user_pages_fast(virtpfn << PAGE_SHIFT, 1, write, &page) == 1)
+ return page_to_pfn(page);
+
+ /* This value indicates failure. */
+ return -1UL;
+}
+
+/*H:340
+ * Converting a Guest page table entry to a shadow (ie. real) page table
+ * entry can be a little tricky. The flags are (almost) the same, but the
+ * Guest PTE contains a virtual page number: the CPU needs the real page
+ * number.
+ */
+static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write)
+{
+ unsigned long pfn, base, flags;
+
+ /*
+ * The Guest sets the global flag, because it thinks that it is using
+ * PGE. We only told it to use PGE so it would tell us whether it was
+ * flushing a kernel mapping or a userspace mapping. We don't actually
+ * use the global bit, so throw it away.
+ */
+ flags = (pte_flags(gpte) & ~_PAGE_GLOBAL);
+
+ /* The Guest's pages are offset inside the Launcher. */
+ base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE;
+
+ /*
+ * We need a temporary "unsigned long" variable to hold the answer from
+ * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't
+ * fit in spte.pfn. get_pfn() finds the real physical number of the
+ * page, given the virtual number.
+ */
+ pfn = get_pfn(base + pte_pfn(gpte), write);
+ if (pfn == -1UL) {
+ kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte));
+ /*
+ * When we destroy the Guest, we'll go through the shadow page
+ * tables and release_pte() them. Make sure we don't think
+ * this one is valid!
+ */
+ flags = 0;
+ }
+ /* Now we assemble our shadow PTE from the page number and flags. */
+ return pfn_pte(pfn, __pgprot(flags));
+}
+
+/*H:460 And to complete the chain, release_pte() looks like this: */
+static void release_pte(pte_t pte)
+{
+ /*
+ * Remember that get_user_pages_fast() took a reference to the page, in
+ * get_pfn()? We have to put it back now.
+ */
+ if (pte_flags(pte) & _PAGE_PRESENT)
+ put_page(pte_page(pte));
+}
+/*:*/
+
+static void check_gpte(struct lg_cpu *cpu, pte_t gpte)
+{
+ if ((pte_flags(gpte) & _PAGE_PSE) ||
+ pte_pfn(gpte) >= cpu->lg->pfn_limit)
+ kill_guest(cpu, "bad page table entry");
+}
+
+static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd)
+{
+ if ((pgd_flags(gpgd) & ~CHECK_GPGD_MASK) ||
+ (pgd_pfn(gpgd) >= cpu->lg->pfn_limit))
+ kill_guest(cpu, "bad page directory entry");
+}
+
+#ifdef CONFIG_X86_PAE
+static void check_gpmd(struct lg_cpu *cpu, pmd_t gpmd)
+{
+ if ((pmd_flags(gpmd) & ~_PAGE_TABLE) ||
+ (pmd_pfn(gpmd) >= cpu->lg->pfn_limit))
+ kill_guest(cpu, "bad page middle directory entry");
+}
+#endif
+
+/*H:330
+ * (i) Looking up a page table entry when the Guest faults.
+ *
+ * We saw this call in run_guest(): when we see a page fault in the Guest, we
+ * come here. That's because we only set up the shadow page tables lazily as
+ * they're needed, so we get page faults all the time and quietly fix them up
+ * and return to the Guest without it knowing.
+ *
+ * If we fixed up the fault (ie. we mapped the address), this routine returns
+ * true. Otherwise, it was a real fault and we need to tell the Guest.
+ */
+bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
+{
+ pgd_t gpgd;
+ pgd_t *spgd;
+ unsigned long gpte_ptr;
+ pte_t gpte;
+ pte_t *spte;
+
+ /* Mid level for PAE. */
+#ifdef CONFIG_X86_PAE
+ pmd_t *spmd;
+ pmd_t gpmd;
+#endif
+
+ /* First step: get the top-level Guest page table entry. */
+ if (unlikely(cpu->linear_pages)) {
+ /* Faking up a linear mapping. */
+ gpgd = __pgd(CHECK_GPGD_MASK);
+ } else {
+ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
+ /* Toplevel not present? We can't map it in. */
+ if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
+ return false;
+ }
+
+ /* Now look at the matching shadow entry. */
+ spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
+ if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
+ /* No shadow entry: allocate a new shadow PTE page. */
+ unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
+ if (!ptepage) {
+ kill_guest(cpu, "out of memory allocating pte page");
+ return false;
+ }
+ /* We check that the Guest pgd is OK. */
+ check_gpgd(cpu, gpgd);
+ /*
+ * And we copy the flags to the shadow PGD entry. The page
+ * number in the shadow PGD is the page we just allocated.
+ */
+ set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd)));
+ }
+
+#ifdef CONFIG_X86_PAE
+ if (unlikely(cpu->linear_pages)) {
+ /* Faking up a linear mapping. */
+ gpmd = __pmd(_PAGE_TABLE);
+ } else {
+ gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
+ /* Middle level not present? We can't map it in. */
+ if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
+ return false;
+ }
+
+ /* Now look at the matching shadow entry. */
+ spmd = spmd_addr(cpu, *spgd, vaddr);
+
+ if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) {
+ /* No shadow entry: allocate a new shadow PTE page. */
+ unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
+
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
+ if (!ptepage) {
+ kill_guest(cpu, "out of memory allocating pte page");
+ return false;
+ }
+
+ /* We check that the Guest pmd is OK. */
+ check_gpmd(cpu, gpmd);
+
+ /*
+ * And we copy the flags to the shadow PMD entry. The page
+ * number in the shadow PMD is the page we just allocated.
+ */
+ set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd)));
+ }
+
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
+ gpte_ptr = gpte_addr(cpu, gpmd, vaddr);
+#else
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
+ gpte_ptr = gpte_addr(cpu, gpgd, vaddr);
+#endif
+
+ if (unlikely(cpu->linear_pages)) {
+ /* Linear? Make up a PTE which points to same page. */
+ gpte = __pte((vaddr & PAGE_MASK) | _PAGE_RW | _PAGE_PRESENT);
+ } else {
+ /* Read the actual PTE value. */
+ gpte = lgread(cpu, gpte_ptr, pte_t);
+ }
+
+ /* If this page isn't in the Guest page tables, we can't page it in. */
+ if (!(pte_flags(gpte) & _PAGE_PRESENT))
+ return false;
+
+ /*
+ * Check they're not trying to write to a page the Guest wants
+ * read-only (bit 2 of errcode == write).
+ */
+ if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW))
+ return false;
+
+ /* User access to a kernel-only page? (bit 3 == user access) */
+ if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))
+ return false;
+
+ /*
+ * Check that the Guest PTE flags are OK, and the page number is below
+ * the pfn_limit (ie. not mapping the Launcher binary).
+ */
+ check_gpte(cpu, gpte);
+
+ /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */
+ gpte = pte_mkyoung(gpte);
+ if (errcode & 2)
+ gpte = pte_mkdirty(gpte);
+
+ /* Get the pointer to the shadow PTE entry we're going to set. */
+ spte = spte_addr(cpu, *spgd, vaddr);
+
+ /*
+ * If there was a valid shadow PTE entry here before, we release it.
+ * This can happen with a write to a previously read-only entry.
+ */
+ release_pte(*spte);
+
+ /*
+ * If this is a write, we insist that the Guest page is writable (the
+ * final arg to gpte_to_spte()).
+ */
+ if (pte_dirty(gpte))
+ *spte = gpte_to_spte(cpu, gpte, 1);
+ else
+ /*
+ * If this is a read, don't set the "writable" bit in the page
+ * table entry, even if the Guest says it's writable. That way
+ * we will come back here when a write does actually occur, so
+ * we can update the Guest's _PAGE_DIRTY flag.
+ */
+ set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0));
+
+ /*
+ * Finally, we write the Guest PTE entry back: we've set the
+ * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags.
+ */
+ if (likely(!cpu->linear_pages))
+ lgwrite(cpu, gpte_ptr, pte_t, gpte);
+
+ /*
+ * The fault is fixed, the page table is populated, the mapping
+ * manipulated, the result returned and the code complete. A small
+ * delay and a trace of alliteration are the only indications the Guest
+ * has that a page fault occurred at all.
+ */
+ return true;
+}
+
+/*H:360
+ * (ii) Making sure the Guest stack is mapped.
+ *
+ * Remember that direct traps into the Guest need a mapped Guest kernel stack.
+ * pin_stack_pages() calls us here: we could simply call demand_page(), but as
+ * we've seen that logic is quite long, and usually the stack pages are already
+ * mapped, so it's overkill.
+ *
+ * This is a quick version which answers the question: is this virtual address
+ * mapped by the shadow page tables, and is it writable?
+ */
+static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
+{
+ pgd_t *spgd;
+ unsigned long flags;
+
+#ifdef CONFIG_X86_PAE
+ pmd_t *spmd;
+#endif
+ /* Look at the current top level entry: is it present? */
+ spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
+ if (!(pgd_flags(*spgd) & _PAGE_PRESENT))
+ return false;
+
+#ifdef CONFIG_X86_PAE
+ spmd = spmd_addr(cpu, *spgd, vaddr);
+ if (!(pmd_flags(*spmd) & _PAGE_PRESENT))
+ return false;
+#endif
+
+ /*
+ * Check the flags on the pte entry itself: it must be present and
+ * writable.
+ */
+ flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr)));
+
+ return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
+}
+
+/*
+ * So, when pin_stack_pages() asks us to pin a page, we check if it's already
+ * in the page tables, and if not, we call demand_page() with error code 2
+ * (meaning "write").
+ */
+void pin_page(struct lg_cpu *cpu, unsigned long vaddr)
+{
+ if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))
+ kill_guest(cpu, "bad stack page %#lx", vaddr);
+}
+/*:*/
+
+#ifdef CONFIG_X86_PAE
+static void release_pmd(pmd_t *spmd)
+{
+ /* If the entry's not present, there's nothing to release. */
+ if (pmd_flags(*spmd) & _PAGE_PRESENT) {
+ unsigned int i;
+ pte_t *ptepage = __va(pmd_pfn(*spmd) << PAGE_SHIFT);
+ /* For each entry in the page, we might need to release it. */
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ release_pte(ptepage[i]);
+ /* Now we can free the page of PTEs */
+ free_page((long)ptepage);
+ /* And zero out the PMD entry so we never release it twice. */
+ set_pmd(spmd, __pmd(0));
+ }
+}
+
+static void release_pgd(pgd_t *spgd)
+{
+ /* If the entry's not present, there's nothing to release. */
+ if (pgd_flags(*spgd) & _PAGE_PRESENT) {
+ unsigned int i;
+ pmd_t *pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
+
+ for (i = 0; i < PTRS_PER_PMD; i++)
+ release_pmd(&pmdpage[i]);
+
+ /* Now we can free the page of PMDs */
+ free_page((long)pmdpage);
+ /* And zero out the PGD entry so we never release it twice. */
+ set_pgd(spgd, __pgd(0));
+ }
+}
+
+#else /* !CONFIG_X86_PAE */
+/*H:450
+ * If we chase down the release_pgd() code, the non-PAE version looks like
+ * this. The PAE version is almost identical, but instead of calling
+ * release_pte it calls release_pmd(), which looks much like this.
+ */
+static void release_pgd(pgd_t *spgd)
+{
+ /* If the entry's not present, there's nothing to release. */
+ if (pgd_flags(*spgd) & _PAGE_PRESENT) {
+ unsigned int i;
+ /*
+ * Converting the pfn to find the actual PTE page is easy: turn
+ * the page number into a physical address, then convert to a
+ * virtual address (easy for kernel pages like this one).
+ */
+ pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
+ /* For each entry in the page, we might need to release it. */
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ release_pte(ptepage[i]);
+ /* Now we can free the page of PTEs */
+ free_page((long)ptepage);
+ /* And zero out the PGD entry so we never release it twice. */
+ *spgd = __pgd(0);
+ }
+}
+#endif
+
+/*H:445
+ * We saw flush_user_mappings() twice: once from the flush_user_mappings()
+ * hypercall and once in new_pgdir() when we re-used a top-level pgdir page.
+ * It simply releases every PTE page from 0 up to the Guest's kernel address.
+ */
+static void flush_user_mappings(struct lguest *lg, int idx)
+{
+ unsigned int i;
+ /* Release every pgd entry up to the kernel's address. */
+ for (i = 0; i < pgd_index(lg->kernel_address); i++)
+ release_pgd(lg->pgdirs[idx].pgdir + i);
+}
+
+/*H:440
+ * (v) Flushing (throwing away) page tables,
+ *
+ * The Guest has a hypercall to throw away the page tables: it's used when a
+ * large number of mappings have been changed.
+ */
+void guest_pagetable_flush_user(struct lg_cpu *cpu)
+{
+ /* Drop the userspace part of the current page table. */
+ flush_user_mappings(cpu->lg, cpu->cpu_pgd);
+}
+/*:*/
+
+/* We walk down the guest page tables to get a guest-physical address */
+unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
+{
+ pgd_t gpgd;
+ pte_t gpte;
+#ifdef CONFIG_X86_PAE
+ pmd_t gpmd;
+#endif
+
+ /* Still not set up? Just map 1:1. */
+ if (unlikely(cpu->linear_pages))
+ return vaddr;
+
+ /* First step: get the top-level Guest page table entry. */
+ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
+ /* Toplevel not present? We can't map it in. */
+ if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) {
+ kill_guest(cpu, "Bad address %#lx", vaddr);
+ return -1UL;
+ }
+
+#ifdef CONFIG_X86_PAE
+ gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
+ if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
+ kill_guest(cpu, "Bad address %#lx", vaddr);
+ gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t);
+#else
+ gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);
+#endif
+ if (!(pte_flags(gpte) & _PAGE_PRESENT))
+ kill_guest(cpu, "Bad address %#lx", vaddr);
+
+ return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
+}
+
+/*
+ * We keep several page tables. This is a simple routine to find the page
+ * table (if any) corresponding to this top-level address the Guest has given
+ * us.
+ */
+static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
+{
+ unsigned int i;
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ if (lg->pgdirs[i].pgdir && lg->pgdirs[i].gpgdir == pgtable)
+ break;
+ return i;
+}
+
+/*H:435
+ * And this is us, creating the new page directory. If we really do
+ * allocate a new one (and so the kernel parts are not there), we set
+ * blank_pgdir.
+ */
+static unsigned int new_pgdir(struct lg_cpu *cpu,
+ unsigned long gpgdir,
+ int *blank_pgdir)
+{
+ unsigned int next;
+#ifdef CONFIG_X86_PAE
+ pmd_t *pmd_table;
+#endif
+
+ /*
+ * We pick one entry at random to throw out. Choosing the Least
+ * Recently Used might be better, but this is easy.
+ */
+ next = random32() % ARRAY_SIZE(cpu->lg->pgdirs);
+ /* If it's never been allocated at all before, try now. */
+ if (!cpu->lg->pgdirs[next].pgdir) {
+ cpu->lg->pgdirs[next].pgdir =
+ (pgd_t *)get_zeroed_page(GFP_KERNEL);
+ /* If the allocation fails, just keep using the one we have */
+ if (!cpu->lg->pgdirs[next].pgdir)
+ next = cpu->cpu_pgd;
+ else {
+#ifdef CONFIG_X86_PAE
+ /*
+ * In PAE mode, allocate a pmd page and populate the
+ * last pgd entry.
+ */
+ pmd_table = (pmd_t *)get_zeroed_page(GFP_KERNEL);
+ if (!pmd_table) {
+ free_page((long)cpu->lg->pgdirs[next].pgdir);
+ set_pgd(cpu->lg->pgdirs[next].pgdir, __pgd(0));
+ next = cpu->cpu_pgd;
+ } else {
+ set_pgd(cpu->lg->pgdirs[next].pgdir +
+ SWITCHER_PGD_INDEX,
+ __pgd(__pa(pmd_table) | _PAGE_PRESENT));
+ /*
+ * This is a blank page, so there are no kernel
+ * mappings: caller must map the stack!
+ */
+ *blank_pgdir = 1;
+ }
+#else
+ *blank_pgdir = 1;
+#endif
+ }
+ }
+ /* Record which Guest toplevel this shadows. */
+ cpu->lg->pgdirs[next].gpgdir = gpgdir;
+ /* Release all the non-kernel mappings. */
+ flush_user_mappings(cpu->lg, next);
+
+ return next;
+}
+
+/*H:470
+ * Finally, a routine which throws away everything: all PGD entries in all
+ * the shadow page tables, including the Guest's kernel mappings. This is used
+ * when we destroy the Guest.
+ */
+static void release_all_pagetables(struct lguest *lg)
+{
+ unsigned int i, j;
+
+ /* Every shadow pagetable this Guest has */
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ if (lg->pgdirs[i].pgdir) {
+#ifdef CONFIG_X86_PAE
+ pgd_t *spgd;
+ pmd_t *pmdpage;
+ unsigned int k;
+
+ /* Get the last pmd page. */
+ spgd = lg->pgdirs[i].pgdir + SWITCHER_PGD_INDEX;
+ pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
+
+ /*
+ * And release the pmd entries of that pmd page,
+ * except for the switcher pmd.
+ */
+ for (k = 0; k < SWITCHER_PMD_INDEX; k++)
+ release_pmd(&pmdpage[k]);
+#endif
+ /* Every PGD entry except the Switcher at the top */
+ for (j = 0; j < SWITCHER_PGD_INDEX; j++)
+ release_pgd(lg->pgdirs[i].pgdir + j);
+ }
+}
+
+/*
+ * We also throw away everything when a Guest tells us it's changed a kernel
+ * mapping. Since kernel mappings are in every page table, it's easiest to
+ * throw them all away. This traps the Guest in amber for a while as
+ * everything faults back in, but it's rare.
+ */
+void guest_pagetable_clear_all(struct lg_cpu *cpu)
+{
+ release_all_pagetables(cpu->lg);
+ /* We need the Guest kernel stack mapped again. */
+ pin_stack_pages(cpu);
+}
+
+/*H:430
+ * (iv) Switching page tables
+ *
+ * Now we've seen all the page table setting and manipulation, let's see
+ * what happens when the Guest changes page tables (ie. changes the top-level
+ * pgdir). This occurs on almost every context switch.
+ */
+void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
+{
+ int newpgdir, repin = 0;
+
+ /*
+ * The very first time they call this, we're actually running without
+ * any page tables; we've been making it up. Throw them away now.
+ */
+ if (unlikely(cpu->linear_pages)) {
+ release_all_pagetables(cpu->lg);
+ cpu->linear_pages = false;
+ /* Force allocation of a new pgdir. */
+ newpgdir = ARRAY_SIZE(cpu->lg->pgdirs);
+ } else {
+ /* Look to see if we have this one already. */
+ newpgdir = find_pgdir(cpu->lg, pgtable);
+ }
+
+ /*
+ * If not, we allocate or mug an existing one: if it's a fresh one,
+ * repin gets set to 1.
+ */
+ if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs))
+ newpgdir = new_pgdir(cpu, pgtable, &repin);
+ /* Change the current pgd index to the new one. */
+ cpu->cpu_pgd = newpgdir;
+ /* If it was completely blank, we map in the Guest kernel stack */
+ if (repin)
+ pin_stack_pages(cpu);
+}
+/*:*/
+
+/*M:009
+ * Since we throw away all mappings when a kernel mapping changes, our
+ * performance sucks for guests using highmem. In fact, a guest with
+ * PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is
+ * usually slower than a Guest with less memory.
+ *
+ * This, of course, cannot be fixed. It would take some kind of... well, I
+ * don't know, but the term "puissant code-fu" comes to mind.
+:*/
+
+/*H:420
+ * This is the routine which actually sets the page table entry for then
+ * "idx"'th shadow page table.
+ *
+ * Normally, we can just throw out the old entry and replace it with 0: if they
+ * use it demand_page() will put the new entry in. We need to do this anyway:
+ * The Guest expects _PAGE_ACCESSED to be set on its PTE the first time a page
+ * is read from, and _PAGE_DIRTY when it's written to.
+ *
+ * But Avi Kivity pointed out that most Operating Systems (Linux included) set
+ * these bits on PTEs immediately anyway. This is done to save the CPU from
+ * having to update them, but it helps us the same way: if they set
+ * _PAGE_ACCESSED then we can put a read-only PTE entry in immediately, and if
+ * they set _PAGE_DIRTY then we can put a writable PTE entry in immediately.
+ */
+static void do_set_pte(struct lg_cpu *cpu, int idx,
+ unsigned long vaddr, pte_t gpte)
+{
+ /* Look up the matching shadow page directory entry. */
+ pgd_t *spgd = spgd_addr(cpu, idx, vaddr);
+#ifdef CONFIG_X86_PAE
+ pmd_t *spmd;
+#endif
+
+ /* If the top level isn't present, there's no entry to update. */
+ if (pgd_flags(*spgd) & _PAGE_PRESENT) {
+#ifdef CONFIG_X86_PAE
+ spmd = spmd_addr(cpu, *spgd, vaddr);
+ if (pmd_flags(*spmd) & _PAGE_PRESENT) {
+#endif
+ /* Otherwise, start by releasing the existing entry. */
+ pte_t *spte = spte_addr(cpu, *spgd, vaddr);
+ release_pte(*spte);
+
+ /*
+ * If they're setting this entry as dirty or accessed,
+ * we might as well put that entry they've given us in
+ * now. This shaves 10% off a copy-on-write
+ * micro-benchmark.
+ */
+ if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
+ check_gpte(cpu, gpte);
+ set_pte(spte,
+ gpte_to_spte(cpu, gpte,
+ pte_flags(gpte) & _PAGE_DIRTY));
+ } else {
+ /*
+ * Otherwise kill it and we can demand_page()
+ * it in later.
+ */
+ set_pte(spte, __pte(0));
+ }
+#ifdef CONFIG_X86_PAE
+ }
+#endif
+ }
+}
+
+/*H:410
+ * Updating a PTE entry is a little trickier.
+ *
+ * We keep track of several different page tables (the Guest uses one for each
+ * process, so it makes sense to cache at least a few). Each of these have
+ * identical kernel parts: ie. every mapping above PAGE_OFFSET is the same for
+ * all processes. So when the page table above that address changes, we update
+ * all the page tables, not just the current one. This is rare.
+ *
+ * The benefit is that when we have to track a new page table, we can keep all
+ * the kernel mappings. This speeds up context switch immensely.
+ */
+void guest_set_pte(struct lg_cpu *cpu,
+ unsigned long gpgdir, unsigned long vaddr, pte_t gpte)
+{
+ /*
+ * Kernel mappings must be changed on all top levels. Slow, but doesn't
+ * happen often.
+ */
+ if (vaddr >= cpu->lg->kernel_address) {
+ unsigned int i;
+ for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++)
+ if (cpu->lg->pgdirs[i].pgdir)
+ do_set_pte(cpu, i, vaddr, gpte);
+ } else {
+ /* Is this page table one we have a shadow for? */
+ int pgdir = find_pgdir(cpu->lg, gpgdir);
+ if (pgdir != ARRAY_SIZE(cpu->lg->pgdirs))
+ /* If so, do the update. */
+ do_set_pte(cpu, pgdir, vaddr, gpte);
+ }
+}
+
+/*H:400
+ * (iii) Setting up a page table entry when the Guest tells us one has changed.
+ *
+ * Just like we did in interrupts_and_traps.c, it makes sense for us to deal
+ * with the other side of page tables while we're here: what happens when the
+ * Guest asks for a page table to be updated?
+ *
+ * We already saw that demand_page() will fill in the shadow page tables when
+ * needed, so we can simply remove shadow page table entries whenever the Guest
+ * tells us they've changed. When the Guest tries to use the new entry it will
+ * fault and demand_page() will fix it up.
+ *
+ * So with that in mind here's our code to update a (top-level) PGD entry:
+ */
+void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 idx)
+{
+ int pgdir;
+
+ if (idx >= SWITCHER_PGD_INDEX)
+ return;
+
+ /* If they're talking about a page table we have a shadow for... */
+ pgdir = find_pgdir(lg, gpgdir);
+ if (pgdir < ARRAY_SIZE(lg->pgdirs))
+ /* ... throw it away. */
+ release_pgd(lg->pgdirs[pgdir].pgdir + idx);
+}
+
+#ifdef CONFIG_X86_PAE
+/* For setting a mid-level, we just throw everything away. It's easy. */
+void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx)
+{
+ guest_pagetable_clear_all(&lg->cpus[0]);
+}
+#endif
+
+/*H:500
+ * (vii) Setting up the page tables initially.
+ *
+ * When a Guest is first created, set initialize a shadow page table which
+ * we will populate on future faults. The Guest doesn't have any actual
+ * pagetables yet, so we set linear_pages to tell demand_page() to fake it
+ * for the moment.
+ */
+int init_guest_pagetable(struct lguest *lg)
+{
+ struct lg_cpu *cpu = &lg->cpus[0];
+ int allocated = 0;
+
+ /* lg (and lg->cpus[]) starts zeroed: this allocates a new pgdir */
+ cpu->cpu_pgd = new_pgdir(cpu, 0, &allocated);
+ if (!allocated)
+ return -ENOMEM;
+
+ /* We start with a linear mapping until the initialize. */
+ cpu->linear_pages = true;
+ return 0;
+}
+
+/*H:508 When the Guest calls LHCALL_LGUEST_INIT we do more setup. */
+void page_table_guest_data_init(struct lg_cpu *cpu)
+{
+ /* We get the kernel address: above this is all kernel memory. */
+ if (get_user(cpu->lg->kernel_address,
+ &cpu->lg->lguest_data->kernel_address)
+ /*
+ * We tell the Guest that it can't use the top 2 or 4 MB
+ * of virtual addresses used by the Switcher.
+ */
+ || put_user(RESERVE_MEM * 1024 * 1024,
+ &cpu->lg->lguest_data->reserve_mem)) {
+ kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
+ return;
+ }
+
+ /*
+ * In flush_user_mappings() we loop from 0 to
+ * "pgd_index(lg->kernel_address)". This assumes it won't hit the
+ * Switcher mappings, so check that now.
+ */
+#ifdef CONFIG_X86_PAE
+ if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX &&
+ pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX)
+#else
+ if (pgd_index(cpu->lg->kernel_address) >= SWITCHER_PGD_INDEX)
+#endif
+ kill_guest(cpu, "bad kernel address %#lx",
+ cpu->lg->kernel_address);
+}
+
+/* When a Guest dies, our cleanup is fairly simple. */
+void free_guest_pagetable(struct lguest *lg)
+{
+ unsigned int i;
+
+ /* Throw away all page table pages. */
+ release_all_pagetables(lg);
+ /* Now free the top levels: free_page() can handle 0 just fine. */
+ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++)
+ free_page((long)lg->pgdirs[i].pgdir);
+}
+
+/*H:480
+ * (vi) Mapping the Switcher when the Guest is about to run.
+ *
+ * The Switcher and the two pages for this CPU need to be visible in the
+ * Guest (and not the pages for other CPUs). We have the appropriate PTE pages
+ * for each CPU already set up, we just need to hook them in now we know which
+ * Guest is about to run on this CPU.
+ */
+void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
+{
+ pte_t *switcher_pte_page = __this_cpu_read(switcher_pte_pages);
+ pte_t regs_pte;
+
+#ifdef CONFIG_X86_PAE
+ pmd_t switcher_pmd;
+ pmd_t *pmd_table;
+
+ switcher_pmd = pfn_pmd(__pa(switcher_pte_page) >> PAGE_SHIFT,
+ PAGE_KERNEL_EXEC);
+
+ /* Figure out where the pmd page is, by reading the PGD, and converting
+ * it to a virtual address. */
+ pmd_table = __va(pgd_pfn(cpu->lg->
+ pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX])
+ << PAGE_SHIFT);
+ /* Now write it into the shadow page table. */
+ set_pmd(&pmd_table[SWITCHER_PMD_INDEX], switcher_pmd);
+#else
+ pgd_t switcher_pgd;
+
+ /*
+ * Make the last PGD entry for this Guest point to the Switcher's PTE
+ * page for this CPU (with appropriate flags).
+ */
+ switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC);
+
+ cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
+
+#endif
+ /*
+ * We also change the Switcher PTE page. When we're running the Guest,
+ * we want the Guest's "regs" page to appear where the first Switcher
+ * page for this CPU is. This is an optimization: when the Switcher
+ * saves the Guest registers, it saves them into the first page of this
+ * CPU's "struct lguest_pages": if we make sure the Guest's register
+ * page is already mapped there, we don't have to copy them out
+ * again.
+ */
+ regs_pte = pfn_pte(__pa(cpu->regs_page) >> PAGE_SHIFT, PAGE_KERNEL);
+ set_pte(&switcher_pte_page[pte_index((unsigned long)pages)], regs_pte);
+}
+/*:*/
+
+static void free_switcher_pte_pages(void)
+{
+ unsigned int i;
+
+ for_each_possible_cpu(i)
+ free_page((long)switcher_pte_page(i));
+}
+
+/*H:520
+ * Setting up the Switcher PTE page for given CPU is fairly easy, given
+ * the CPU number and the "struct page"s for the Switcher code itself.
+ *
+ * Currently the Switcher is less than a page long, so "pages" is always 1.
+ */
+static __init void populate_switcher_pte_page(unsigned int cpu,
+ struct page *switcher_page[],
+ unsigned int pages)
+{
+ unsigned int i;
+ pte_t *pte = switcher_pte_page(cpu);
+
+ /* The first entries are easy: they map the Switcher code. */
+ for (i = 0; i < pages; i++) {
+ set_pte(&pte[i], mk_pte(switcher_page[i],
+ __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)));
+ }
+
+ /* The only other thing we map is this CPU's pair of pages. */
+ i = pages + cpu*2;
+
+ /* First page (Guest registers) is writable from the Guest */
+ set_pte(&pte[i], pfn_pte(page_to_pfn(switcher_page[i]),
+ __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)));
+
+ /*
+ * The second page contains the "struct lguest_ro_state", and is
+ * read-only.
+ */
+ set_pte(&pte[i+1], pfn_pte(page_to_pfn(switcher_page[i+1]),
+ __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)));
+}
+
+/*
+ * We've made it through the page table code. Perhaps our tired brains are
+ * still processing the details, or perhaps we're simply glad it's over.
+ *
+ * If nothing else, note that all this complexity in juggling shadow page tables
+ * in sync with the Guest's page tables is for one reason: for most Guests this
+ * page table dance determines how bad performance will be. This is why Xen
+ * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD
+ * have implemented shadow page table support directly into hardware.
+ *
+ * There is just one file remaining in the Host.
+ */
+
+/*H:510
+ * At boot or module load time, init_pagetables() allocates and populates
+ * the Switcher PTE page for each CPU.
+ */
+__init int init_pagetables(struct page **switcher_page, unsigned int pages)
+{
+ unsigned int i;
+
+ for_each_possible_cpu(i) {
+ switcher_pte_page(i) = (pte_t *)get_zeroed_page(GFP_KERNEL);
+ if (!switcher_pte_page(i)) {
+ free_switcher_pte_pages();
+ return -ENOMEM;
+ }
+ populate_switcher_pte_page(i, switcher_page, pages);
+ }
+ return 0;
+}
+/*:*/
+
+/* Cleaning up simply involves freeing the PTE page for each CPU. */
+void free_pagetables(void)
+{
+ free_switcher_pte_pages();
+}