Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f4f97b3ea90130520afb478cbc2918be2b6587b8
Commit:     f4f97b3ea90130520afb478cbc2918be2b6587b8
Parent:     c85b04c3749507546f6d5868976e4793e35c2ec0
Author:     Jeremy Fitzhardinge <[EMAIL PROTECTED]>
AuthorDate: Tue Jul 17 18:37:05 2007 -0700
Committer:  Jeremy Fitzhardinge <[EMAIL PROTECTED]>
CommitDate: Wed Jul 18 08:47:43 2007 -0700

    xen: Complete pagetable pinning
    
    Xen requires all active pagetables to be marked read-only.  When the
    base of the pagetable is loaded into %cr3, the hypervisor validates
    the entire pagetable and only allows the load to proceed if it all
    checks out.
    
    This is pretty slow, so to mitigate this cost Xen has a notion of
    pinned pagetables.  Pinned pagetables are pagetables which are
    considered to be active even if no processor's cr3 is pointing to is.
    This means that it must remain read-only and all updates are validated
    by the hypervisor.  This makes context switches much cheaper, because
    the hypervisor doesn't need to revalidate the pagetable each time.
    
    This also adds a new paravirt hook which is called during setup once
    the zones and memory allocator have been initialized.  When the
    init_mm pagetable is first built, the struct page array does not yet
    exist, and so there's nowhere to put he init_mm pagetable's PG_pinned
    flags.  Once the zones are initialized and the struct page array
    exists, we can set the PG_pinned flags for those pages.
    
    This patch also adds the Xen support for pte pages allocated out of
    highmem (highpte) by implementing xen_kmap_atomic_pte.
    
    Signed-off-by: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
    Signed-off-by: Chris Wright <[EMAIL PROTECTED]>
    Cc: Zach Amsden <[EMAIL PROTECTED]>
---
 arch/i386/xen/enlighten.c |   87 ++++++++++++---
 arch/i386/xen/mmu.c       |  260 +++++++++++++++++++++++++++++----------------
 arch/i386/xen/mmu.h       |    2 +-
 arch/i386/xen/xen-ops.h   |    2 +
 4 files changed, 242 insertions(+), 109 deletions(-)

diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c
index 25eb359..86e68e6 100644
--- a/arch/i386/xen/enlighten.c
+++ b/arch/i386/xen/enlighten.c
@@ -21,6 +21,9 @@
 #include <linux/sched.h>
 #include <linux/bootmem.h>
 #include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/page-flags.h>
+#include <linux/highmem.h>
 
 #include <xen/interface/xen.h>
 #include <xen/interface/physdev.h>
@@ -500,32 +503,59 @@ static void xen_write_cr3(unsigned long cr3)
        }
 }
 
-static void xen_alloc_pt(struct mm_struct *mm, u32 pfn)
+/* Early in boot, while setting up the initial pagetable, assume
+   everything is pinned. */
+static void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn)
 {
-       /* XXX pfn isn't necessarily a lowmem page */
+       BUG_ON(mem_map);        /* should only be used early */
        make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
 }
 
-static void xen_alloc_pd(u32 pfn)
+/* This needs to make sure the new pte page is pinned iff its being
+   attached to a pinned pagetable. */
+static void xen_alloc_pt(struct mm_struct *mm, u32 pfn)
 {
-       make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
-}
+       struct page *page = pfn_to_page(pfn);
 
-static void xen_release_pd(u32 pfn)
-{
-       make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
+       if (PagePinned(virt_to_page(mm->pgd))) {
+               SetPagePinned(page);
+
+               if (!PageHighMem(page))
+                       make_lowmem_page_readonly(__va(PFN_PHYS(pfn)));
+               else
+                       /* make sure there are no stray mappings of
+                          this page */
+                       kmap_flush_unused();
+       }
 }
 
+/* This should never happen until we're OK to use struct page */
 static void xen_release_pt(u32 pfn)
 {
-       make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
+       struct page *page = pfn_to_page(pfn);
+
+       if (PagePinned(page)) {
+               if (!PageHighMem(page))
+                       make_lowmem_page_readwrite(__va(PFN_PHYS(pfn)));
+       }
 }
 
-static void xen_alloc_pd_clone(u32 pfn, u32 clonepfn,
-                                       u32 start, u32 count)
+#ifdef CONFIG_HIGHPTE
+static void *xen_kmap_atomic_pte(struct page *page, enum km_type type)
 {
-       xen_alloc_pd(pfn);
+       pgprot_t prot = PAGE_KERNEL;
+
+       if (PagePinned(page))
+               prot = PAGE_KERNEL_RO;
+
+       if (0 && PageHighMem(page))
+               printk("mapping highpte %lx type %d prot %s\n",
+                      page_to_pfn(page), type,
+                      (unsigned long)pgprot_val(prot) & _PAGE_RW ? "WRITE" : 
"READ");
+
+       return kmap_atomic_prot(page, type, prot);
 }
+#endif
 
 static __init void xen_pagetable_setup_start(pgd_t *base)
 {
@@ -553,7 +583,7 @@ static __init void xen_pagetable_setup_start(pgd_t *base)
                                memcpy(pmd, (void *)pgd_page_vaddr(xen_pgd[i]),
                                       PAGE_SIZE);
 
-                               xen_alloc_pd(PFN_DOWN(__pa(pmd)));
+                               make_lowmem_page_readonly(pmd);
 
                                set_pgd(&base[i], __pgd(1 + __pa(pmd)));
                        } else
@@ -574,6 +604,10 @@ static __init void xen_pagetable_setup_start(pgd_t *base)
 
 static __init void xen_pagetable_setup_done(pgd_t *base)
 {
+       /* This will work as long as patching hasn't happened yet
+          (which it hasn't) */
+       paravirt_ops.alloc_pt = xen_alloc_pt;
+
        if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                /*
                 * Create a mapping for the shared info page.
@@ -591,7 +625,19 @@ static __init void xen_pagetable_setup_done(pgd_t *base)
                HYPERVISOR_shared_info =
                        (struct shared_info *)__va(xen_start_info->shared_info);
 
-       xen_pgd_pin(base);
+       /* Actually pin the pagetable down, but we can't set PG_pinned
+          yet because the page structures don't exist yet. */
+       {
+               struct mmuext_op op;
+#ifdef CONFIG_X86_PAE
+               op.cmd = MMUEXT_PIN_L3_TABLE;
+#else
+               op.cmd = MMUEXT_PIN_L3_TABLE;
+#endif
+               op.arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(base)));
+               if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF))
+                       BUG();
+       }
 
        xen_vcpu_setup(smp_processor_id());
 }
@@ -608,6 +654,7 @@ static const struct paravirt_ops xen_paravirt_ops 
__initdata = {
        .memory_setup = xen_memory_setup,
        .arch_setup = xen_arch_setup,
        .init_IRQ = xen_init_IRQ,
+       .post_allocator_init = xen_mark_init_mm_pinned,
 
        .time_init = xen_time_init,
        .set_wallclock = xen_set_wallclock,
@@ -688,11 +735,15 @@ static const struct paravirt_ops xen_paravirt_ops 
__initdata = {
        .pagetable_setup_start = xen_pagetable_setup_start,
        .pagetable_setup_done = xen_pagetable_setup_done,
 
-       .alloc_pt = xen_alloc_pt,
-       .alloc_pd = xen_alloc_pd,
-       .alloc_pd_clone = xen_alloc_pd_clone,
-       .release_pd = xen_release_pd,
+       .alloc_pt = xen_alloc_pt_init,
        .release_pt = xen_release_pt,
+       .alloc_pd = paravirt_nop,
+       .alloc_pd_clone = paravirt_nop,
+       .release_pd = paravirt_nop,
+
+#ifdef CONFIG_HIGHPTE
+       .kmap_atomic_pte = xen_kmap_atomic_pte,
+#endif
 
        .set_pte = xen_set_pte,
        .set_pte_at = xen_set_pte_at,
diff --git a/arch/i386/xen/mmu.c b/arch/i386/xen/mmu.c
index de16cb5..53501ce 100644
--- a/arch/i386/xen/mmu.c
+++ b/arch/i386/xen/mmu.c
@@ -38,19 +38,22 @@
  *
  * Jeremy Fitzhardinge <[EMAIL PROTECTED]>, XenSource Inc, 2007
  */
+#include <linux/highmem.h>
 #include <linux/bug.h>
 #include <linux/sched.h>
 
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
+#include <asm/paravirt.h>
 
 #include <asm/xen/hypercall.h>
-#include <asm/paravirt.h>
+#include <asm/xen/hypervisor.h>
 
 #include <xen/page.h>
 #include <xen/interface/xen.h>
 
+#include "multicalls.h"
 #include "mmu.h"
 
 xmaddr_t arbitrary_virt_to_machine(unsigned long address)
@@ -92,16 +95,6 @@ void make_lowmem_page_readwrite(void *vaddr)
 }
 
 
-void xen_set_pte(pte_t *ptep, pte_t pte)
-{
-       struct mmu_update u;
-
-       u.ptr = virt_to_machine(ptep).maddr;
-       u.val = pte_val_ma(pte);
-       if (HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0)
-               BUG();
-}
-
 void xen_set_pmd(pmd_t *ptr, pmd_t val)
 {
        struct mmu_update u;
@@ -112,18 +105,6 @@ void xen_set_pmd(pmd_t *ptr, pmd_t val)
                BUG();
 }
 
-#ifdef CONFIG_X86_PAE
-void xen_set_pud(pud_t *ptr, pud_t val)
-{
-       struct mmu_update u;
-
-       u.ptr = virt_to_machine(ptr).maddr;
-       u.val = pud_val_ma(val);
-       if (HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0)
-               BUG();
-}
-#endif
-
 /*
  * Associate a virtual page frame with a given physical page frame
  * and protection flags for that frame.
@@ -170,6 +151,23 @@ void xen_set_pte_at(struct mm_struct *mm, unsigned long 
addr,
 }
 
 #ifdef CONFIG_X86_PAE
+void xen_set_pud(pud_t *ptr, pud_t val)
+{
+       struct mmu_update u;
+
+       u.ptr = virt_to_machine(ptr).maddr;
+       u.val = pud_val_ma(val);
+       if (HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF) < 0)
+               BUG();
+}
+
+void xen_set_pte(pte_t *ptep, pte_t pte)
+{
+       ptep->pte_high = pte.pte_high;
+       smp_wmb();
+       ptep->pte_low = pte.pte_low;
+}
+
 void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
 {
        set_64bit((u64 *)ptep, pte_val_ma(pte));
@@ -239,6 +237,11 @@ pgd_t xen_make_pgd(unsigned long long pgd)
        return (pgd_t){ pgd };
 }
 #else  /* !PAE */
+void xen_set_pte(pte_t *ptep, pte_t pte)
+{
+       *ptep = pte;
+}
+
 unsigned long xen_pte_val(pte_t pte)
 {
        unsigned long ret = pte.pte_low;
@@ -249,13 +252,6 @@ unsigned long xen_pte_val(pte_t pte)
        return ret;
 }
 
-unsigned long xen_pmd_val(pmd_t pmd)
-{
-       /* a BUG here is a lot easier to track down than a NULL eip */
-       BUG();
-       return 0;
-}
-
 unsigned long xen_pgd_val(pgd_t pgd)
 {
        unsigned long ret = pgd.pgd;
@@ -272,13 +268,6 @@ pte_t xen_make_pte(unsigned long pte)
        return (pte_t){ pte };
 }
 
-pmd_t xen_make_pmd(unsigned long pmd)
-{
-       /* a BUG here is a lot easier to track down than a NULL eip */
-       BUG();
-       return __pmd(0);
-}
-
 pgd_t xen_make_pgd(unsigned long pgd)
 {
        if (pgd & _PAGE_PRESENT)
@@ -290,108 +279,199 @@ pgd_t xen_make_pgd(unsigned long pgd)
 
 
 
-static void pgd_walk_set_prot(void *pt, pgprot_t flags)
-{
-       unsigned long pfn = PFN_DOWN(__pa(pt));
-
-       if (HYPERVISOR_update_va_mapping((unsigned long)pt,
-                                        pfn_pte(pfn, flags), 0) < 0)
-               BUG();
-}
-
-static void pgd_walk(pgd_t *pgd_base, pgprot_t flags)
+/*
+  (Yet another) pagetable walker.  This one is intended for pinning a
+  pagetable.  This means that it walks a pagetable and calls the
+  callback function on each page it finds making up the page table,
+  at every level.  It walks the entire pagetable, but it only bothers
+  pinning pte pages which are below pte_limit.  In the normal case
+  this will be TASK_SIZE, but at boot we need to pin up to
+  FIXADDR_TOP.  But the important bit is that we don't pin beyond
+  there, because then we start getting into Xen's ptes.
+*/
+static int pgd_walk(pgd_t *pgd_base, int (*func)(struct page *, unsigned),
+                   unsigned long limit)
 {
        pgd_t *pgd = pgd_base;
-       pud_t *pud;
-       pmd_t *pmd;
-       pte_t *pte;
-       int    g, u, m;
+       int flush = 0;
+       unsigned long addr = 0;
+       unsigned long pgd_next;
+
+       BUG_ON(limit > FIXADDR_TOP);
 
        if (xen_feature(XENFEAT_auto_translated_physmap))
-               return;
+               return 0;
+
+       for (; addr != FIXADDR_TOP; pgd++, addr = pgd_next) {
+               pud_t *pud;
+               unsigned long pud_limit, pud_next;
 
-       for (g = 0; g < USER_PTRS_PER_PGD; g++, pgd++) {
-               if (pgd_none(*pgd))
+               pgd_next = pud_limit = pgd_addr_end(addr, FIXADDR_TOP);
+
+               if (!pgd_val(*pgd))
                        continue;
+
                pud = pud_offset(pgd, 0);
 
                if (PTRS_PER_PUD > 1) /* not folded */
-                       pgd_walk_set_prot(pud, flags);
+                       flush |= (*func)(virt_to_page(pud), 0);
+
+               for (; addr != pud_limit; pud++, addr = pud_next) {
+                       pmd_t *pmd;
+                       unsigned long pmd_limit;
+
+                       pud_next = pud_addr_end(addr, pud_limit);
+
+                       if (pud_next < limit)
+                               pmd_limit = pud_next;
+                       else
+                               pmd_limit = limit;
 
-               for (u = 0; u < PTRS_PER_PUD; u++, pud++) {
                        if (pud_none(*pud))
                                continue;
+
                        pmd = pmd_offset(pud, 0);
 
                        if (PTRS_PER_PMD > 1) /* not folded */
-                               pgd_walk_set_prot(pmd, flags);
+                               flush |= (*func)(virt_to_page(pmd), 0);
+
+                       for (; addr != pmd_limit; pmd++) {
+                               addr += (PAGE_SIZE * PTRS_PER_PTE);
+                               if ((pmd_limit-1) < (addr-1)) {
+                                       addr = pmd_limit;
+                                       break;
+                               }
 
-                       for (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
                                if (pmd_none(*pmd))
                                        continue;
 
-                               /* This can get called before mem_map
-                                  is set up, so we assume nothing is
-                                  highmem at that point. */
-                               if (mem_map == NULL ||
-                                   !PageHighMem(pmd_page(*pmd))) {
-                                       pte = pte_offset_kernel(pmd, 0);
-                                       pgd_walk_set_prot(pte, flags);
-                               }
+                               flush |= (*func)(pmd_page(*pmd), 0);
                        }
                }
        }
 
-       if (HYPERVISOR_update_va_mapping((unsigned long)pgd_base,
-                                        pfn_pte(PFN_DOWN(__pa(pgd_base)),
-                                                flags),
-                                        UVMF_TLB_FLUSH) < 0)
-               BUG();
+       flush |= (*func)(virt_to_page(pgd_base), UVMF_TLB_FLUSH);
+
+       return flush;
 }
 
+static int pin_page(struct page *page, unsigned flags)
+{
+       unsigned pgfl = test_and_set_bit(PG_pinned, &page->flags);
+       int flush;
+
+       if (pgfl)
+               flush = 0;              /* already pinned */
+       else if (PageHighMem(page))
+               /* kmaps need flushing if we found an unpinned
+                  highpage */
+               flush = 1;
+       else {
+               void *pt = lowmem_page_address(page);
+               unsigned long pfn = page_to_pfn(page);
+               struct multicall_space mcs = __xen_mc_entry(0);
+
+               flush = 0;
+
+               MULTI_update_va_mapping(mcs.mc, (unsigned long)pt,
+                                       pfn_pte(pfn, PAGE_KERNEL_RO),
+                                       flags);
+       }
+
+       return flush;
+}
 
-/* This is called just after a mm has been duplicated from its parent,
-   but it has not been used yet.  We need to make sure that its
-   pagetable is all read-only, and can be pinned. */
+/* This is called just after a mm has been created, but it has not
+   been used yet.  We need to make sure that its pagetable is all
+   read-only, and can be pinned. */
 void xen_pgd_pin(pgd_t *pgd)
 {
-       struct mmuext_op op;
+       struct multicall_space mcs;
+       struct mmuext_op *op;
 
-       pgd_walk(pgd, PAGE_KERNEL_RO);
+       xen_mc_batch();
 
-#if defined(CONFIG_X86_PAE)
-       op.cmd = MMUEXT_PIN_L3_TABLE;
+       if (pgd_walk(pgd, pin_page, TASK_SIZE))
+               kmap_flush_unused();
+
+       mcs = __xen_mc_entry(sizeof(*op));
+       op = mcs.args;
+
+#ifdef CONFIG_X86_PAE
+       op->cmd = MMUEXT_PIN_L3_TABLE;
 #else
-       op.cmd = MMUEXT_PIN_L2_TABLE;
+       op->cmd = MMUEXT_PIN_L2_TABLE;
 #endif
-       op.arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd)));
-       if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0)
-               BUG();
+       op->arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd)));
+       MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
+
+       xen_mc_issue(0);
 }
 
-/* Release a pagetables pages back as normal RW */
-void xen_pgd_unpin(pgd_t *pgd)
+/* The init_mm pagetable is really pinned as soon as its created, but
+   that's before we have page structures to store the bits.  So do all
+   the book-keeping now. */
+static __init int mark_pinned(struct page *page, unsigned flags)
 {
-       struct mmuext_op op;
+       SetPagePinned(page);
+       return 0;
+}
 
-       op.cmd = MMUEXT_UNPIN_TABLE;
-       op.arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd)));
+void __init xen_mark_init_mm_pinned(void)
+{
+       pgd_walk(init_mm.pgd, mark_pinned, FIXADDR_TOP);
+}
 
-       if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0)
-               BUG();
+static int unpin_page(struct page *page, unsigned flags)
+{
+       unsigned pgfl = test_and_clear_bit(PG_pinned, &page->flags);
 
-       pgd_walk(pgd, PAGE_KERNEL);
+       if (pgfl && !PageHighMem(page)) {
+               void *pt = lowmem_page_address(page);
+               unsigned long pfn = page_to_pfn(page);
+               struct multicall_space mcs = __xen_mc_entry(0);
+
+               MULTI_update_va_mapping(mcs.mc, (unsigned long)pt,
+                                       pfn_pte(pfn, PAGE_KERNEL),
+                                       flags);
+       }
+
+       return 0;               /* never need to flush on unpin */
 }
 
+/* Release a pagetables pages back as normal RW */
+static void xen_pgd_unpin(pgd_t *pgd)
+{
+       struct mmuext_op *op;
+       struct multicall_space mcs;
+
+       xen_mc_batch();
+
+       mcs = __xen_mc_entry(sizeof(*op));
+
+       op = mcs.args;
+       op->cmd = MMUEXT_UNPIN_TABLE;
+       op->arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd)));
+
+       MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
+
+       pgd_walk(pgd, unpin_page, TASK_SIZE);
+
+       xen_mc_issue(0);
+}
 
 void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
+       spin_lock(&next->page_table_lock);
        xen_pgd_pin(next->pgd);
+       spin_unlock(&next->page_table_lock);
 }
 
 void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 {
+       spin_lock(&mm->page_table_lock);
        xen_pgd_pin(mm->pgd);
+       spin_unlock(&mm->page_table_lock);
 }
 
 void xen_exit_mmap(struct mm_struct *mm)
diff --git a/arch/i386/xen/mmu.h b/arch/i386/xen/mmu.h
index 764eaaa..49776fe 100644
--- a/arch/i386/xen/mmu.h
+++ b/arch/i386/xen/mmu.h
@@ -15,7 +15,7 @@ void xen_dup_mmap(struct mm_struct *oldmm, struct mm_struct 
*mm);
 void xen_exit_mmap(struct mm_struct *mm);
 
 void xen_pgd_pin(pgd_t *pgd);
-void xen_pgd_unpin(pgd_t *pgd);
+//void xen_pgd_unpin(pgd_t *pgd);
 
 #ifdef CONFIG_X86_PAE
 unsigned long long xen_pte_val(pte_t);
diff --git a/arch/i386/xen/xen-ops.h b/arch/i386/xen/xen-ops.h
index 79648fe..54d98b5 100644
--- a/arch/i386/xen/xen-ops.h
+++ b/arch/i386/xen/xen-ops.h
@@ -20,6 +20,8 @@ unsigned long xen_get_wallclock(void);
 int xen_set_wallclock(unsigned long time);
 cycle_t xen_clocksource_read(void);
 
+void xen_mark_init_mm_pinned(void);
+
 DECLARE_PER_CPU(enum paravirt_lazy_mode, xen_lazy_mode);
 
 static inline unsigned xen_get_lazy_mode(void)
-
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