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 <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Zach Amsden <zach@vmware.com>
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 <jeremy@xensource.com>, 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 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 @@
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 @@
}
#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 @@
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 @@
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 @@
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 @@
-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 (g = 0; g < USER_PTRS_PER_PGD; g++, pgd++) {
- if (pgd_none(*pgd))
+ for (; addr != FIXADDR_TOP; pgd++, addr = pgd_next) {
+ pud_t *pud;
+ unsigned long pud_limit, pud_next;
+
+ 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 (u = 0; u < PTRS_PER_PUD; u++, pud++) {
+ 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;
+
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 (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
+ for (; addr != pmd_limit; pmd++) {
+ addr += (PAGE_SIZE * PTRS_PER_PTE);
+ if ((pmd_limit-1) < (addr-1)) {
+ addr = pmd_limit;
+ break;
+ }
+
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;
-/* 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. */
+ 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 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);
+}
+
+/* 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)
+{
+ SetPagePinned(page);
+ return 0;
+}
+
+void __init xen_mark_init_mm_pinned(void)
+{
+ pgd_walk(init_mm.pgd, mark_pinned, FIXADDR_TOP);
+}
+
+static int unpin_page(struct page *page, unsigned flags)
+{
+ unsigned pgfl = test_and_clear_bit(PG_pinned, &page->flags);
+
+ 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 */
-void xen_pgd_unpin(pgd_t *pgd)
+static void xen_pgd_unpin(pgd_t *pgd)
{
- struct mmuext_op op;
+ struct mmuext_op *op;
+ struct multicall_space mcs;
- op.cmd = MMUEXT_UNPIN_TABLE;
- op.arg1.mfn = pfn_to_mfn(PFN_DOWN(__pa(pgd)));
+ xen_mc_batch();
- if (HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0)
- BUG();
+ mcs = __xen_mc_entry(sizeof(*op));
- pgd_walk(pgd, PAGE_KERNEL);
+ 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)