Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=79539cec0c3c38d35a1e3e5310d2c562ae6e82b8
Commit: 79539cec0c3c38d35a1e3e5310d2c562ae6e82b8
Parent: 0f74a24c59b814c1c8085251cbea48d339f0c7c6
Author: Avi Kivity <[EMAIL PROTECTED]>
AuthorDate: Wed Nov 21 02:06:21 2007 +0200
Committer: Avi Kivity <[EMAIL PROTECTED]>
CommitDate: Wed Jan 30 17:53:10 2008 +0200
KVM: MMU: Avoid unnecessary remote tlb flushes when guest updates a pte
If all we're doing is increasing permissions on a pte (typical for demand
paging), then there's not need to flush remote tlbs. Worst case they'll
get a spurious page fault.
Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
---
drivers/kvm/mmu.c | 27 ++++++++++++++++++++++++++-
1 files changed, 26 insertions(+), 1 deletions(-)
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 101cd53..281dd5f 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -134,6 +134,8 @@ static int dbg = 1;
#define PT32_DIR_BASE_ADDR_MASK \
(PAGE_MASK & ~((1ULL << (PAGE_SHIFT + PT32_LEVEL_BITS)) - 1))
+#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
+ | PT64_NX_MASK)
#define PFERR_PRESENT_MASK (1U << 0)
#define PFERR_WRITE_MASK (1U << 1)
@@ -1227,7 +1229,6 @@ static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
}
}
set_shadow_pte(spte, shadow_trap_nonpresent_pte);
- kvm_flush_remote_tlbs(vcpu->kvm);
}
static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
@@ -1250,6 +1251,27 @@ static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
offset_in_pte);
}
+static bool need_remote_flush(u64 old, u64 new)
+{
+ if (!is_shadow_present_pte(old))
+ return false;
+ if (!is_shadow_present_pte(new))
+ return true;
+ if ((old ^ new) & PT64_BASE_ADDR_MASK)
+ return true;
+ old ^= PT64_NX_MASK;
+ new ^= PT64_NX_MASK;
+ return (old & ~new & PT64_PERM_MASK) != 0;
+}
+
+static void mmu_pte_write_flush_tlb(struct kvm_vcpu *vcpu, u64 old, u64 new)
+{
+ if (need_remote_flush(old, new))
+ kvm_flush_remote_tlbs(vcpu->kvm);
+ else
+ kvm_mmu_flush_tlb(vcpu);
+}
+
static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
{
u64 *spte = vcpu->last_pte_updated;
@@ -1265,6 +1287,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
struct hlist_node *node, *n;
struct hlist_head *bucket;
unsigned index;
+ u64 entry;
u64 *spte;
unsigned offset = offset_in_page(gpa);
unsigned pte_size;
@@ -1335,9 +1358,11 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
}
spte = &page->spt[page_offset / sizeof(*spte)];
while (npte--) {
+ entry = *spte;
mmu_pte_write_zap_pte(vcpu, page, spte);
mmu_pte_write_new_pte(vcpu, page, spte, new, bytes,
page_offset & (pte_size - 1));
+ mmu_pte_write_flush_tlb(vcpu, entry, *spte);
++spte;
}
}
-
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