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KVM: MMU: Consolidate two guest pte reads in kvm_mmu_pte_write() 

kvm_mmu_pte_write() reads guest ptes in two different occasions, both to
allow a 32-bit pae guest to update a pte with 4-byte writes.  Consolidate
these into a single read, which also allows us to consolidate another read
from an invlpg speculating a gpte into the shadow page table.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
hifive-unleashed-5.1
Avi Kivity 2010-03-15 13:59:53 +02:00
parent d57e2c0740
commit 72016f3a42
1 changed files with 31 additions and 38 deletions
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69
arch/x86/kvm/mmu.c
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@ -2560,36 +2560,11 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
}
static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
const u8 *new, int bytes)
u64 gpte)
{
gfn_t gfn;
int r;
u64 gpte = 0;
pfn_t pfn;
if (bytes != 4 && bytes != 8)
return;
/*
* Assume that the pte write on a page table of the same type
* as the current vcpu paging mode. This is nearly always true
* (might be false while changing modes). Note it is verified later
* by update_pte().
*/
if (is_pae(vcpu)) {
/* Handle a 32-bit guest writing two halves of a 64-bit gpte */
if ((bytes == 4) && (gpa % 4 == 0)) {
r = kvm_read_guest(vcpu->kvm, gpa & ~(u64)7, &gpte, 8);
if (r)
return;
memcpy((void *)&gpte + (gpa % 8), new, 4);
} else if ((bytes == 8) && (gpa % 8 == 0)) {
memcpy((void *)&gpte, new, 8);
}
} else {
if ((bytes == 4) && (gpa % 4 == 0))
memcpy((void *)&gpte, new, 4);
}
if (!is_present_gpte(gpte))
return;
gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
@ -2640,7 +2615,34 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
int r;
pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
mmu_guess_page_from_pte_write(vcpu, gpa, new, bytes);
switch (bytes) {
case 4:
gentry = *(const u32 *)new;
break;
case 8:
gentry = *(const u64 *)new;
break;
default:
gentry = 0;
break;
}
/*
* Assume that the pte write on a page table of the same type
* as the current vcpu paging mode. This is nearly always true
* (might be false while changing modes). Note it is verified later
* by update_pte().
*/
if (is_pae(vcpu) && bytes == 4) {
/* Handle a 32-bit guest writing two halves of a 64-bit gpte */
gpa &= ~(gpa_t)7;
r = kvm_read_guest(vcpu->kvm, gpa, &gentry, 8);
if (r)
gentry = 0;
}
mmu_guess_page_from_pte_write(vcpu, gpa, gentry);
spin_lock(&vcpu->kvm->mmu_lock);
kvm_mmu_access_page(vcpu, gfn);
kvm_mmu_free_some_pages(vcpu);
@ -2705,20 +2707,11 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
continue;
}
spte = &sp->spt[page_offset / sizeof(*spte)];
if ((gpa & (pte_size - 1)) || (bytes < pte_size)) {
gentry = 0;
r = kvm_read_guest_atomic(vcpu->kvm,
gpa & ~(u64)(pte_size - 1),
&gentry, pte_size);
new = (const void *)&gentry;
if (r < 0)
new = NULL;
}
while (npte--) {
entry = *spte;
mmu_pte_write_zap_pte(vcpu, sp, spte);
if (new)
mmu_pte_write_new_pte(vcpu, sp, spte, new);
if (gentry)
mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);
mmu_pte_write_flush_tlb(vcpu, entry, *spte);
++spte;
}