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KVM: load_pdptrs() cleanups

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load_pdptrs can be handed an invalid cr3, and it should not oops.
This can happen because we injected #gp in set_cr3() after we set
vcpu->cr3 to the invalid value, or from kvm_vcpu_ioctl_set_sregs(), or
memory configuration changes after the guest did set_cr3().

We should also copy the pdpte array once, before checking and
assigning, otherwise an SMP guest can potentially alter the values
between the check and the set.

Finally one nitpick: ret = 1 should be done as late as possible: this
allows GCC to check for unset "ret" should the function change in
future.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Rusty Russell 2007-07-25 13:29:51 +10:00 committed by Avi Kivity
parent 3ccb8827fb
commit c820c2aa27
1 changed files with 13 additions and 11 deletions
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24
drivers/kvm/kvm_main.c
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@ -442,30 +442,32 @@ static int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
gfn_t pdpt_gfn = cr3 >> PAGE_SHIFT;
unsigned offset = ((cr3 & (PAGE_SIZE-1)) >> 5) << 2;
int i;
u64 pdpte;
u64 *pdpt;
int ret;
struct page *page;
u64 pdpte[ARRAY_SIZE(vcpu->pdptrs)];
spin_lock(&vcpu->kvm->lock);
page = gfn_to_page(vcpu->kvm, pdpt_gfn);
/* FIXME: !page - emulate? 0xff? */
pdpt = kmap_atomic(page, KM_USER0);
if (!page) {
ret = 0;
goto out;
}
ret = 1;
for (i = 0; i < 4; ++i) {
pdpte = pdpt[offset + i];
if ((pdpte & 1) && (pdpte & 0xfffffff0000001e6ull)) {
pdpt = kmap_atomic(page, KM_USER0);
memcpy(pdpte, pdpt+offset, sizeof(pdpte));
kunmap_atomic(pdpt, KM_USER0);
for (i = 0; i < ARRAY_SIZE(pdpte); ++i) {
if ((pdpte[i] & 1) && (pdpte[i] & 0xfffffff0000001e6ull)) {
ret = 0;
goto out;
}
}
ret = 1;
for (i = 0; i < 4; ++i)
vcpu->pdptrs[i] = pdpt[offset + i];
memcpy(vcpu->pdptrs, pdpte, sizeof(vcpu->pdptrs));
out:
kunmap_atomic(pdpt, KM_USER0);
spin_unlock(&vcpu->kvm->lock);
return ret;