On 25/08/2017 06:39, Stephen Rothwell wrote:
> Hi all,
>
> Today's linux-next merge of the kvm tree got a conflict in:
>
> arch/x86/kvm/mmu.h
>
> between commit:
>
> d0ec49d4de90 ("kvm/x86/svm: Support Secure Memory Encryption within KVM")
>
> from the tip tree and commit:
>
> d1cd3ce90044 ("KVM: MMU: check guest CR3 reserved bits based on its physical address width.")
>
> from the kvm tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
>
Thomas L., Ingo,
this is completely wrong:
>
> static inline u64 rsvd_bits(int s, int e)
> {
> - return ((1ULL << (e - s + 1)) - 1) << s;
> + return __sme_clr(((1ULL << (e - s + 1)) - 1) << s);
> }
>
First, rsvd_bits is just a simple function to return some 1 bits. Applying
a mask based on properties of the host MMU is incorrect.
Second, the masks computed by __reset_rsvds_bits_mask also apply to
guest page tables, where the C bit is reserved since we don't emulate
SME.
Something like this:
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2dafd36368cc..e0597d703d72 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4142,16 +4142,24 @@ void
reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
{
bool uses_nx = context->nx || context->base_role.smep_andnot_wp;
+ struct rsvd_bits_validate *shadow_zero_check;
+ int i;
/*
* Passing "true" to the last argument is okay; it adds a check
* on bit 8 of the SPTEs which KVM doesn't use anyway.
*/
- __reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check,
+ shadow_zero_check = &context->shadow_zero_check;
+ __reset_rsvds_bits_mask(vcpu, shadow_zero_check,
boot_cpu_data.x86_phys_bits,
context->shadow_root_level, uses_nx,
guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES),
is_pse(vcpu), true);
+
+ for (i = context->shadow_root_level; --i >= 0; ) {
+ shadow_zero_check->rsvd_bits_mask[i][0] &= ~shadow_me_mask;
+ shadow_zero_check->rsvd_bits_mask[i][1] &= ~shadow_me_mask;
+ }
}
EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask);
Can you please fix it up? Please Cc me at paolo.bonzini@xxxxxxxxx too
because I'll be on vacation next week.
(And thanks Stephen for the heads-up!)
Paolo
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