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SubjectRe: linux-next: manual merge of the kvm tree with the tip tree
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On 8/25/2017 1:39 AM, Paolo Bonzini wrote:
> 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:

Thanks Paolo, Brijesh and I will test this and make sure everything works
properly with this patch.

Thanks,
Tom

>
> 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@gmail.com too
> because I'll be on vacation next week.
>
> (And thanks Stephen for the heads-up!)
>
> Paolo
>

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