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Date: Fri, 25 Aug 2017 11:53:32 -0500
From: Brijesh Singh <brijesh.singh@....com>
To: Tom Lendacky <thomas.lendacky@....com>,
Paolo Bonzini <pbonzini@...hat.com>,
Stephen Rothwell <sfr@...b.auug.org.au>,
Radim Krčmář <rkrcmar@...hat.com>,
KVM <kvm@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: brijesh.singh@....com,
Linux-Next Mailing List <linux-next@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Yu Zhang <yu.c.zhang@...ux.intel.com>, paolo.bonzini@...il.com
Subject: Re: linux-next: manual merge of the kvm tree with the tip tree
Hi Paolo,
On 08/25/2017 08:57 AM, Tom Lendacky wrote:
> On 8/25/2017 1:39 AM, Paolo Bonzini wrote:
>> On 25/08/2017 06:39, Stephen Rothwell wrote:
>> 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 for the tip, I have expanded the patch to cover tdp cases and have verified
that it works fine with SME enabled KVM. If you are okay with this then I can
send patch.
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ccb70b8..7a8edc0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4109,16 +4109,30 @@ 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;
/*
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ccb70b8..7a8edc0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4109,16 +4109,30 @@ 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_gbpages(vcpu), is_pse(vcpu),
true);
+
+ if (!shadow_me_mask)
+ return;
+
+ 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;
+ shadow_zero_check->rsvd_bits_mask[i][2] &= ~shadow_me_mask;
+ shadow_zero_check->rsvd_bits_mask[i][3] &= ~shadow_me_mask;
+ }
+
}
EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask);
@@ -4136,8 +4150,13 @@ static void
reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
struct kvm_mmu *context)
{
+ struct rsvd_bits_validate *shadow_zero_check;
+ int i;
+
+ shadow_zero_check = &context->shadow_zero_check;
+
if (boot_cpu_is_amd())
- __reset_rsvds_bits_mask(vcpu, &context->shadow_zero_check,
+ __reset_rsvds_bits_mask(vcpu, shadow_zero_check,
boot_cpu_data.x86_phys_bits,
context->shadow_root_level, false,
boot_cpu_has(X86_FEATURE_GBPAGES),
@@ -4147,6 +4166,15 @@ reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
boot_cpu_data.x86_phys_bits,
false);
+ if (!shadow_me_mask)
+ return;
+
+ 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;
+ shadow_zero_check->rsvd_bits_mask[i][2] &= ~shadow_me_mask;
+ shadow_zero_check->rsvd_bits_mask[i][3] &= ~shadow_me_mask;
+ }
}
/*
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 3cc7255..d7d248a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -48,7 +48,7 @@
static inline u64 rsvd_bits(int s, int e)
{
- return __sme_clr(((1ULL << (e - s + 1)) - 1) << s);
+ return ((1ULL << (e - s + 1)) - 1) << s;
}
void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value);
> 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@...il.com too
>> because I'll be on vacation next week.
>>
>> (And thanks Stephen for the heads-up!)
>>
>> Paolo
>>
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