[PATCH stable-5.4] KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

[PATCH stable-5.4] KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

[Jack Wang]

From: Maxim Levitsky <mlevitsk@redhat.com>

This msr is only available when the host supports WAITPKG feature.

This breaks a nested guest, if the L1 hypervisor is set to ignore
unknown msrs, because the only other safety check that the
kernel does is that it attempts to read the msr and
rejects it if it gets an exception.

Cc: stable@vger.kernel.org
Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a
use boot_cpu_has for checking the feature)
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
---
 arch/x86/kvm/x86.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 708b37274cb5..4cacf4669235 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5226,6 +5226,10 @@ static void kvm_init_msr_list(void)
 			if (!kvm_x86_ops->rdtscp_supported())
 				continue;
 			break;
+		case MSR_IA32_UMWAIT_CONTROL:
+			if (!boot_cpu_has(X86_FEATURE_WAITPKG))
+				continue;
+			break;
 		case MSR_IA32_RTIT_CTL:
 		case MSR_IA32_RTIT_STATUS:
 			if (!kvm_x86_ops->pt_supported())
-- 
2.25.1

Re: [PATCH stable-5.4] KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

[Paolo Bonzini]

On 11/11/20 14:20, Jack Wang wrote:
> From: Maxim Levitsky <mlevitsk@redhat.com>
> 
> This msr is only available when the host supports WAITPKG feature.
> 
> This breaks a nested guest, if the L1 hypervisor is set to ignore
> unknown msrs, because the only other safety check that the
> kernel does is that it attempts to read the msr and
> rejects it if it gets an exception.
> 
> Cc: stable@vger.kernel.org
> Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com>
> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> (cherry picked from commit f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a
> use boot_cpu_has for checking the feature)
> Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
> ---
>   arch/x86/kvm/x86.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 708b37274cb5..4cacf4669235 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5226,6 +5226,10 @@ static void kvm_init_msr_list(void)
>   			if (!kvm_x86_ops->rdtscp_supported())
>   				continue;
>   			break;
> +		case MSR_IA32_UMWAIT_CONTROL:
> +			if (!boot_cpu_has(X86_FEATURE_WAITPKG))
> +				continue;
> +			break;
>   		case MSR_IA32_RTIT_CTL:
>   		case MSR_IA32_RTIT_STATUS:
>   			if (!kvm_x86_ops->pt_supported())
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks,

Paolo

Re: [PATCH stable-5.4] KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

[Sasha Levin]

On Wed, Nov 11, 2020 at 02:51:12PM +0100, Paolo Bonzini wrote:
>On 11/11/20 14:20, Jack Wang wrote:
>>From: Maxim Levitsky <mlevitsk@redhat.com>
>>
>>This msr is only available when the host supports WAITPKG feature.
>>
>>This breaks a nested guest, if the L1 hypervisor is set to ignore
>>unknown msrs, because the only other safety check that the
>>kernel does is that it attempts to read the msr and
>>rejects it if it gets an exception.
>>
>>Cc: stable@vger.kernel.org
>>Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
>>Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>>Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com>
>>Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
>>Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>(cherry picked from commit f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a
>>use boot_cpu_has for checking the feature)
>>Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
>>---
>>  arch/x86/kvm/x86.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>index 708b37274cb5..4cacf4669235 100644
>>--- a/arch/x86/kvm/x86.c
>>+++ b/arch/x86/kvm/x86.c
>>@@ -5226,6 +5226,10 @@ static void kvm_init_msr_list(void)
>>  			if (!kvm_x86_ops->rdtscp_supported())
>>  				continue;
>>  			break;
>>+		case MSR_IA32_UMWAIT_CONTROL:
>>+			if (!boot_cpu_has(X86_FEATURE_WAITPKG))
>>+				continue;
>>+			break;
>>  		case MSR_IA32_RTIT_CTL:
>>  		case MSR_IA32_RTIT_STATUS:
>>  			if (!kvm_x86_ops->pt_supported())
>>
>
>Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Queued up, thanks!

-- 
Thanks,
Sasha