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From: Maxim Levitsky <mlevitsk@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Reiji Watanabe <reijiw@google.com>
Subject: Re: [PATCH 11/15] KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way
Date: Mon, 10 May 2021 11:26:31 +0300	[thread overview]
Message-ID: <a8595d87b67616a7ac25784c6acdebbd170d2f5a.camel@redhat.com> (raw)
In-Reply-To: <20210504171734.1434054-12-seanjc@google.com>

On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> Tag TSX_CTRL as not needing to be loaded when RTM isn't supported in the
> host.  Crushing the write mask to '0' has the same effect, but requires
> more mental gymnastics to understand.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 22 ++++++++++------------
>  1 file changed, 10 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 4b432d2bbd06..7a53568b34fc 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1771,7 +1771,13 @@ static void setup_msrs(struct vcpu_vmx *vmx)
>  			   guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP) ||
>  			   guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDPID));
>  
> -	vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL, true);
> +	/*
> +	 * hle=0, rtm=0, tsx_ctrl=1 can be found with some combinations of new
> +	 * kernel and old userspace.  If those guests run on a tsx=off host, do
> +	 * allow guests to use TSX_CTRL, but don't change the value in hardware
> +	 * so that TSX remains always disabled.
> +	 */
> +	vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL, boot_cpu_has(X86_FEATURE_RTM));
>  
>  	if (cpu_has_vmx_msr_bitmap())
>  		vmx_update_msr_bitmap(&vmx->vcpu);
> @@ -6919,23 +6925,15 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
>  		vmx->guest_uret_msrs[i].data = 0;
>  		vmx->guest_uret_msrs[i].mask = -1ull;
>  	}
> -	tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL);
> -	if (tsx_ctrl) {
> +	if (boot_cpu_has(X86_FEATURE_RTM)) {
>  		/*
>  		 * TSX_CTRL_CPUID_CLEAR is handled in the CPUID interception.
>  		 * Keep the host value unchanged to avoid changing CPUID bits
>  		 * under the host kernel's feet.
> -		 *
> -		 * hle=0, rtm=0, tsx_ctrl=1 can be found with some combinations
> -		 * of new kernel and old userspace.  If those guests run on a
> -		 * tsx=off host, do allow guests to use TSX_CTRL, but do not
> -		 * change the value on the host so that TSX remains always
> -		 * disabled.
>  		 */
> -		if (boot_cpu_has(X86_FEATURE_RTM))
> +		tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL);
> +		if (tsx_ctrl)
>  			vmx->guest_uret_msrs[i].mask = ~(u64)TSX_CTRL_CPUID_CLEAR;
> -		else
> -			vmx->guest_uret_msrs[i].mask = 0;
>  	}
>  
>  	err = alloc_loaded_vmcs(&vmx->vmcs01);

I also agree that commit message should be updated as Paolo said,
but other than that:

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky <mlevitsk@redhat.com>




  parent reply	other threads:[~2021-05-10  8:26 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04 17:17 [PATCH 00/15] KVM: x86: RDPID/RDTSCP fixes and uret MSR cleanups Sean Christopherson
2021-05-04 17:17 ` [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE_RDTSCP control is unsupported Sean Christopherson
2021-05-04 17:37   ` Jim Mattson
2021-05-04 17:53     ` Jim Mattson
2021-05-04 18:14       ` Sean Christopherson
2021-05-05  3:04   ` Reiji Watanabe
2021-05-10  8:03   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 02/15] KVM: x86: Emulate RDPID only if RDTSCP is supported Sean Christopherson
2021-05-04 17:50   ` Jim Mattson
2021-05-05  3:51   ` Reiji Watanabe
2021-05-05  8:01     ` Paolo Bonzini
2021-05-10  8:08   ` Maxim Levitsky
2021-05-10 17:20     ` Sean Christopherson
2021-05-11 12:32       ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be disabled in the guest Sean Christopherson
2021-05-04 21:45   ` Jim Mattson
2021-05-04 21:53     ` Sean Christopherson
2021-05-04 21:56       ` Jim Mattson
2021-05-04 22:10         ` Sean Christopherson
2021-05-04 22:24           ` Jim Mattson
2021-05-04 21:57       ` Paolo Bonzini
2021-05-04 21:58         ` Jim Mattson
2021-05-10  8:08           ` Maxim Levitsky
2021-05-10 16:56             ` Sean Christopherson
2021-05-11 12:34               ` Maxim Levitsky
2021-05-18 10:59               ` Paolo Bonzini
2021-05-18 19:24                 ` Sean Christopherson
2021-05-05  4:26   ` Reiji Watanabe
2021-05-10  8:08   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 04/15] KVM: x86: Move RDPID emulation intercept to its own enum Sean Christopherson
2021-05-04 23:24   ` Jim Mattson
2021-05-10  8:14   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 05/15] KVM: VMX: Disable preemption when probing user return MSRs Sean Christopherson
2021-05-04 23:36   ` Jim Mattson
2021-05-10  8:18   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 06/15] KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host Sean Christopherson
2021-05-10  8:20   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 07/15] KVM: x86: Add support for RDPID without RDTSCP Sean Christopherson
2021-05-10  8:20   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 08/15] KVM: VMX: Configure list of user return MSRs at module init Sean Christopherson
2021-05-10  8:23   ` Maxim Levitsky
2021-05-10 15:13     ` Sean Christopherson
2021-05-11 12:34       ` Maxim Levitsky
2021-05-11 20:10         ` Sean Christopherson
2021-05-04 17:17 ` [PATCH 09/15] KVM: VMX: Use flag to indicate "active" uret MSRs instead of sorting list Sean Christopherson
2021-05-08  3:31   ` Reiji Watanabe
2021-05-10 16:43     ` Sean Christopherson
2021-05-10 17:55       ` Reiji Watanabe
2021-05-10  8:25   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 10/15] KVM: VMX: Use common x86's uret MSR list as the one true list Sean Christopherson
2021-05-10  8:25   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 11/15] KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way Sean Christopherson
2021-05-05  8:49   ` Paolo Bonzini
2021-05-05 15:36     ` Sean Christopherson
2021-05-05 15:50       ` Paolo Bonzini
2021-05-10  8:26   ` Maxim Levitsky [this message]
2021-05-04 17:17 ` [PATCH 12/15] KVM: x86: Export the number of uret MSRs to vendor modules Sean Christopherson
2021-05-10  8:27   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 13/15] KVM: x86: Move uret MSR slot management to common x86 Sean Christopherson
2021-05-10  8:28   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 14/15] KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model Sean Christopherson
2021-05-10  8:29   ` Maxim Levitsky
2021-05-10 16:50     ` Sean Christopherson
2021-05-10 17:11       ` Jim Mattson
2021-05-11 12:34         ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 15/15] KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed Sean Christopherson
2021-05-10  8:29   ` Maxim Levitsky
2021-05-05  8:51 ` [PATCH 00/15] KVM: x86: RDPID/RDTSCP fixes and uret MSR cleanups Paolo Bonzini

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