From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Nathan Chancellor <nathan@kernel.org>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH 5/6] KVM: x86: Virtualize FLUSH_L1D and passthrough MSR_IA32_FLUSH_CMD
Date: Mon, 27 Mar 2023 11:33:31 +0800 [thread overview]
Message-ID: <373823f7-00ba-070c-53c7-384d29889e40@intel.com> (raw)
In-Reply-To: <20230322011440.2195485-6-seanjc@google.com>
On 3/22/2023 9:14 AM, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c83ec88da043..3c58dbae7b4c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3628,6 +3628,18 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>
> wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
> break;
> + case MSR_IA32_FLUSH_CMD:
> + if (!msr_info->host_initiated &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_FLUSH_L1D))
> + return 1;
> +
> + if (!boot_cpu_has(X86_FEATURE_FLUSH_L1D) || (data & ~L1D_FLUSH))
> + return 1;
> + if (!data)
> + break;
> +
> + wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
> + break;
Then KVM provides the ability to flush the L1 data cache of host to
userspace. Can it be exploited to degrade the host performance if
userspace VMM keeps flushing the L1 data cache?
next prev parent reply other threads:[~2023-03-27 3:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-22 1:14 [PATCH 0/6] KVM: x86: Unhost the *_CMD MSR mess Sean Christopherson
2023-03-22 1:14 ` [PATCH 1/6] KVM: x86: Revert MSR_IA32_FLUSH_CMD.FLUSH_L1D enabling Sean Christopherson
2023-03-22 8:15 ` Mathias Krause
2023-03-22 1:14 ` [PATCH 2/6] KVM: VMX: Passthrough MSR_IA32_PRED_CMD based purely on host+guest CPUID Sean Christopherson
2023-03-27 3:46 ` Xiaoyao Li
2023-03-22 1:14 ` [PATCH 3/6] KVM: SVM: " Sean Christopherson
2023-03-22 1:14 ` [PATCH 4/6] KVM: x86: Move MSR_IA32_PRED_CMD WRMSR emulation to common code Sean Christopherson
2023-03-27 6:41 ` Xiaoyao Li
2023-03-22 1:14 ` [PATCH 5/6] KVM: x86: Virtualize FLUSH_L1D and passthrough MSR_IA32_FLUSH_CMD Sean Christopherson
2023-03-23 5:07 ` Pawan Gupta
2023-03-23 22:17 ` Sean Christopherson
2023-03-24 8:48 ` Zhi Wang
2023-03-27 3:33 ` Xiaoyao Li [this message]
2023-03-27 15:37 ` Jim Mattson
2023-03-27 16:00 ` Sean Christopherson
2023-03-22 1:14 ` [PATCH 6/6] KVM: SVM: Return the local "r" variable from svm_set_msr() Sean Christopherson
2023-03-23 22:46 ` [PATCH 0/6] KVM: x86: Unhost the *_CMD MSR mess Sean Christopherson
2023-03-27 15:19 ` Paolo Bonzini
2023-03-27 15:28 ` Sean Christopherson
2023-03-27 15:46 ` Paolo Bonzini
2023-04-12 19:49 ` Paolo Bonzini
2023-04-12 20:00 ` Sean Christopherson
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