From: Paolo Bonzini <pbonzini@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
jmattson@google.com,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH 5/5] KVM: vmx: use MSR_IA32_TSX_CTRL to hard-disable TSX on guest that lack it
Date: Thu, 21 Nov 2019 10:05:04 +0100 [thread overview]
Message-ID: <4a820b71-79eb-7d71-9cd2-93954cefcdd2@redhat.com> (raw)
In-Reply-To: <20191121022252.GX3812@habkost.net>
On 21/11/19 03:22, Eduardo Habkost wrote:
> On Mon, Nov 18, 2019 at 07:17:47PM +0100, Paolo Bonzini wrote:
>> If X86_FEATURE_RTM is disabled, the guest should not be able to access
>> MSR_IA32_TSX_CTRL. We can therefore use it in KVM to force all
>> transactions from the guest to abort.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>
> So, without this patch guest OSes will incorrectly report "Not
> affected" at /sys/devices/system/cpu/vulnerabilities/tsx_async_abort
> if RTM is disabled in the VM configuration.
>
> Is there anything host userspace can do to detect this situation
> and issue a warning on that case?
>
> Is there anything the guest kernel can do to detect this and not
> report a false negative at /sys/.../tsx_async_abort?
Unfortunately not. The hypervisor needs to know about TAA in order to
mitigate it on behalf of the guest. At least this doesn't require an
updated userspace and VM configuration!
Paolo
prev parent reply other threads:[~2019-11-21 9:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 18:17 [PATCH 0/5] KVM: vmx: implement MSR_IA32_TSX_CTRL for guests Paolo Bonzini
2019-11-18 18:17 ` [PATCH 1/5] KVM: x86: fix presentation of TSX feature in ARCH_CAPABILITIES Paolo Bonzini
2019-11-18 19:39 ` Jim Mattson
2019-11-18 20:48 ` Jim Mattson
2019-11-22 20:15 ` Sean Christopherson
2019-11-18 18:17 ` [PATCH 2/5] KVM: x86: do not modify masked bits of shared MSRs Paolo Bonzini
2019-11-19 19:00 ` Jim Mattson
2019-11-18 18:17 ` [PATCH 3/5] KVM: x86: implement MSR_IA32_TSX_CTRL effect on CPUID Paolo Bonzini
2019-11-19 20:02 ` Jim Mattson
2019-11-18 18:17 ` [PATCH 4/5] KVM: vmx: implement MSR_IA32_TSX_CTRL disable RTM functionality Paolo Bonzini
2019-11-19 21:06 ` Jim Mattson
2019-11-20 12:21 ` Paolo Bonzini
2019-12-04 23:49 ` Jim Mattson
2019-12-05 10:16 ` Paolo Bonzini
2019-11-18 18:17 ` [PATCH 5/5] KVM: vmx: use MSR_IA32_TSX_CTRL to hard-disable TSX on guest that lack it Paolo Bonzini
2019-11-21 2:22 ` Eduardo Habkost
2019-11-21 9:05 ` Paolo Bonzini [this message]
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