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Date:   Wed, 20 Nov 2019 23:22:52 -0300
From:   Eduardo Habkost <ehabkost@redhat.com>
To:     Paolo Bonzini <pbonzini@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
Message-ID: <20191121022252.GX3812@habkost.net>
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 <1574101067-5638-6-git-send-email-pbonzini@redhat.com>
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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.
>=20
> 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?

--=20
Eduardo