From: John Allen <john.allen@amd.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, rkrcmar@redhat.com
Subject: Re: [PATCH] kvm/svm: PKU not currently supported
Date: Thu, 19 Dec 2019 13:49:48 -0600 [thread overview]
Message-ID: <20191219194948.adug277luzjdu3qv@mojo.amd.com> (raw)
In-Reply-To: <87immc873u.fsf@vitty.brq.redhat.com>
On Thu, Dec 19, 2019 at 08:09:57PM +0100, Vitaly Kuznetsov wrote:
> John Allen <john.allen@amd.com> writes:
>
> > Current SVM implementation does not have support for handling PKU. Guests
> > running on a host with future AMD cpus that support the feature will read
> > garbage from the PKRU register and will hit segmentation faults on boot as
> > memory is getting marked as protected that should not be. Ensure that cpuid
> > from SVM does not advertise the feature.
> >
> > Signed-off-by: John Allen <john.allen@amd.com>
> > ---
> > arch/x86/kvm/svm.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index 122d4ce3b1ab..f911aa1b41c8 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -5933,6 +5933,8 @@ static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> > if (avic)
> > entry->ecx &= ~bit(X86_FEATURE_X2APIC);
> > break;
> > + case 0x7:
> > + entry->ecx &= ~bit(X86_FEATURE_PKU);
>
> Would it make more sense to introduce kvm_x86_ops->pku_supported() (and
> return false for SVM and boot_cpu_has(X86_FEATURE_PKU) for vmx) so we
> don't set the bit in the first place?
Yes, I think you're right. I had initially planned to do it that way so I
already have a patch ready. I'll send it up pronto.
>
> > case 0x80000001:
> > if (nested)
> > entry->ecx |= (1 << 2); /* Set SVM bit */
>
> --
> Vitaly
>
prev parent reply other threads:[~2019-12-19 19:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-19 15:23 [PATCH] kvm/svm: PKU not currently supported John Allen
2019-12-19 19:09 ` Vitaly Kuznetsov
2019-12-19 19:49 ` John Allen [this message]
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