[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <YAB7tckzbZUrRbf5@google.com>
Date: Thu, 14 Jan 2021 09:13:25 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v2 01/14] KVM: SVM: Zero out the VMCB array used to track
SEV ASID association
On Thu, Jan 14, 2021, Tom Lendacky wrote:
> On 1/13/21 6:36 PM, Sean Christopherson wrote:
> > Zero out the array of VMCB pointers so that pre_sev_run() won't see
> > garbage when querying the array to detect when an SEV ASID is being
> > associated with a new VMCB. In practice, reading random values is all
> > but guaranteed to be benign as a false negative (which is extremely
> > unlikely on its own) can only happen on CPU0 on the first VMRUN and would
> > only cause KVM to skip the ASID flush. For anything bad to happen, a
> > previous instance of KVM would have to exit without flushing the ASID,
> > _and_ KVM would have to not flush the ASID at any time while building the
> > new SEV guest.
> >
> > Cc: Borislav Petkov <bp@...e.de>
> > Cc: Tom Lendacky <thomas.lendacky@....com>
> > Cc: Brijesh Singh <brijesh.singh@....com>
> > Fixes: 70cd94e60c73 ("KVM: SVM: VMRUN should use associated ASID when SEV is enabled")
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> > arch/x86/kvm/svm/svm.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index 7ef171790d02..ccf52c5531fb 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -573,7 +573,7 @@ static int svm_cpu_init(int cpu)
> > if (svm_sev_enabled()) {
> > sd->sev_vmcbs = kmalloc_array(max_sev_asid + 1,
> > sizeof(void *),
> > - GFP_KERNEL);
> > + GFP_KERNEL | __GFP_ZERO);
>
> Alternatively, this call could just be changed to kcalloc().
Agreed, kcalloc() is a better option. I'll do that in v3.
Powered by blists - more mailing lists