From: Jim Mattson <jmattson@google.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: "kvm list" <kvm@vger.kernel.org>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [PATCH 2/4] KVM: nVMX: Check GUEST_DR7 on vmentry of nested guests
Date: Fri, 20 Dec 2019 15:45:32 -0800 [thread overview]
Message-ID: <CALMp9eR2GQ_aerH-arOEpa08k8ZdtYCA5ftxHfDCo5fS1r3VtA@mail.gmail.com> (raw)
In-Reply-To: <CALMp9eTBPRT+Re9rZzmutAiy62qSMQRfMrnyiYkNHkCKDy-KPQ@mail.gmail.com>
On Fri, Aug 30, 2019 at 4:15 PM Jim Mattson <jmattson@google.com> wrote:
>
> On Fri, Aug 30, 2019 at 4:07 PM Krish Sadhukhan
> <krish.sadhukhan@oracle.com> wrote:
> >
> >
> >
> > On 08/29/2019 03:26 PM, Jim Mattson wrote:
> > > On Thu, Aug 29, 2019 at 2:25 PM Krish Sadhukhan
> > > <krish.sadhukhan@oracle.com> wrote:
> > >> According to section "Checks on Guest Control Registers, Debug Registers, and
> > >> and MSRs" in Intel SDM vol 3C, the following checks are performed on vmentry
> > >> of nested guests:
> > >>
> > >> If the "load debug controls" VM-entry control is 1, bits 63:32 in the DR7
> > >> field must be 0.
> > > Can't we just let the hardware check guest DR7? This results in
> > > "VM-entry failure due to invalid guest state," right? And we just
> > > reflect that to L1?
> >
> > Just trying to understand the reason why this particular check can be
> > deferred to the hardware.
>
> The vmcs02 field has the same value as the vmcs12 field, and the
> physical CPU has the same requirements as the virtual CPU.
Sadly, I was mistaken. The guest DR7 value is not transferred from
vmcs12 to vmcs02. It is set prior to the vmcs02 VM-entry by
kvm_set_dr(). Unfortunately, that function synthesizes a #GP if any
bit in the high dword of DR7 is set. So, you are correct, Krish: this
field must be checked in software.
next prev parent reply other threads:[~2019-12-20 23:45 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 20:56 [PATCH 0/4] KVM: nVMX: Check GUEST_DEBUGCTL and GUEST_DR7 on vmentry of nested guests Krish Sadhukhan
2019-08-29 20:56 ` [PATCH 1/4] KVM: nVMX: Check GUEST_DEBUGCTL " Krish Sadhukhan
2019-08-29 22:12 ` Jim Mattson
2019-08-30 23:26 ` Krish Sadhukhan
2019-09-01 23:55 ` Jim Mattson
2019-08-29 20:56 ` [PATCH 2/4] KVM: nVMX: Check GUEST_DR7 " Krish Sadhukhan
2019-08-29 22:26 ` Jim Mattson
2019-08-30 23:07 ` Krish Sadhukhan
2019-08-30 23:15 ` Jim Mattson
2019-09-02 0:33 ` Jim Mattson
[not found] ` <e229bea2-acb2-e268-6281-d8e467c3282e@oracle.com>
2019-09-04 16:44 ` Jim Mattson
2019-09-04 16:58 ` Sean Christopherson
2019-09-04 18:05 ` Krish Sadhukhan
2019-09-04 18:20 ` Jim Mattson
2019-09-09 4:11 ` Krish Sadhukhan
2019-09-09 15:56 ` Jim Mattson
2019-09-04 17:14 ` Sean Christopherson
2019-12-20 23:45 ` Jim Mattson [this message]
2019-12-21 0:27 ` Jim Mattson
2019-08-29 20:56 ` [PATCH 3/4] kvm-unit-test: nVMX: __enter_guest() should not set "launched" state when VM-entry fails Krish Sadhukhan
2019-09-04 15:42 ` Sean Christopherson
2019-09-13 20:37 ` Krish Sadhukhan
2019-09-13 21:06 ` Sean Christopherson
2019-09-16 19:12 ` Krish Sadhukhan
2019-08-29 20:56 ` [PATCH 4/4] kvm-unit-test: nVMX: Check GUEST_DEBUGCTL and GUEST_DR7 on vmentry of nested guests Krish Sadhukhan
2019-08-29 23:17 ` Jim Mattson
2019-08-30 1:12 ` Nadav Amit
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