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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Jim Mattson" <jmattson@google.com>
Subject: Re: [PATCH 3/5] x86: KVM: svm: clear interrupt shadow on all paths in skip_emulated_instruction()
Date: Thu, 01 Aug 2019 16:43:05 +0200	[thread overview]
Message-ID: <87ftml54li.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20190801141802.GA6783@linux.intel.com>

Sean Christopherson <sean.j.christopherson@intel.com> writes:

> On Thu, Aug 01, 2019 at 07:14:16AM +0200, Vitaly Kuznetsov wrote:
>> Regardless of the way how we skip instruction, interrupt shadow needs to be
>> cleared.
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Reviewed-by: Jim Mattson <jmattson@google.com>
>> ---
>>  arch/x86/kvm/svm.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 80f576e05112..7c7dff3f461f 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -784,13 +784,15 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
>>  				EMULATE_DONE)
>>  			pr_err_once("KVM: %s: unable to skip instruction\n",
>>  				    __func__);
>> -		return;
>> +		goto clear_int_shadow;
>
> A better fix would be to clear the interrupt shadow in x86_emulate_instruction()
> after updating RIP for EMULTYPE_SKIP.  VMX has this same flaw when running
> nested as handle_ept_misconfig() also expects the interrupt shadow to be
> handled by kvm_emulate_instruction().  Clearing the shadow if and only if
> the skipping is successful also means KVM isn't incorrectly zapping the
> shadow when emulation fails.

Oh, nice catch actually! Will do in v2.

-- 
Vitaly

  reply	other threads:[~2019-08-01 14:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01  5:14 [PATCH 0/5] x86: KVM: svm: get rid of hardcoded instructions lengths Vitaly Kuznetsov
2019-08-01  5:14 ` [PATCH 1/5] x86: KVM: svm: don't pretend to advance RIP in case wrmsr_interception() results in #GP Vitaly Kuznetsov
2019-08-01  5:14 ` [PATCH 2/5] x86: KVM: svm: avoid flooding logs when skip_emulated_instruction() fails Vitaly Kuznetsov
2019-08-01  5:14 ` [PATCH 3/5] x86: KVM: svm: clear interrupt shadow on all paths in skip_emulated_instruction() Vitaly Kuznetsov
2019-08-01 14:18   ` Sean Christopherson
2019-08-01 14:43     ` Vitaly Kuznetsov [this message]
2019-08-01  5:14 ` [PATCH 4/5] x86: KVM: add xsetbv to the emulator Vitaly Kuznetsov
2019-08-01  5:14 ` [PATCH 5/5] x86: KVM: svm: remove hardcoded instruction length from intercepts Vitaly Kuznetsov

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