From: Kyle Huey <me@kylehuey.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Nadav Amit" <nadav.amit@gmail.com>,
"Robert O'Callahan" <robert@ocallahan.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Andy Lutomirski" <luto@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>, "X86 ML" <x86@kernel.org>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Jeff Dike" <jdike@addtoit.com>,
"Richard Weinberger" <richard@nod.at>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Shuah Khan" <shuah@kernel.org>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Borislav Petkov" <bp@suse.de>,
"Peter Zijlstra" <peterz@infradead.org>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Len Brown" <len.brown@intel.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
"Dmitry Safonov" <dsafonov@virtuozzo.com>,
"David Matlack" <dmatlack@google.com>,
LKML <linux-kernel@vger.kernel.org>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-devel@lists.sourceforge.net>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-user@lists.sourceforge.net>,
"open list:FILESYSTEMS (VFS and infrastructure)"
<linux-fsdevel@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting
Date: Wed, 16 Nov 2016 17:59:30 -0800 [thread overview]
Message-ID: <CAP045ApYP6K1qtqKHEAbTR37Fdd+Gc8_-xiRMAK8XN5kzszspw@mail.gmail.com> (raw)
In-Reply-To: <1514461290.13216247.1479328935760.JavaMail.zimbra@redhat.com>
On Wed, Nov 16, 2016 at 12:42 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On Fri, Nov 11, 2016 at 12:54 PM, Nadav Amit <nadav.amit@gmail.com> wrote:
>> >
>> >> On Nov 10, 2016, at 3:40 PM, Kyle Huey <me@kylehuey.com> wrote:
>> >>
>> >> Hardware support for faulting on the cpuid instruction is not required to
>> >> emulate it, because cpuid triggers a VM exit anyways. KVM handles the
>> >> relevant
>> >> MSRs (MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLE) and upon a
>> >> cpuid-induced VM exit checks the cpuid faulting state and the CPL.
>> >> kvm_require_cpl is even kind enough to inject the GP fault for us.
>> >
>> > I think that for consistency you should also revise em_cpuid() of KVM
>> > instruction emulator. Otherwise it may be a potential security
>> > hazard (as far fetched as it currently seems).
>>
>> Hmm, ok. Do you know how I can test this code path?
>
> Try this patch (untested!)
Heh, yes, that would do it. Thanks!
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 5382b82462fc..06d940a7c9fa 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5868,8 +5868,7 @@ static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val)
>
> static int handle_cpuid(struct kvm_vcpu *vcpu)
> {
> - kvm_emulate_cpuid(vcpu);
> - return 1;
> + return emulate_instruction(vcpu, 0) == EMULATE_DONE;
> }
>
> static int handle_rdmsr(struct kvm_vcpu *vcpu)
>
> Paolo
- Kyle
prev parent reply other threads:[~2016-11-17 1:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-10 23:40 [PATCH v11 0/7] x86/arch_prctl Add ARCH_[GET|SET]_CPUID for controlling the CPUID instruction Kyle Huey
2016-11-10 23:40 ` [PATCH v11 1/7] x86/arch_prctl/64: Use SYSCALL_DEFINE2 to define sys_arch_prctl Kyle Huey
2016-11-10 23:40 ` [PATCH v11 2/7] x86/arch_prctl/64: Rename do_arch_prctl to do_arch_prctl_64 Kyle Huey
2016-11-10 23:40 ` [PATCH v11 3/7] x86/arch_prctl: Add do_arch_prctl_common Kyle Huey
2016-11-10 23:40 ` [PATCH v11 4/7] x86/syscalls/32: Wire up arch_prctl on x86-32 Kyle Huey
2016-11-10 23:40 ` [PATCH v11 5/7] x86/cpufeature: Detect CPUID faulting support Kyle Huey
2016-11-10 23:40 ` [PATCH v11 6/7] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID Kyle Huey
2016-11-11 1:25 ` kbuild test robot
2016-11-11 1:31 ` Kyle Huey
2016-11-10 23:40 ` [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting Kyle Huey
2016-11-11 20:54 ` Nadav Amit
2016-11-16 16:40 ` Kyle Huey
2016-11-16 20:42 ` Paolo Bonzini
2016-11-17 1:59 ` Kyle Huey [this message]
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