From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: KarimAllah Ahmed <karahmed@amazon.com>,
KarimAllah Ahmed <karahmed@amazon.de>,
kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Asit Mallick <asit.k.mallick@intel.com>,
Arjan Van De Ven <arjan.van.de.ven@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dan Williams <dan.j.williams@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Greg KH <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.org>,
Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH v3 4/4] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL
Date: Tue, 30 Jan 2018 19:56:27 -0500 [thread overview]
Message-ID: <e3cbb848-a6b2-5a2b-7623-cdfbc6769d13@redhat.com> (raw)
In-Reply-To: <CALMp9eTu0R+e8WFGzzD0zmSKsgPTYSvw6Ot7vyLjP5yJi36deQ@mail.gmail.com>
On 30/01/2018 19:27, Jim Mattson wrote:
> On Tue, Jan 30, 2018 at 4:19 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> The new code in nested_vmx_merge_msr_bitmap should be conditional on
>> vmx->save_spec_ctrl_on_exit.
>
> But then if L1 doesn't use MSR_IA32_SPEC_CTRL itself and it uses the
> VM-entry MSR load list to set up L2's MSR_IA32_SPEC_CTRL, you will
> never set vmx->save_spec_ctrl_on_exit, and L2's accesses to the MSR
> will always be intercepted by L0.
If you don't make it conditional, L0 will forget to read back at vmexit
what value L2 has written to the MSR. The alternative is to set
vmx->save_spec_ctrl_on_exit on all writes, including those coming from
L2. That works for me.
Paolo
next prev parent reply other threads:[~2018-01-31 0:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 0:10 [PATCH v3 0/4] KVM: Expose speculation control feature to guests KarimAllah Ahmed
2018-01-30 0:10 ` [PATCH v3 1/4] KVM: x86: Update the reverse_cpuid list to include CPUID_7_EDX KarimAllah Ahmed
2018-01-30 23:17 ` Paolo Bonzini
2018-01-30 0:10 ` [PATCH v3 2/4] KVM: x86: Add IBPB support KarimAllah Ahmed
2018-01-30 14:22 ` Tom Lendacky
2018-01-30 14:36 ` David Woodhouse
2018-01-30 17:19 ` Jim Mattson
2018-01-30 17:43 ` David Woodhouse
2018-01-30 0:10 ` [PATCH v3 3/4] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES KarimAllah Ahmed
2018-01-30 0:22 ` Raj, Ashok
2018-01-30 0:25 ` KarimAllah Ahmed
2018-01-30 23:21 ` Paolo Bonzini
2018-01-30 0:10 ` [PATCH v3 4/4] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL KarimAllah Ahmed
2018-01-30 17:49 ` Jim Mattson
2018-01-30 21:00 ` KarimAllah Ahmed
2018-01-30 22:49 ` Jim Mattson
2018-01-30 23:32 ` Paolo Bonzini
2018-01-30 23:50 ` KarimAllah Ahmed
2018-01-31 0:16 ` Jim Mattson
2018-01-31 0:19 ` Paolo Bonzini
2018-01-31 0:27 ` Jim Mattson
2018-01-31 0:52 ` KarimAllah Ahmed
2018-01-31 0:56 ` Paolo Bonzini [this message]
2018-01-30 9:00 ` [PATCH v3 0/4] KVM: Expose speculation control feature to guests David Woodhouse
2018-01-30 9:32 ` KarimAllah Ahmed
2018-01-30 23:36 ` Paolo Bonzini
2018-01-30 23:48 ` Raj, Ashok
2018-01-31 0:16 ` Paolo Bonzini
2018-01-31 0:26 ` David Woodhouse
2018-01-31 6:54 ` Dave Hansen
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