From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: "jmattson@google.com" <jmattson@google.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"arjan.van.de.ven@intel.com" <arjan.van.de.ven@intel.com>,
"ashok.raj@intel.com" <ashok.raj@intel.com>,
"Raslan, KarimAllah" <karahmed@amazon.de>,
"Raslan, KarimAllah" <karahmed@amazon.de>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"aarcange@redhat.com" <aarcange@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"dave.hansen@intel.com" <dave.hansen@intel.com>,
"asit.k.mallick@intel.com" <asit.k.mallick@intel.com>,
"jun.nakajima@intel.com" <jun.nakajima@intel.com>
Subject: Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL
Date: Wed, 31 Jan 2018 21:17:46 +0000 [thread overview]
Message-ID: <1517433465.18619.209.camel@amazon.co.uk> (raw)
In-Reply-To: <CALMp9eQ5fbfnqCvs_dMhoTOGTDX-+yt6QtJdUfiQg1BXq-0P3A@mail.gmail.com>
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On Wed, 2018-01-31 at 13:05 -0800, Jim Mattson wrote:
> On Wed, Jan 31, 2018 at 1:00 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> > Yes, but how would moving the field into struct loaded_vmcs do anything?
> > Only vmon/vmoff would change anything in vmx->nested.vmcs02.
>
> My suggestion was that nested_vmx_merge_msr_bitmap should set the
> vmcs02 version of save_spec_ctrl_on_exit based on the calculated value
> of the write permission bit for IA32_SPEC_CTRL in the vmcs02 MSR
> permission bitmap.
>
> > Even then, L1 vmexits will also be penalized because L1 has probably
> > done an RDMSR/WRMSR on L2->L1 vmexit. So I don't think it's an issue?
>
> Yes, it sucks to be L1 in this situation.
Well... we *could* clear the save_spec_ctrl_on_exit flag and intercept
the MSR again, any time that the actual value of spec_ctrl is zero.
I don't think we'd want to do that too aggressively, but there might be
something we could do there.
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Amazon Web Services UK Limited. Registered in England and Wales with registration number 08650665 and which has its registered office at 60 Holborn Viaduct, London EC1A 2FD, United Kingdom.
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next prev parent reply other threads:[~2018-01-31 21:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-31 19:37 [PATCH v5 0/5] KVM: Expose speculation control feature to guests KarimAllah Ahmed
2018-01-31 19:37 ` [PATCH v5 1/5] KVM: x86: Update the reverse_cpuid list to include CPUID_7_EDX KarimAllah Ahmed
2018-01-31 20:22 ` Konrad Rzeszutek Wilk
2018-01-31 19:37 ` [PATCH v5 2/5] KVM: x86: Add IBPB support KarimAllah Ahmed
2018-01-31 19:45 ` Jim Mattson
2018-01-31 19:53 ` David Woodhouse
2018-01-31 19:55 ` Jim Mattson
2018-02-01 0:27 ` KarimAllah Ahmed
2018-01-31 20:28 ` Konrad Rzeszutek Wilk
2018-01-31 20:36 ` KarimAllah Ahmed
2018-02-01 4:54 ` Tom Lendacky
2018-02-01 17:00 ` Raj, Ashok
2018-01-31 19:37 ` [PATCH v5 3/5] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES KarimAllah Ahmed
2018-01-31 19:37 ` [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL KarimAllah Ahmed
2018-01-31 19:53 ` Jim Mattson
2018-01-31 20:00 ` David Woodhouse
2018-01-31 20:01 ` KarimAllah Ahmed
2018-01-31 20:18 ` Jim Mattson
2018-01-31 20:21 ` David Woodhouse
2018-01-31 21:18 ` Jim Mattson
2018-01-31 22:05 ` David Woodhouse
2018-01-31 20:34 ` Paolo Bonzini
2018-01-31 20:54 ` Jim Mattson
2018-01-31 21:00 ` Paolo Bonzini
2018-01-31 21:05 ` Jim Mattson
2018-01-31 21:17 ` Woodhouse, David [this message]
2018-01-31 21:42 ` Paolo Bonzini
2018-01-31 21:53 ` Jim Mattson
2018-01-31 21:59 ` Paolo Bonzini
2018-01-31 21:59 ` David Woodhouse
2018-01-31 22:06 ` Jim Mattson
2018-01-31 22:10 ` David Woodhouse
2018-01-31 22:21 ` Linus Torvalds
2018-01-31 22:53 ` Andy Lutomirski
2018-02-01 14:09 ` Paolo Bonzini
2018-01-31 22:52 ` KarimAllah Ahmed
2018-02-01 0:24 ` KarimAllah Ahmed
2018-02-01 4:26 ` Konrad Rzeszutek Wilk
2018-02-01 13:25 ` David Woodhouse
2018-02-01 17:37 ` KarimAllah Ahmed
2018-02-01 17:46 ` KarimAllah Ahmed
2018-02-01 14:19 ` Konrad Rzeszutek Wilk
2018-02-01 14:28 ` KarimAllah Ahmed
2018-01-31 22:56 ` Raj, Ashok
2018-01-31 19:37 ` [PATCH v5 5/5] KVM: SVM: " KarimAllah Ahmed
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