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From: Tom Lendacky <thomas.lendacky@amd.com>
To: "Woodhouse, David" <dwmw@amazon.co.uk>,
	Borislav Petkov <bp@alien8.de>, Ashok Raj <ashok.raj@intel.com>
Cc: linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andi Kleen <ak@linux.intel.com>,
	Arjan Van De Ven <arjan.van.de.ven@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>
Subject: Re: [PATCH 5/5] x86/feature: Detect the x86 feature Indirect Branch Prediction Barrier
Date: Fri, 12 Jan 2018 09:21:53 -0600	[thread overview]
Message-ID: <231ac995-0a8f-c55a-1800-5b71a1719a0f@amd.com> (raw)
In-Reply-To: <1515760769.22302.445.camel@amazon.co.uk>

On 1/12/2018 6:39 AM, Woodhouse, David wrote:
> On Fri, 2018-01-12 at 13:32 +0100, Borislav Petkov wrote:
>> On Thu, Jan 11, 2018 at 05:32:19PM -0800, Ashok Raj wrote:
>>> cpuid ax=0x7, return rdx bit 26 to indicate presence of both
>>> IA32_SPEC_CTRL(MSR 0x48) and IA32_PRED_CMD(MSR 0x49)
>>
>> So why do we need two X86_FEATURE flags then?
> 
> AMD has only the latter and enumerates them differently.

Correct.  Both 0x48 and 0x49 are tied to the same cpuid bit.  AMD has
a separate cpuid bit for 0x49 (IBPB) alone.

Thanks,
Tom

> 

  reply	other threads:[~2018-01-12 15:22 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-12  1:32 [PATCH 0/5] Add support for IBRS & IBPB KVM support Ashok Raj
2018-01-12  1:32 ` [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native_wrmsrl Ashok Raj
2018-01-12  1:41   ` Andy Lutomirski
2018-01-12  1:52     ` Raj, Ashok
2018-01-12  2:20       ` Andy Lutomirski
2018-01-12  3:01         ` Raj, Ashok
2018-01-12  5:03           ` Dave Hansen
2018-01-12 16:28             ` Josh Poimboeuf
2018-01-12 16:28             ` Woodhouse, David
2018-01-13  6:20             ` Andy Lutomirski
2018-01-13 13:52               ` Van De Ven, Arjan
2018-01-13 15:20                 ` Andy Lutomirski
2018-01-13  6:19           ` Andy Lutomirski
2018-01-12  7:54   ` Greg KH
2018-01-12 12:28   ` Borislav Petkov
2018-01-12  1:32 ` [PATCH 2/5] x86/ibrs: Add new helper macros to save/restore MSR_IA32_SPEC_CTRL Ashok Raj
2018-01-12  1:32 ` [PATCH 3/5] x86/ibrs: Add direct access support for MSR_IA32_SPEC_CTRL Ashok Raj
2018-01-12  1:58   ` Dave Hansen
2018-01-12  3:14     ` Raj, Ashok
2018-01-12  9:51     ` Peter Zijlstra
2018-01-12 10:09       ` David Woodhouse
2018-01-15 13:45         ` Peter Zijlstra
2018-01-15 13:59           ` David Woodhouse
2018-01-15 14:45             ` Peter Zijlstra
2018-01-12  1:32 ` [PATCH 4/5] x86/svm: Direct access to MSR_IA32_SPEC_CTRL Ashok Raj
2018-01-12  7:23   ` David Woodhouse
2018-01-12  9:58     ` Peter Zijlstra
2018-01-12 10:13       ` David Woodhouse
2018-01-12 12:38   ` Paolo Bonzini
2018-01-12 15:14   ` Tom Lendacky
2018-01-12  1:32 ` [PATCH 5/5] x86/feature: Detect the x86 feature Indirect Branch Prediction Barrier Ashok Raj
2018-01-12 10:08   ` Peter Zijlstra
2018-01-12 12:32   ` Borislav Petkov
2018-01-12 12:39     ` Woodhouse, David
2018-01-12 15:21       ` Tom Lendacky [this message]
2018-01-12 15:31   ` Tom Lendacky
2018-01-12 15:36     ` Woodhouse, David
2018-01-12 17:06       ` Tom Lendacky
2018-02-01 21:59 [PATCH v6 0/5] KVM: Expose speculation control feature to guests KarimAllah Ahmed
2018-02-01 21:59 ` KarimAllah Ahmed
2018-02-01 21:59 ` [PATCH v6 1/5] KVM: x86: Update the reverse_cpuid list to include CPUID_7_EDX KarimAllah Ahmed
2018-02-02 17:37   ` Jim Mattson
2018-02-03 22:50   ` [tip:x86/pti] KVM/x86: " tip-bot for KarimAllah Ahmed
2018-02-01 21:59 ` [PATCH v6 2/5] KVM: x86: Add IBPB support KarimAllah Ahmed
2018-02-02 17:49   ` Konrad Rzeszutek Wilk
2018-02-02 18:02     ` David Woodhouse
2018-02-02 18:02       ` David Woodhouse
2018-02-02 19:56       ` Konrad Rzeszutek Wilk
2018-02-02 20:16         ` David Woodhouse
2018-02-02 20:16           ` David Woodhouse
2018-02-02 20:28           ` Konrad Rzeszutek Wilk
2018-02-02 20:31             ` David Woodhouse
2018-02-02 20:31               ` David Woodhouse
2018-02-02 20:52               ` Konrad Rzeszutek Wilk
2018-02-02 20:52             ` Alan Cox
2018-02-05 19:22               ` Paolo Bonzini
2018-02-05 19:24             ` Paolo Bonzini
2018-02-03 22:50   ` [tip:x86/pti] KVM/x86: " tip-bot for Ashok Raj
2018-02-16  3:44   ` [PATCH v6 2/5] KVM: x86: " Jim Mattson
2018-02-16  4:22     ` Andi Kleen
2018-05-03  1:27   ` Wanpeng Li
2018-05-03  9:19     ` Paolo Bonzini
2018-05-03 12:01       ` Wanpeng Li
2018-05-03 12:46       ` Tian, Kevin
2018-02-01 21:59 ` [PATCH v6 3/5] KVM: VMX: Emulate MSR_IA32_ARCH_CAPABILITIES KarimAllah Ahmed
2018-02-02 10:53   ` Darren Kenny
2018-02-02 17:35     ` Jim Mattson
2018-02-02 17:51   ` Konrad Rzeszutek Wilk
2018-02-03 22:51   ` [tip:x86/pti] KVM/VMX: " tip-bot for KarimAllah Ahmed
2018-02-01 21:59 ` [PATCH v6 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL KarimAllah Ahmed
2018-02-02 11:03   ` Darren Kenny
2018-02-02 11:27   ` David Woodhouse
2018-02-02 11:27     ` David Woodhouse
2018-02-02 17:53   ` Konrad Rzeszutek Wilk
2018-02-02 18:05     ` David Woodhouse
2018-02-02 18:19       ` Konrad Rzeszutek Wilk
2018-02-02 17:57   ` Jim Mattson
2018-02-03 22:51   ` [tip:x86/pti] KVM/VMX: " tip-bot for KarimAllah Ahmed
2018-02-01 21:59 ` [PATCH v6 5/5] KVM: SVM: " KarimAllah Ahmed
2018-02-02 11:06   ` Darren Kenny
2018-02-02 18:02   ` Konrad Rzeszutek Wilk

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