linux-kernel - Re: [PATCH v2 3/4] x86: Expose SERIALIZE for supported cpuid

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Message-ID: <3EFFDE4B-7844-4BB3-A824-487EE8359376@zytor.com>
Date:   Tue, 14 Jul 2020 16:05:46 -0700
From:   hpa@...or.com
To:     "Zhang, Cathy" <cathy.zhang@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
CC:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        pbonzini@...hat.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de,
        ricardo.neri-calderon@...ux.intel.com, kyung.min.park@...el.com,
        jpoimboe@...hat.com, gregkh@...uxfoundation.org,
        ak@...ux.intel.com, dave.hansen@...el.com, tony.luck@...el.com,
        ravi.v.shankar@...el.com
Subject: Re: [PATCH v2 3/4] x86: Expose SERIALIZE for supported cpuid

On July 14, 2020 3:42:08 PM PDT, "Zhang, Cathy" <cathy.zhang@...el.com> wrote:
>On 7/14/2020 11:00 AM, Sean Christopherson wrote:
>> On Tue, Jul 07, 2020 at 10:16:22AM +0800, Cathy Zhang wrote:
>>> SERIALIZE instruction is supported by intel processors,
>>> like Sapphire Rapids. Expose it in KVM supported cpuid.
>> Providing at least a rough overview of the instruction, e.g. its
>enumeration,
>> usage, fault rules, controls, etc... would be nice.  In isolation,
>the
>> changelog isn't remotely helpful in understanding the correctness of
>the
>> patch.
>Thanks Sean! Add it in the next version.
>>
>>> Signed-off-by: Cathy Zhang <cathy.zhang@...el.com>
>>> ---
>>>   arch/x86/kvm/cpuid.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>>> index 8a294f9..e603aeb 100644
>>> --- a/arch/x86/kvm/cpuid.c
>>> +++ b/arch/x86/kvm/cpuid.c
>>> @@ -341,7 +341,8 @@ void kvm_set_cpu_caps(void)
>>>   	kvm_cpu_cap_mask(CPUID_7_EDX,
>>>   		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
>>>   		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
>>> -		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM)
>>> +		F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) |
>>> +		F(SERIALIZE)
>>>   	);
>>>   
>>>   	/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
>>> -- 
>>> 1.8.3.1
>>>

At least that one is easy: SERIALIZE is architecturally a NOP, but with hard serialization, like CPUID or IRET.

-- 
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