linux-kernel - Re: [PATCH 38/61] KVM: x86: Introduce kvm_cpu

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Date:   Tue, 25 Feb 2020 00:20:03 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 38/61] KVM: x86: Introduce kvm_cpu_caps to replace runtime CPUID masking

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> On Mon, Feb 24, 2020 at 05:32:54PM +0100, Vitaly Kuznetsov wrote:
>> Sean Christopherson <sean.j.christopherson@...el.com> writes:
>> 

...

>
>> > +
>> > +	BUILD_BUG_ON(sizeof(kvm_cpu_caps) >
>> > +		     sizeof(boot_cpu_data.x86_capability));
>> > +
>> > +	memcpy(&kvm_cpu_caps, &boot_cpu_data.x86_capability,
>> > +	       sizeof(kvm_cpu_caps));
>> > +
>> > +	kvm_cpu_cap_mask(CPUID_1_EDX,
>> > +		F(FPU) | F(VME) | F(DE) | F(PSE) |
>> > +		F(TSC) | F(MSR) | F(PAE) | F(MCE) |
>> > +		F(CX8) | F(APIC) | 0 /* Reserved */ | F(SEP) |
>> > +		F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
>> > +		F(PAT) | F(PSE36) | 0 /* PSN */ | F(CLFLUSH) |
>> > +		0 /* Reserved, DS, ACPI */ | F(MMX) |
>> > +		F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) |
>> > +		0 /* HTT, TM, Reserved, PBE */
>> > +	);
>> > +
>> > +	kvm_cpu_cap_mask(CPUID_8000_0001_EDX,
>> > +		F(FPU) | F(VME) | F(DE) | F(PSE) |
>> > +		F(TSC) | F(MSR) | F(PAE) | F(MCE) |
>> > +		F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) |
>> > +		F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
>> > +		F(PAT) | F(PSE36) | 0 /* Reserved */ |
>> > +		f_nx | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
>> > +		F(FXSR) | F(FXSR_OPT) | f_gbpages | F(RDTSCP) |
>> > +		0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW)
>> > +	);
>> > +
>> > +	kvm_cpu_cap_mask(CPUID_1_ECX,
>> > +		/* NOTE: MONITOR (and MWAIT) are emulated as NOP,
>> > +		 * but *not* advertised to guests via CPUID ! */
>> > +		F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
>> > +		0 /* DS-CPL, VMX, SMX, EST */ |
>> > +		0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
>> > +		F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ |
>> > +		F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
>> > +		F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
>> > +		0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
>> > +		F(F16C) | F(RDRAND)
>> > +	);
>> 
>> I would suggest we order things by CPUID_NUM here, i.e.
>> 
>> CPUID_1_ECX
>> CPUID_1_EDX
>> CPUID_7_1_EAX
>> CPUID_7_0_EBX
>> CPUID_7_ECX
>> CPUID_7_EDX
>> CPUID_D_1_EAX
>> ...
>
> Hmm, generally speaking I agree, but I didn't want to change the ordering
> in this patch when moving the code.  Throw a patch on top?  Leave as is?
> Something else?

My line of thought was: it's not a mechanical "s,const u32
xxx_x86_features =,kvm_cpu_cap_mask...," change, things get moved from
do_cpuid_7_mask() and __do_cpuid_func() so we may as well re-order them,
reviewing-wise it's more or less the same. But honestly, this is very
minor, feel free to leave as-is.

-- 
Vitaly