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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Robert Hoo <robert.hu@linux.intel.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, xiaoyao.li@intel.com,
	vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org, robert.hu@intel.com
Subject: Re: [RFC PATCH 1/9] KVM:x86: Abstract sub functions from kvm_update_cpuid_runtime() and kvm_vcpu_after_set_cpuid()
Date: Mon, 28 Sep 2020 21:56:50 -0700
Message-ID: <20200929045649.GM31514@linux.intel.com> (raw)
In-Reply-To: <1596163347-18574-2-git-send-email-robert.hu@linux.intel.com>

I think you want "extract", not "abstract".


On Fri, Jul 31, 2020 at 10:42:19AM +0800, Robert Hoo wrote:
> Add below functions, whose aggregation equals kvm_update_cpuid_runtime() and
> kvm_vcpu_after_set_cpuid().
> 
> void kvm_osxsave_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> void kvm_pke_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> void kvm_apic_base_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> void kvm_mwait_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> void kvm_xcr0_update_cpuid(struct kvm_vcpu *vcpu)
> static void kvm_pv_unhalt_update_cpuid(struct kvm_vcpu *vcpu)
> static void kvm_update_maxphyaddr(struct kvm_vcpu *vcpu)
> static void kvm_update_lapic_timer_mode(struct kvm_vcpu *vcpu)
> 
> And, for some among the above, avoid double check set or clear inside function
> body, but provided by caller.
> 
> Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
> ---
>  arch/x86/kvm/cpuid.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/cpuid.h |  6 ++++
>  2 files changed, 105 insertions(+)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 7d92854..efa7182 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -73,6 +73,105 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> +void kvm_osxsave_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> +{
> +	struct kvm_cpuid_entry2 *best;

I vote that we opportunistically move away from the "best" terminology.  Either
there's a matching entry or there's not.  Using "e" would probably shave a few
lines of code.

> +
> +	best = kvm_find_cpuid_entry(vcpu, 1, 0);
> +
> +	if (best && boot_cpu_has(X86_FEATURE_XSAVE)) {

Braces not needed. We should also check boot_cpu_has() first, it's constant
time and maybe even in the cache, whereas finding CPUID entries is linear
time and outright slow.

Actually, can you add a helper to handle this?  With tht boot_cpu_has() check
outside of the helper?  That'll allow the helper to be used for more features,
and will force checking boot_cpu_has() first.  Hmm, and not all of the callers
will need the boot_cpu_has() check, e.g. toggling PKE from kvm_set_cr4()
doesn't need to be guarded because KVM disallows setting PKE if it's not
supported by the host.

static inline void guest_cpuid_change(struct kvm_vcpu *vcpu, u32 function,
				      u32 index, unsigned int feature, bool set)
{
	struct kvm_cpuid_entry2 *e =  kvm_find_cpuid_entry(vcpu, function, index);

	if (e)
		cpuid_entry_change(best, X86_FEATURE_OSXSAVE, set);
}

> +		cpuid_entry_change(best, X86_FEATURE_OSXSAVE, set);
> +	}
> +}
> +
> +void kvm_pke_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> +{
> +	struct kvm_cpuid_entry2 *best;
> +
> +	best = kvm_find_cpuid_entry(vcpu, 7, 0);
> +
> +	if (best && boot_cpu_has(X86_FEATURE_PKU)) {
> +		cpuid_entry_change(best, X86_FEATURE_OSPKE, set);
> +	}
> +}
> +
> +void kvm_xcr0_update_cpuid(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_cpuid_entry2 *best;a
> +
> +	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
> +	if (!best) {
> +		vcpu->arch.guest_supported_xcr0 = 0;
> +	} else {
> +		vcpu->arch.guest_supported_xcr0 =
> +			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
> +		best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
> +	}
> +
> +	best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
> +	if (!best)
> +		return;
> +	if (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> +				cpuid_entry_has(best, X86_FEATURE_XSAVEC))

Indentation should be aligned, e.g.

	if (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
	    cpuid_entry_has(best, X86_FEATURE_XSAVEC))


> +		best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
> +}
> +
> +static void kvm_pv_unhalt_update_cpuid(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_cpuid_entry2 *best;
> +
> +	best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
> +	if (kvm_hlt_in_guest(vcpu->kvm) && best &&
> +					(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
> +		best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
> +}
> +
> +void kvm_mwait_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> +{
> +	struct kvm_cpuid_entry2 *best;
> +
> +	best = kvm_find_cpuid_entry(vcpu, 0x1, 0);
> +	if (best)
> +		cpuid_entry_change(best, X86_FEATURE_MWAIT, set);
> +}
> +
> +static void kvm_update_maxphyaddr(struct kvm_vcpu *vcpu)
> +{
> +
> +	/* Note, maxphyaddr must be updated before tdp_level. */
> +	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> +	vcpu->arch.tdp_level = kvm_x86_ops.get_tdp_level(vcpu);
> +	kvm_mmu_reset_context(vcpu);
> +}
> +
> +void kvm_apic_base_update_cpuid(struct kvm_vcpu *vcpu, bool set)
> +{
> +	struct kvm_cpuid_entry2 *best;
> +
> +	best = kvm_find_cpuid_entry(vcpu, 1, 0);
> +	if (!best)
> +		return;
> +
> +	cpuid_entry_change(best, X86_FEATURE_APIC, set);
> +}
> +
> +static void kvm_update_lapic_timer_mode(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_cpuid_entry2 *best;
> +	struct kvm_lapic *apic = vcpu->arch.apic;
> +
> +	best = kvm_find_cpuid_entry(vcpu, 1, 0);
> +	if (!best)
> +		return;
> +
> +	if (apic) {

Check apic before the lookup.

> +		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
> +			apic->lapic_timer.timer_mode_mask = 3 << 17;
> +		else
> +			apic->lapic_timer.timer_mode_mask = 1 << 17;
> +	}
> +}
> +
>  void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 3a923ae..7eabb44 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -9,6 +9,12 @@
>  extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
>  void kvm_set_cpu_caps(void);
>  
> +void kvm_osxsave_update_cpuid(struct kvm_vcpu *vcpu, bool set);
> +void kvm_pke_update_cpuid(struct kvm_vcpu *vcpu, bool set);
> +void kvm_apic_base_update_cpuid(struct kvm_vcpu *vcpu, bool set);
> +void kvm_mwait_update_cpuid(struct kvm_vcpu *vcpu, bool set);
> +void kvm_xcr0_update_cpuid(struct kvm_vcpu *vcpu);
> +
>  void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu);
>  struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
>  					      u32 function, u32 index);
> -- 
> 1.8.3.1
> 

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31  2:42 [RFC PATCH 0/9] Split kvm_update_cpuid_runtime() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 1/9] KVM:x86: Abstract sub functions from kvm_update_cpuid_runtime() and kvm_vcpu_after_set_cpuid() Robert Hoo
2020-09-29  4:56   ` Sean Christopherson [this message]
2020-10-20  5:38     ` Robert Hoo
2020-10-20 16:44       ` Sean Christopherson
2020-09-29  4:58   ` Sean Christopherson
2020-07-31  2:42 ` [RFC PATCH 2/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_apic_base_update_cpuid() in kvm_lapic_set_base() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 3/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_xcr0_update_cpuid() in __kvm_set_xcr() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 4/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_{osxsave,pke}_update_cpuid() in kvm_set_cr4() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 5/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_mwait_update_cpuid() in kvm_set_msr_common() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 6/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_{osxsave,pke}_update_cpuid() in enter_smm() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 7/9] KVM:x86: Substitute kvm_update_cpuid_runtime() with kvm_{osxsave,pke}_update_cpuid() in __set_sregs() Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 8/9] KVM:x86: Substitute kvm_vcpu_after_set_cpuid() with abstracted functions Robert Hoo
2020-07-31  2:42 ` [RFC PATCH 9/9] KVM:x86: Remove kvm_update_cpuid_runtime() Robert Hoo

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