linux-kernel - Re: [PATCH 44/61] KVM: x86: Use KVM cpu caps to track UMIP emulation

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Date:   Mon, 24 Feb 2020 23:13:37 +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 44/61] KVM: x86: Use KVM cpu caps to track UMIP emulation

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

> Set UMIP in kvm_cpu_caps when it is emulated by VMX, even though the
> bit will be effectively be dropped 

Redundant 'be'

> by do_host_cpuid().  This allows checking for UMIP emulation via
> kvm_cpu_caps instead of a dedicated kvm_x86_ops callback.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/svm.c              | 6 ------
>  arch/x86/kvm/vmx/vmx.c          | 8 +++++++-
>  arch/x86/kvm/x86.c              | 2 +-
>  4 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index dd690fb5ceca..113b138a0347 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1163,7 +1163,6 @@ struct kvm_x86_ops {
>  	void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
>  		enum exit_fastpath_completion *exit_fastpath);
>  
> -	bool (*umip_emulated)(void);
>  	bool (*pt_supported)(void);
>  
>  	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index defb2c0dbf8a..e1ed5726964c 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6079,11 +6079,6 @@ static bool svm_rdtscp_supported(void)
>  	return boot_cpu_has(X86_FEATURE_RDTSCP);
>  }
>  
> -static bool svm_umip_emulated(void)
> -{
> -	return false;
> -}
> -
>  static bool svm_pt_supported(void)
>  {
>  	return false;
> @@ -7449,7 +7444,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>  	.cpuid_update = svm_cpuid_update,
>  
>  	.rdtscp_supported = svm_rdtscp_supported,
> -	.umip_emulated = svm_umip_emulated,
>  	.pt_supported = svm_pt_supported,
>  
>  	.set_supported_cpuid = svm_set_supported_cpuid,
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index cecf59225136..cd5a624610c9 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7103,6 +7103,10 @@ static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  {
>  	switch (entry->function) {
>  	case 0x7:
> +		/*
> +		 * UMIP needs to be manually set even though vmx_set_cpu_caps()
> +		 * also sets UMIP since do_host_cpuid() will drop it.
> +		 */
>  		if (vmx_umip_emulated())
>  			cpuid_entry_set(entry, X86_FEATURE_UMIP);
>  		break;
> @@ -7129,6 +7133,9 @@ static __init void vmx_set_cpu_caps(void)
>  	if (enable_ept && boot_cpu_has(X86_FEATURE_OSPKE))
>  		kvm_cpu_cap_check_and_set(X86_FEATURE_PKU);
>  
> +	if (vmx_umip_emulated())
> +		kvm_cpu_cap_set(X86_FEATURE_UMIP);
> +
>  	/* CPUID 0xD.1 */
>  	if (!vmx_xsaves_supported())
>  		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
> @@ -7888,7 +7895,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>  
>  	.check_intercept = vmx_check_intercept,
>  	.handle_exit_irqoff = vmx_handle_exit_irqoff,
> -	.umip_emulated = vmx_umip_emulated,
>  	.pt_supported = vmx_pt_supported,
>  
>  	.request_immediate_exit = vmx_request_immediate_exit,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cb40737187a1..a6d5f22c7ef6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -915,7 +915,7 @@ static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
>  	if (kvm_cpu_cap_has(X86_FEATURE_LA57))
>  		reserved_bits &= ~X86_CR4_LA57;
>  
> -	if (kvm_x86_ops->umip_emulated())
> +	if (kvm_cpu_cap_has(X86_FEATURE_UMIP))
>  		reserved_bits &= ~X86_CR4_UMIP;
>  
>  	return reserved_bits;

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly