linux-kernel - Re: [PATCH v3 16/18] x86/virt: KVM: Move "disable SVM" helper into KVM SVM

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Message-ID: <b68a28170c774a51ea108c15dd124b6754d6128e.camel@intel.com>
Date:   Mon, 22 May 2023 23:26:13 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gao, Chao" <chao.gao@...el.com>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>
Subject: Re: [PATCH v3 16/18] x86/virt: KVM: Move "disable SVM" helper into
 KVM SVM

On Fri, 2023-05-12 at 16:50 -0700, Sean Christopherson wrote:
> Move cpu_svm_disable() into KVM proper now that all hardware
> virtualization management is routed through KVM.  Remove the now-empty
> virtext.h.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Kai Huang <kai.huang@...el.com>

> ---
>  arch/x86/include/asm/virtext.h | 50 ----------------------------------
>  arch/x86/kvm/svm/svm.c         | 28 +++++++++++++++++--
>  2 files changed, 25 insertions(+), 53 deletions(-)
>  delete mode 100644 arch/x86/include/asm/virtext.h
> 
> diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
> deleted file mode 100644
> index 632575e257d8..000000000000
> --- a/arch/x86/include/asm/virtext.h
> +++ /dev/null
> @@ -1,50 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0-only */
> -/* CPU virtualization extensions handling
> - *
> - * This should carry the code for handling CPU virtualization extensions
> - * that needs to live in the kernel core.
> - *
> - * Author: Eduardo Habkost <ehabkost@...hat.com>
> - *
> - * Copyright (C) 2008, Red Hat Inc.
> - *
> - * Contains code from KVM, Copyright (C) 2006 Qumranet, Inc.
> - */
> -#ifndef _ASM_X86_VIRTEX_H
> -#define _ASM_X86_VIRTEX_H
> -
> -#include <asm/processor.h>
> -
> -#include <asm/vmx.h>
> -#include <asm/svm.h>
> -#include <asm/tlbflush.h>
> -
> -/*
> - * SVM functions:
> - */
> -/** Disable SVM on the current CPU
> - */
> -static inline void cpu_svm_disable(void)
> -{
> -	uint64_t efer;
> -
> -	wrmsrl(MSR_VM_HSAVE_PA, 0);
> -	rdmsrl(MSR_EFER, efer);
> -	if (efer & EFER_SVME) {
> -		/*
> -		 * Force GIF=1 prior to disabling SVM to ensure INIT and NMI
> -		 * aren't blocked, e.g. if a fatal error occurred between CLGI
> -		 * and STGI.  Note, STGI may #UD if SVM is disabled from NMI
> -		 * context between reading EFER and executing STGI.  In that
> -		 * case, GIF must already be set, otherwise the NMI would have
> -		 * been blocked, so just eat the fault.
> -		 */
> -		asm_volatile_goto("1: stgi\n\t"
> -				  _ASM_EXTABLE(1b, %l[fault])
> -				  ::: "memory" : fault);
> -fault:
> -		wrmsrl(MSR_EFER, efer & ~EFER_SVME);
> -	}
> -}
> -
> -#endif /* _ASM_X86_VIRTEX_H */
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index cf5f3880751b..2cc195d95d32 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -41,7 +41,6 @@
>  #include <asm/reboot.h>
>  #include <asm/fpu/api.h>
>  
> -#include <asm/virtext.h>
>  #include "trace.h"
>  
>  #include "svm.h"
> @@ -587,9 +586,32 @@ void __svm_write_tsc_multiplier(u64 multiplier)
>  	preempt_enable();
>  }
>  
> +static inline void kvm_cpu_svm_disable(void)
> +{
> +	uint64_t efer;
> +
> +	wrmsrl(MSR_VM_HSAVE_PA, 0);
> +	rdmsrl(MSR_EFER, efer);
> +	if (efer & EFER_SVME) {
> +		/*
> +		 * Force GIF=1 prior to disabling SVM to ensure INIT and NMI
> +		 * aren't blocked, e.g. if a fatal error occurred between CLGI
> +		 * and STGI.  Note, STGI may #UD if SVM is disabled from NMI
> +		 * context between reading EFER and executing STGI.  In that
> +		 * case, GIF must already be set, otherwise the NMI would have
> +		 * been blocked, so just eat the fault.
> +		 */
> +		asm_volatile_goto("1: stgi\n\t"
> +				  _ASM_EXTABLE(1b, %l[fault])
> +				  ::: "memory" : fault);
> +fault:
> +		wrmsrl(MSR_EFER, efer & ~EFER_SVME);
> +	}
> +}
> +
>  static void svm_emergency_disable(void)
>  {
> -	cpu_svm_disable();
> +	kvm_cpu_svm_disable();
>  }
>  
>  static void svm_hardware_disable(void)
> @@ -598,7 +620,7 @@ static void svm_hardware_disable(void)
>  	if (tsc_scaling)
>  		__svm_write_tsc_multiplier(SVM_TSC_RATIO_DEFAULT);
>  
> -	cpu_svm_disable();
> +	kvm_cpu_svm_disable();
>  
>  	amd_pmu_disable_virt();
>  }
> -- 
> 2.40.1.606.ga4b1b128d6-goog
>