linux-kernel - Re: [RFC 10/16] KVM: x86: Enabled protected memory extension

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Date:   Tue, 26 May 2020 09:16:09 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC 10/16] KVM: x86: Enabled protected memory extension

On Fri, May 22, 2020 at 03:52:08PM +0300, Kirill A. Shutemov wrote:
> Wire up hypercalls for the feature and define VM_KVM_PROTECTED.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/Kconfig     | 1 +
>  arch/x86/kvm/cpuid.c | 3 +++
>  arch/x86/kvm/x86.c   | 9 +++++++++
>  include/linux/mm.h   | 4 ++++
>  4 files changed, 17 insertions(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 58dd44a1b92f..420e3947f0c6 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -801,6 +801,7 @@ config KVM_GUEST
>  	select ARCH_CPUIDLE_HALTPOLL
>  	select X86_MEM_ENCRYPT_COMMON
>  	select SWIOTLB
> +	select ARCH_USES_HIGH_VMA_FLAGS
>  	default y
>  	---help---
>  	  This option enables various optimizations for running under the KVM
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 901cd1fdecd9..94cc5e45467e 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -714,6 +714,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>  			     (1 << KVM_FEATURE_POLL_CONTROL) |
>  			     (1 << KVM_FEATURE_PV_SCHED_YIELD);
>  
> +		if (VM_KVM_PROTECTED)
> +			entry->eax |=(1 << KVM_FEATURE_MEM_PROTECTED);
> +
>  		if (sched_info_on())
>  			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c17e6eb9ad43..acba0ac07f61 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7598,6 +7598,15 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
>  		kvm_sched_yield(vcpu->kvm, a0);
>  		ret = 0;
>  		break;
> +	case KVM_HC_ENABLE_MEM_PROTECTED:
> +		ret = kvm_protect_all_memory(vcpu->kvm);
> +		break;
> +	case KVM_HC_MEM_SHARE:
> +		ret = kvm_protect_memory(vcpu->kvm, a0, a1, false);
> +		break;
> +	case KVM_HC_MEM_UNSHARE:
> +		ret = kvm_protect_memory(vcpu->kvm, a0, a1, true);
> +		break;
>  	default:
>  		ret = -KVM_ENOSYS;
>  		break;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 4f7195365cc0..6eb771c14968 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -329,7 +329,11 @@ extern unsigned int kobjsize(const void *objp);
>  # define VM_MAPPED_COPY	VM_ARCH_1	/* T if mapped copy of data (nommu mmap) */
>  #endif
>  
> +#if defined(CONFIG_X86_64) && defined(CONFIG_KVM)

This would be better spelled as ARCH_WANTS_PROTECTED_MEMORY, IMHO.

> +#define VM_KVM_PROTECTED VM_HIGH_ARCH_4

Maybe this should be VM_HIGH_ARCH_5 so that powerpc could enable this
feature eventually?

> +#else
>  #define VM_KVM_PROTECTED 0
> +#endif
>  
>  #ifndef VM_GROWSUP
>  # define VM_GROWSUP	VM_NONE
> -- 
> 2.26.2
> 
> 

-- 
Sincerely yours,
Mike.