linux-kernel - Re: [PATCH v2 3/3] KVM: SVM: Add support for MPK feature on AMD

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Date:   Fri, 8 May 2020 14:55:54 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Babu Moger <babu.moger@....com>
Cc:     corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
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Subject: Re: [PATCH v2 3/3] KVM: SVM: Add support for MPK feature on AMD

On Fri, May 08, 2020 at 04:10:03PM -0500, Babu Moger wrote:
> The Memory Protection Key (MPK) feature provides a way for applications
> to impose page-based data access protections (read/write, read-only or
> no access), without requiring modification of page tables and subsequent
> TLB invalidations when the application changes protection domains.
> 
> This feature is already available in Intel platforms. Now enable the
> feature on AMD platforms.
> 
> AMD documentation for MPK feature is available at "AMD64 Architecture
> Programmer’s Manual Volume 2: System Programming, Pub. 24593 Rev. 3.34,
> Section 5.6.6 Memory Protection Keys (MPK) Bit". Documentation can be
> obtained at the link below.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kvm/svm/svm.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 2f379bacbb26..37fb41ad9149 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -818,6 +818,10 @@ static __init void svm_set_cpu_caps(void)
>  	if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) ||
>  	    boot_cpu_has(X86_FEATURE_AMD_SSBD))
>  		kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD);
> +
> +	/* PKU is not yet implemented for shadow paging. */
> +	if (npt_enabled && boot_cpu_has(X86_FEATURE_OSPKE))
> +		kvm_cpu_cap_check_and_set(X86_FEATURE_PKU);

This can actually be done in common code as well since both VMX and SVM
call kvm_set_cpu_caps() after kvm_configure_mmu(), i.e. key off of
tdp_enabled.

>  }
>  
>  static __init int svm_hardware_setup(void)
>