linux-kernel - Re: [PATCHv2 47/59] kvm, x86, mmu: setup MKTME keyID to spte for given PFN

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Message-ID: <a3aee9ea-a3ce-1219-b7ff-5a1b291bffdd@amd.com>
Date:   Tue, 6 Aug 2019 20:26:52 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
CC:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCHv2 47/59] kvm, x86, mmu: setup MKTME keyID to spte for
 given PFN

On 7/31/19 10:08 AM, Kirill A. Shutemov wrote:
> From: Kai Huang <kai.huang@...ux.intel.com>
> 
> Setup keyID to SPTE, which will be eventually programmed to shadow MMU
> or EPT table, according to page's associated keyID, so that guest is
> able to use correct keyID to access guest memory.
> 
> Note current shadow_me_mask doesn't suit MKTME's needs, since for MKTME
> there's no fixed memory encryption mask, but can vary from keyID 1 to
> maximum keyID, therefore shadow_me_mask remains 0 for MKTME.
> 
> Signed-off-by: Kai Huang <kai.huang@...ux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/kvm/mmu.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 8f72526e2f68..b8742e6219f6 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2936,6 +2936,22 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
>  #define SET_SPTE_WRITE_PROTECTED_PT	BIT(0)
>  #define SET_SPTE_NEED_REMOTE_TLB_FLUSH	BIT(1)
>  
> +static u64 get_phys_encryption_mask(kvm_pfn_t pfn)
> +{
> +#ifdef CONFIG_X86_INTEL_MKTME
> +	struct page *page;
> +
> +	if (!pfn_valid(pfn))
> +		return 0;
> +
> +	page = pfn_to_page(pfn);
> +
> +	return ((u64)page_keyid(page)) << mktme_keyid_shift();
> +#else
> +	return shadow_me_mask;
> +#endif
> +}

This patch breaks AMD virtualization (SVM) in general (non-SEV and SEV
guests) when SME is active. Shouldn't this be a run time, vs build time,
check for MKTME being active?

Thanks,
Tom

> +
>  static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  		    unsigned pte_access, int level,
>  		    gfn_t gfn, kvm_pfn_t pfn, bool speculative,
> @@ -2982,7 +2998,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  		pte_access &= ~ACC_WRITE_MASK;
>  
>  	if (!kvm_is_mmio_pfn(pfn))
> -		spte |= shadow_me_mask;
> +		spte |= get_phys_encryption_mask(pfn);
>  
>  	spte |= (u64)pfn << PAGE_SHIFT;
>  
>