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

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Message-ID: <20190807142850.mjp4ctqc7wttpser@box>
Date:   Wed, 7 Aug 2019 17:28:50 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     "Lendacky, Thomas" <Thomas.Lendacky@....com>
Cc:     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>,
        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 Tue, Aug 06, 2019 at 08:26:52PM +0000, Lendacky, Thomas wrote:
> 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, I've missed this.

This fixup should help:

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 00d17bdfec0f..54931acf260e 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2947,18 +2947,17 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
 
 static u64 get_phys_encryption_mask(kvm_pfn_t pfn)
 {
-#ifdef CONFIG_X86_INTEL_MKTME
 	struct page *page;
 
+	if (!mktme_enabled())
+		return shadow_me_mask;
+
 	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
 }
 
 static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
-- 
 Kirill A. Shutemov