Received-SPF: pass (google.com: domain of linux-crypto+bounces-1985-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Mon, 12 Feb 2024 08:27:21 -0800
In-Reply-To: <CABgObfanrHTL429Cr8tcMGqs-Ov+6LWeQbzghvjQiGu9tz0EUA@mail.gmail.com>
Precedence: bulk
Mime-Version: 1.0
References: <20231230172351.574091-1-michael.roth@amd.com> <20231230172351.574091-10-michael.roth@amd.com>
 <CABgObfanrHTL429Cr8tcMGqs-Ov+6LWeQbzghvjQiGu9tz0EUA@mail.gmail.com>
Message-ID: <ZcpG6Ul4_8xAsnuy@google.com>
Subject: Re: [PATCH v11 09/35] KVM: x86: Determine shared/private faults based
 on vm_type
From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>, kvm@vger.kernel.org, linux-coco@lists.linux.dev, 
	linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, 
	linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, 
	jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, 
	vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, 
	dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, 
	peterz@infradead.org, srinivas.pandruvada@linux.intel.com, 
	rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, 
	vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, 
	sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, 
	jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, 
	pankaj.gupta@amd.com, liam.merwick@oracle.com, zhi.a.wang@intel.com
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable

On Mon, Feb 12, 2024, Paolo Bonzini wrote:
> On Sat, Dec 30, 2023 at 6:24=E2=80=AFPM Michael Roth <michael.roth@amd.co=
m> wrote:
> >
> > For KVM_X86_SNP_VM, only the PFERR_GUEST_ENC_MASK flag is needed to
> > determine with an #NPF is due to a private/shared access by the guest.
> > Implement that handling here. Also add handling needed to deal with
> > SNP guests which in some cases will make MMIO accesses with the
> > encryption bit.
> >
> > Signed-off-by: Michael Roth <michael.roth@amd.com>
> > ---
> >  arch/x86/kvm/mmu/mmu.c          | 12 ++++++++++--
> >  arch/x86/kvm/mmu/mmu_internal.h | 20 +++++++++++++++++++-
> >  2 files changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index d3fbfe0686a0..61213f6648a1 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -4331,6 +4331,7 @@ static int kvm_faultin_pfn_private(struct kvm_vcp=
u *vcpu,
> >  static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fa=
ult *fault)
> >  {
> >         struct kvm_memory_slot *slot =3D fault->slot;
> > +       bool private_fault =3D fault->is_private;
>=20
> I think it's nicer to just make the fault !is_private in
> kvm_mmu_do_page_fault().

Yeah.  I'm starting to recall more of this discussion.  This is one of the =
reasons
I suggested/requested stuffing the error code to piggy-back the new SNP bit=
; doing
so allows is_private to be computed from the get-go without needing any ven=
dor
specific hooks.