From: Isaku Yamahata <isaku.yamahata@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Michael Roth <michael.roth@amd.com>,
Paolo Bonzini <pbonzini@redhat.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, papaluri@amd.com,
Isaku Yamahata <isaku.yamahata@intel.com>,
isaku.yamahata@linux.intel.com, rick.p.edgecombe@intel.com
Subject: Re: [PATCH v15 21/23] KVM: MMU: Disable fast path for private memslots
Date: Fri, 10 May 2024 10:47:00 -0700 [thread overview]
Message-ID: <20240510174700.GB480079@ls.amr.corp.intel.com> (raw)
In-Reply-To: <Zj5ETYPTUo9T4Nuf@google.com>
On Fri, May 10, 2024 at 08:59:09AM -0700,
Sean Christopherson <seanjc@google.com> wrote:
> On Fri, May 10, 2024, Michael Roth wrote:
> > On Fri, May 10, 2024 at 03:50:26PM +0200, Paolo Bonzini wrote:
> > > On Fri, May 10, 2024 at 3:47 PM Sean Christopherson <seanjc@google.com> wrote:
> > > >
> > > > > + * Since software-protected VMs don't have a notion of a shared vs.
> > > > > + * private that's separate from what KVM is tracking, the above
> > > > > + * KVM_EXIT_MEMORY_FAULT condition wouldn't occur, so avoid the
> > > > > + * special handling for that case for now.
> > > >
> > > > Very technically, it can occur if userspace _just_ modified the attributes. And
> > > > as I've said multiple times, at least for now, I want to avoid special casing
> > > > SW-protected VMs unless it is *absolutely* necessary, because their sole purpose
> > > > is to allow testing flows that are impossible to excercise without SNP/TDX hardware.
> > >
> > > Yep, it is not like they have to be optimized.
> >
> > Ok, I thought there were maybe some future plans to use sw-protected VMs
> > to get some added protections from userspace. But even then there'd
> > probably still be extra considerations for how to handle access tracking
> > so white-listing them probably isn't right anyway.
> >
> > I was also partly tempted to take this route because it would cover this
> > TDX patch as well:
> >
> > https://lore.kernel.org/lkml/91c797997b57056224571e22362321a23947172f.1705965635.git.isaku.yamahata@intel.com/
>
> Hmm, I'm pretty sure that patch is trying to fix the exact same issue you are
> fixing, just in a less precise way. S-EPT entries only support RWX=0 and RWX=111b,
> i.e. it should be impossible to have a write-fault to a present S-EPT entry.
>
> And if TDX is running afoul of this code:
>
> if (!fault->present)
> return !kvm_ad_enabled();
>
> then KVM should do the sane thing and require A/D support be enabled for TDX.
>
> And if it's something else entirely, that changelog has some explaining to do.
Yes, it's for KVM_EXIT_MEMORY_FAULT case. Because Secure-EPT has non-present or
all RWX allowed, fast page fault always returns RET_PF_INVALID by
is_shadow_present_pte() check.
I lightly tested the patch at [1] and it works for TDX KVM.
[1] https://github.com/mdroth/linux/commit/39643f9f6da6265d39d633a703c53997985c1208
Just in case for that patch,
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
--
Isaku Yamahata <isaku.yamahata@intel.com>
prev parent reply other threads:[~2024-05-10 17:47 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-01 8:51 [PATCH v15 00/20] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Michael Roth
2024-05-01 8:51 ` [PATCH v15 01/20] Revert "KVM: x86: Add gmem hook for determining max NPT mapping level" Michael Roth
2024-05-01 8:51 ` [PATCH v15 02/20] KVM: x86: Add hook for determining max NPT mapping level Michael Roth
2024-05-02 23:11 ` Isaku Yamahata
2024-05-07 17:48 ` Paolo Bonzini
2024-05-01 8:51 ` [PATCH v15 03/20] KVM: SEV: Select KVM_GENERIC_PRIVATE_MEM when CONFIG_KVM_AMD_SEV=y Michael Roth
2024-05-01 8:51 ` [PATCH v15 04/20] KVM: SEV: Add initial SEV-SNP support Michael Roth
2024-05-01 8:51 ` [PATCH v15 05/20] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command Michael Roth
2024-05-01 8:51 ` [PATCH v15 06/20] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_UPDATE command Michael Roth
2024-05-01 8:51 ` [PATCH v15 07/20] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_FINISH command Michael Roth
2024-05-01 8:51 ` [PATCH v15 08/20] KVM: SEV: Add support to handle GHCB GPA register VMGEXIT Michael Roth
2024-05-01 8:51 ` [PATCH v15 09/20] KVM: SEV: Add support to handle MSR based Page State Change VMGEXIT Michael Roth
2024-05-16 8:28 ` Binbin Wu
2024-05-16 17:23 ` Paolo Bonzini
2024-05-01 8:52 ` [PATCH v15 10/20] KVM: SEV: Add support to handle " Michael Roth
2024-05-01 8:52 ` [PATCH v15 11/20] KVM: SEV: Add support to handle RMP nested page faults Michael Roth
2024-05-01 8:52 ` [PATCH v15 12/20] KVM: SEV: Support SEV-SNP AP Creation NAE event Michael Roth
2024-05-01 8:52 ` [PATCH v15 13/20] KVM: SEV: Implement gmem hook for initializing private pages Michael Roth
2024-05-20 10:16 ` Huang, Kai
2024-05-20 17:35 ` Sean Christopherson
2024-05-01 8:52 ` [PATCH v15 14/20] KVM: SEV: Implement gmem hook for invalidating " Michael Roth
2024-05-01 8:52 ` [PATCH v15 15/20] KVM: x86: Implement hook for determining max NPT mapping level Michael Roth
2024-05-01 8:52 ` [PATCH v15 16/20] KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP Michael Roth
2024-05-01 8:52 ` [PATCH v15 17/20] KVM: SVM: Add module parameter to enable SEV-SNP Michael Roth
2024-05-01 8:52 ` [PATCH v15 18/20] KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event Michael Roth
2024-05-01 8:52 ` [PATCH v15 19/20] KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST " Michael Roth
2024-05-13 23:48 ` Sean Christopherson
2024-05-14 2:51 ` Michael Roth
2024-05-14 14:36 ` Sean Christopherson
2024-05-15 1:25 ` [PATCH] KVM: SEV: Replace KVM_EXIT_VMGEXIT with KVM_EXIT_SNP_REQ_CERTS Michael Roth
2024-05-01 8:52 ` [PATCH v15 20/20] crypto: ccp: Add the SNP_VLEK_LOAD command Michael Roth
2024-05-07 18:04 ` [PATCH v15 00/20] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Paolo Bonzini
2024-05-07 18:14 ` Michael Roth
2024-05-10 2:34 ` Michael Roth
2024-05-10 1:58 ` [PATCH v15 21/23] KVM: MMU: Disable fast path for private memslots Michael Roth
2024-05-10 1:58 ` [PATCH v15 22/23] KVM: SEV: Fix return code interpretation for RMP nested page faults Michael Roth
2024-05-10 13:58 ` Sean Christopherson
2024-05-10 15:36 ` Michael Roth
2024-05-10 16:01 ` Paolo Bonzini
2024-05-10 16:37 ` Michael Roth
2024-05-10 16:59 ` Paolo Bonzini
2024-05-10 17:25 ` Paolo Bonzini
2024-05-14 8:10 ` Borislav Petkov
2024-05-10 1:58 ` [PATCH v15 23/23] KVM: SEV: Fix PSC handling for SMASH/UNSMASH and partial update ops Michael Roth
2024-05-10 17:09 ` Paolo Bonzini
2024-05-10 19:08 ` Michael Roth
2024-05-10 13:47 ` [PATCH v15 21/23] KVM: MMU: Disable fast path for private memslots Sean Christopherson
2024-05-10 13:50 ` Paolo Bonzini
2024-05-10 15:27 ` Michael Roth
2024-05-10 15:59 ` Sean Christopherson
2024-05-10 17:47 ` Isaku Yamahata [this message]
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