From: Borislav Petkov <bp@alien8.de>
To: Michael Roth <michael.roth@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, linux-efi@vger.kernel.org,
platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Andi Kleen <ak@linux.intel.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
tony.luck@intel.com, marcorr@google.com,
sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v6 08/42] x86/sev-es: initialize sev_status/features within #VC handler
Date: Thu, 21 Oct 2021 16:48:16 +0200 [thread overview]
Message-ID: <YXF9sCbPDsLwlm42@zn.tnic> (raw)
In-Reply-To: <20211020161023.hzbj53ehmzjrt4xd@amd.com>
On Wed, Oct 20, 2021 at 11:10:23AM -0500, Michael Roth wrote:
> At which point we then switch to using the CPUID table? But at that
> point all the previous CPUID checks, both SEV-related/non-SEV-related,
> are now possibly not consistent with what's in the CPUID table. Do we
> then revalidate?
Well, that's a tough question. That's basically the same question as,
does Linux support heterogeneous cores and can it handle hardware
features which get enabled after boot. The perfect example is, late
microcode loading which changes CPUID bits and adds new functionality.
And the answer to that is, well, hard. You need to decide this on a
case-by-case basis.
But isn't it that the SNP CPUID page will be parsed early enough anyway
so that kernel proper will see only SNP CPUID info and init properly
using that?
> Even a non-malicious hypervisor might provide inconsistent values
> between the two sources due to bugs, or SNP validation suppressing
> certain feature bits that hypervisor otherwise exposes, etc.
There's also migration, lemme point to a very recent example:
https://lore.kernel.org/r/20211021104744.24126-1-jane.malalane@citrix.com
which is exactly what you say - a non-malicious HV taking care of its
migration pool. So how do you handle that?
> Now all the code after sme_enable() can potentially take unexpected
> execution paths, where post-sme_enable() code makes assumptions about
> pre-sme_enable() checks that may no longer hold true.
So as I said above, if you parse SNP CPUID page early enough, you don't
have to worry about feature rediscovery. Early enough means, before
identify_boot_cpu().
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-10-21 14:48 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 18:04 [PATCH v6 00/42] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 01/42] x86/mm: Extend cc_attr to include AMD SEV-SNP Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 02/42] x86/sev: Shorten GHCB terminate macro names Brijesh Singh
2021-10-11 13:15 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 03/42] x86/sev: Get rid of excessive use of defines Brijesh Singh
2021-10-11 8:48 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 04/42] x86/head64: Carve out the guest encryption postprocessing into a helper Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 05/42] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 06/42] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 07/42] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-10-13 14:02 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 08/42] x86/sev-es: initialize sev_status/features within #VC handler Brijesh Singh
2021-10-18 14:29 ` Borislav Petkov
2021-10-18 18:40 ` Michael Roth
2021-10-18 19:18 ` Borislav Petkov
2021-10-20 16:10 ` Michael Roth
2021-10-20 18:01 ` Borislav Petkov
2021-10-21 0:35 ` Michael Roth
2021-10-21 14:28 ` Borislav Petkov
2021-10-20 18:08 ` Borislav Petkov
2021-10-21 2:05 ` Michael Roth
2021-10-21 14:39 ` Borislav Petkov
2021-10-21 23:00 ` Michael Roth
2021-10-21 14:48 ` Borislav Petkov [this message]
2021-10-21 15:56 ` Dr. David Alan Gilbert
2021-10-21 16:55 ` Borislav Petkov
2021-10-21 17:12 ` Dr. David Alan Gilbert
2021-10-21 17:37 ` Borislav Petkov
2021-10-21 17:47 ` Dr. David Alan Gilbert
2021-10-21 18:46 ` Borislav Petkov
2021-10-21 21:34 ` Michael Roth
2021-10-21 14:51 ` Borislav Petkov
2021-10-21 20:41 ` Michael Roth
2021-10-25 11:04 ` Borislav Petkov
2021-10-25 16:35 ` Michael Roth
2021-10-27 11:17 ` Borislav Petkov
2021-10-27 15:13 ` Michael Roth
2021-10-08 18:04 ` [PATCH v6 09/42] x86/sev: Check SEV-SNP features support Brijesh Singh
2021-10-19 14:47 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 10/42] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 11/42] x86/sev: Check the vmpl level Brijesh Singh
2021-10-28 15:07 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 12/42] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 13/42] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-11-02 16:33 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 14/42] x86/sev: " Brijesh Singh
2021-11-02 16:53 ` Borislav Petkov
2021-11-02 18:24 ` Brijesh Singh
2021-11-02 18:44 ` Borislav Petkov
2021-11-03 20:10 ` Brijesh Singh
2021-11-04 13:58 ` Borislav Petkov
2021-11-04 15:26 ` Brijesh Singh
2021-11-04 16:03 ` Boris Petkov
2021-10-08 18:04 ` [PATCH v6 15/42] x86/sev: Remove do_early_exception() forward declarations Brijesh Singh
2021-11-02 16:54 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 16/42] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 17/42] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 18/42] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 19/42] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-11-09 19:34 ` Borislav Petkov
2021-11-10 14:21 ` Brijesh Singh
2021-11-10 18:43 ` Borislav Petkov
2021-11-11 14:49 ` Tom Lendacky
2021-11-11 16:01 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 20/42] KVM: SVM: Define sev_features and vmpl field in the VMSA Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 21/42] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 22/42] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 23/42] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 24/42] x86/sev: Use SEV-SNP AP creation to start secondary CPUs Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 25/42] x86/head: re-enable stack protection for 32/64-bit builds Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 26/42] x86/sev: move MSR-based VMGEXITs for CPUID to helper Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 27/42] KVM: x86: move lookup of indexed CPUID leafs " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 28/42] x86/compressed/acpi: move EFI system table lookup " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 29/42] x86/compressed/acpi: move EFI config " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 30/42] x86/compressed/acpi: move EFI vendor " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 31/42] x86/boot: Add Confidential Computing type to setup_data Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 32/42] x86/compressed/64: add support for SEV-SNP CPUID table in #VC handlers Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 33/42] boot/compressed/64: use firmware-validated CPUID for SEV-SNP guests Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 34/42] x86/boot: add a pointer to Confidential Computing blob in bootparams Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 35/42] x86/compressed/64: store Confidential Computing blob address " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 36/42] x86/compressed/64: add identity mapping for Confidential Computing blob Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 37/42] x86/sev: use firmware-validated CPUID for SEV-SNP guests Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 38/42] x86/sev: Provide support for SNP guest request NAEs Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 39/42] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 40/42] virt: Add SEV-SNP guest driver Brijesh Singh
2021-10-10 17:51 ` Dov Murik
2021-10-13 11:37 ` Brijesh Singh
2021-10-20 21:33 ` Peter Gonda
2021-10-27 16:07 ` Brijesh Singh
2021-10-27 20:10 ` Peter Gonda
2021-10-27 20:47 ` Brijesh Singh
2021-10-27 21:05 ` Peter Gonda
2021-10-27 21:12 ` Brijesh Singh
2021-10-27 21:15 ` Peter Gonda
2021-10-08 18:04 ` [PATCH v6 41/42] virt: sevguest: Add support to derive key Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 42/42] virt: sevguest: Add support to get extended report Brijesh Singh
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