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From: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Michael Roth <michael.roth@amd.com>,
	x86@kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev,
	linux-mm@kvack.org, linux-crypto@vger.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, pbonzini@redhat.com,
	seanjc@google.com, 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,
	tobin@ibm.com, 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, Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: [PATCH v1 04/26] x86/sev: Add the host SEV-SNP initialization support
Date: Tue, 9 Jan 2024 12:56:17 +0100	[thread overview]
Message-ID: <b5b57b60-1573-44f4-8161-e2249eb6f9b6@linux.microsoft.com> (raw)
In-Reply-To: <20240108170418.GDZZwrEiIaGuMpV0B0@fat_crate.local>

On 08/01/2024 18:04, Borislav Petkov wrote:
> On Mon, Jan 08, 2024 at 05:49:01PM +0100, Jeremi Piotrowski wrote:
>> What I wrote: "allow for the kernel to allocate the rmptable".
> 
> What?!
> 
> "15.36.5 Hypervisor RMP Management
> 
> ...
> 
> Because the RMP is initialized by the AMD-SP to prevent direct access to
> the RMP, the hypervisor must use the RMPUPDATE instruction to alter the
> entries of the RMP. RMPUPDATE allows the hypervisor to alter the
> Guest_Physical_Address, Assigned, Page_Size, Immutable, and ASID fields
> of an RMP entry."
>> What you want is something that you should keep far and away from the
> upstream kernel.
>

Can we please not assume I am acting in bad faith. I am explicitly trying to
integrate nicely with AMD's KVM SNP host patches to cover an additional usecase
and get something upstreamable.

Let's separate RMP allocation from who (and how) maintains the entries.

"""
15.36.4 Initializing the RMP
...
Software must program RMP_BASE and RMP_END identically for each core in the
system and before enabling SEV-SNP globally.
"""

KVM expects UEFI to do this, Hyper-V does the allocation itself (on bare-metal).
Both are valid. Afaik it is the SNP_INIT command that hands over control of the
RMP from software to AMD-SP.

When it comes to "who and how maintains the rmp" - that is of course the AMD-SP
and hypervisor issues RMPUPDATE instructions. The paragraph you cite talks about
the physical RMP and AMD-SP - not virtualized SNP (aka "SNP-host VM"/nested SNP).
AMD specified an MSR-based RMPUPDATE for us for that usecase (15.36.19 SEV-SNP
Instruction Virtualization). The RMP inside the SNP-host VM is not related to
the physical RMP and is an entirely software based construct.

The RMP in nested SNP is only used for kernel bookkeeping and so its allocation
is optional. KVM could do without reading the RMP directly altogether (by tracking
the assigned bit somewhere) but that would be a design change and I'd rather see
the KVM SNP host patches merged in their current shape. Which is why the patch
I linked allocates a (shadow) RMP from the kernel.

I would very much appreciate if we would not prevent that usecase from working -
that's why I've been reviewing and testing multiple revisions of these patches
and providing feedback all along.

  reply	other threads:[~2024-01-09 11:56 UTC|newest]

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-30 16:19 [PATCH v1 00/26] Add AMD Secure Nested Paging (SEV-SNP) Initialization Support Michael Roth
2023-12-30 16:19 ` [PATCH v1 01/26] x86/cpufeatures: Add SEV-SNP CPU feature Michael Roth
2023-12-31 11:50   ` Borislav Petkov
2023-12-31 16:44     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 02/26] x86/speculation: Do not enable Automatic IBRS if SEV SNP is enabled Michael Roth
2023-12-30 16:19 ` [PATCH v1 03/26] iommu/amd: Don't rely on external callers to enable IOMMU SNP support Michael Roth
2024-01-04 10:30   ` Borislav Petkov
2024-01-04 10:58   ` Joerg Roedel
2023-12-30 16:19 ` [PATCH v1 04/26] x86/sev: Add the host SEV-SNP initialization support Michael Roth
2024-01-04 11:05   ` Jeremi Piotrowski
2024-01-05 16:09     ` Borislav Petkov
2024-01-05 16:21       ` Borislav Petkov
2024-01-08 16:49         ` Jeremi Piotrowski
2024-01-08 17:04           ` Borislav Petkov
2024-01-09 11:56             ` Jeremi Piotrowski [this message]
2024-01-09 12:29               ` Borislav Petkov
2024-01-09 12:44                 ` Borislav Petkov
2024-02-14 16:56                   ` Jeremi Piotrowski
2024-01-04 11:16   ` Borislav Petkov
2024-01-04 14:42   ` Borislav Petkov
2024-01-05 19:19   ` Borislav Petkov
2024-01-05 21:27   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 05/26] x86/mtrr: Don't print errors if MtrrFixDramModEn is set when SNP enabled Michael Roth
2023-12-30 16:19 ` [PATCH v1 06/26] x86/sev: Add RMP entry lookup helpers Michael Roth
2023-12-30 16:19 ` [PATCH v1 07/26] x86/fault: Add helper for dumping RMP entries Michael Roth
2024-01-10  9:59   ` Borislav Petkov
2024-01-10 20:18     ` Jarkko Sakkinen
2024-01-10 22:14       ` Borislav Petkov
2024-01-10 11:13   ` Borislav Petkov
2024-01-10 15:20     ` Tom Lendacky
2024-01-10 15:27       ` Borislav Petkov
2024-01-10 15:51         ` Tom Lendacky
2024-01-10 15:55           ` Borislav Petkov
2024-01-10 15:10   ` Tom Lendacky
2023-12-30 16:19 ` [PATCH v1 08/26] x86/traps: Define RMP violation #PF error code Michael Roth
2023-12-30 16:19 ` [PATCH v1 09/26] x86/fault: Dump RMP table information when RMP page faults occur Michael Roth
2023-12-30 16:19 ` [PATCH v1 10/26] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction Michael Roth
2024-01-12 14:49   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table Michael Roth
2024-01-12 19:48   ` Borislav Petkov
2024-01-12 20:00   ` Dave Hansen
2024-01-12 20:07     ` Borislav Petkov
2024-01-12 20:27       ` Vlastimil Babka
2024-01-15  9:06         ` Borislav Petkov
2024-01-15  9:14           ` Vlastimil Babka
2024-01-15  9:16           ` Mike Rapoport
2024-01-15  9:20             ` Borislav Petkov
2024-01-12 20:28       ` Tom Lendacky
2024-01-12 20:37         ` Dave Hansen
2024-01-15  9:23           ` Vlastimil Babka
2024-01-16 16:19           ` Michael Roth
2024-01-16 16:50             ` Michael Roth
2024-01-16 20:12               ` Mike Rapoport
2024-01-26  1:49                 ` Michael Roth
2024-01-16 18:22             ` Borislav Petkov
2024-01-16 20:22             ` Dave Hansen
2024-01-26  1:35               ` Michael Roth
2024-01-15  9:09     ` Borislav Petkov
2024-01-16 16:21       ` Dave Hansen
2024-01-17  9:34         ` Borislav Petkov
2024-01-15  9:01   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 12/26] crypto: ccp: Define the SEV-SNP commands Michael Roth
2024-01-15  9:41   ` Borislav Petkov
2024-01-26  1:56     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 13/26] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Michael Roth
2024-01-15 11:19   ` Borislav Petkov
2024-01-15 19:53   ` Borislav Petkov
2024-01-26  2:48     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 14/26] crypto: ccp: Provide API to issue SEV and SNP commands Michael Roth
2024-01-17  9:48   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 15/26] x86/sev: Introduce snp leaked pages list Michael Roth
2024-01-08 10:45   ` Vlastimil Babka
2024-01-09 22:19     ` Kalra, Ashish
2024-01-10  8:59       ` Vlastimil Babka
2023-12-30 16:19 ` [PATCH v1 16/26] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled Michael Roth
2023-12-30 16:19 ` [PATCH v1 17/26] crypto: ccp: Handle non-volatile INIT_EX data " Michael Roth
2024-01-18 14:03   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 18/26] crypto: ccp: Handle legacy SEV commands " Michael Roth
2024-01-19 17:18   ` Borislav Petkov
2024-01-19 17:36     ` Tom Lendacky
2024-01-19 17:48       ` Borislav Petkov
2024-01-26 13:29     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 19/26] iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown Michael Roth
2023-12-30 16:19 ` [PATCH v1 20/26] crypto: ccp: Add debug support for decrypting pages Michael Roth
2024-01-10 14:59   ` Sean Christopherson
2024-01-11  0:50     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 21/26] crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump Michael Roth
2024-01-21 11:49   ` Borislav Petkov
2024-01-26  3:03     ` Kalra, Ashish
2024-01-26 13:38     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 22/26] KVM: SEV: Make AVIC backing, VMSA and VMCB memory allocation SNP safe Michael Roth
2024-01-21 11:51   ` Borislav Petkov
2024-01-26  3:44     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 23/26] x86/cpufeatures: Enable/unmask SEV-SNP CPU feature Michael Roth
2023-12-30 16:19 ` [PATCH v1 24/26] crypto: ccp: Add the SNP_PLATFORM_STATUS command Michael Roth
2024-01-21 12:29   ` Borislav Petkov
2024-01-26  3:32     ` Michael Roth
2023-12-30 16:19 ` [PATCH v1 25/26] crypto: ccp: Add the SNP_COMMIT command Michael Roth
2024-01-21 12:35   ` Borislav Petkov
2023-12-30 16:19 ` [PATCH v1 26/26] crypto: ccp: Add the SNP_SET_CONFIG command Michael Roth
2024-01-21 12:41   ` Borislav Petkov
2024-01-26 13:30     ` Michael Roth

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