From: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
To: Borislav Petkov <bp@alien8.de>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
KVM <kvm@vger.kernel.org>, Ashish Kalra <ashish.kalra@amd.com>,
Joerg Roedel <joro@8bytes.org>,
Michael Roth <michael.roth@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH 5/5] x86/CPU/AMD: Track SNP host status with cc_platform_*()
Date: Thu, 28 Mar 2024 15:24:29 +0100 [thread overview]
Message-ID: <ac4f34a0-036a-48b9-ab56-8257700842fc@linux.microsoft.com> (raw)
In-Reply-To: <20240328134109.GAZgVzdfQob43XAIr9@fat_crate.local>
On 28/03/2024 14:41, Borislav Petkov wrote:
> On Thu, Mar 28, 2024 at 12:51:17PM +0100, Jeremi Piotrowski wrote:
>> Shouldn't this line be inside the cpu_has(c, X86_FEATURE_SEV_SNP) check?
>
> The cc_vendor is not dependent on X86_FEATURE_SEV_SNP.
>
It's not but if you set it before the check it will be set for all AMD systems,
even if they are neither CC hosts nor CC guests.
cc_vendor being unset is handled correctly in cc_platform_has() checks.
>> How about turning this into a more specific check:
>>
>> if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP) &&
>
> Why?
>
To leave open the possibility of an SNP hypervisor running nested.
> The check is "am I running as a hypervisor on baremetal".
>
I thought you wanted to filter out SEV-SNP guests, which also have X86_FEATURE_SEV_SNP
CPUID bit set.
My understanding is that these are the cases:
CPUID(SEV_SNP) | MSR(SEV_SNP) | what am I
---------------------------------------------
set | set | SNP-guest
set | unset | SNP-host
unset | ?? | not SNP
next prev parent reply other threads:[~2024-03-28 14:24 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-27 15:43 [PATCH 0/5] x86/sev: Fix SNP host late disable Borislav Petkov
2024-03-27 15:43 ` [PATCH 1/5] x86/alternatives: Remove a superfluous newline in _static_cpu_has() Borislav Petkov
2024-03-27 15:43 ` [PATCH 2/5] x86/alternatives: Catch late X86_FEATURE modifiers Borislav Petkov
2024-03-27 15:57 ` Nikolay Borisov
2024-04-03 17:59 ` Borislav Petkov
2024-03-27 15:43 ` [PATCH 3/5] x86/kvm/Kconfig: Have KVM_AMD_SEV select ARCH_HAS_CC_PLATFORM Borislav Petkov
2024-03-29 14:42 ` Tom Lendacky
2024-03-27 15:43 ` [PATCH 4/5] x86/cc: Add cc_platform_set/_clear() helpers Borislav Petkov
2024-03-29 14:46 ` Tom Lendacky
2024-03-27 15:43 ` [PATCH 5/5] x86/CPU/AMD: Track SNP host status with cc_platform_*() Borislav Petkov
2024-03-28 11:51 ` Jeremi Piotrowski
2024-03-28 13:41 ` Borislav Petkov
2024-03-28 14:24 ` Jeremi Piotrowski [this message]
2024-03-28 15:39 ` Borislav Petkov
2024-04-04 17:07 ` Jeremi Piotrowski
2024-04-24 18:46 ` Borislav Petkov
2024-03-29 14:52 ` Tom Lendacky
2024-04-03 4:15 ` [PATCH 0/5] x86/sev: Fix SNP host late disable Aithal, Srikanth
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