linux-kernel - Re: [PATCH 5/5] x86/CPU/AMD: Track SNP host status with cc_platform

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Date: Fri, 29 Mar 2024 09:52:02 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>,
 Ashish Kalra <ashish.kalra@....com>, Joerg Roedel <joro@...tes.org>,
 Michael Roth <michael.roth@....com>
Subject: Re: [PATCH 5/5] x86/CPU/AMD: Track SNP host status with
 cc_platform_*()

On 3/27/24 10:43, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@...en8.de>
> 
> The host SNP worthiness can determined later, after alternatives have
> been patched, in snp_rmptable_init() depending on cmdline options like
> iommu=pt which is incompatible with SNP, for example.
> 
> Which means that one cannot use X86_FEATURE_SEV_SNP and will need to
> have a special flag for that control.
> 
> Use that newly added CC_ATTR_HOST_SEV_SNP in the appropriate places.
> 
> Move kdump_sev_callback() to its rightfull place, while at it.
> 
> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>

If late disabling of CPU feature flags is ever supported in the future, we 
should come back and possibly remove this. But until then...

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   arch/x86/include/asm/sev.h         |  4 ++--
>   arch/x86/kernel/cpu/amd.c          | 38 ++++++++++++++++++------------
>   arch/x86/kernel/cpu/mtrr/generic.c |  2 +-
>   arch/x86/kernel/sev.c              | 10 --------
>   arch/x86/kvm/svm/sev.c             |  2 +-
>   arch/x86/virt/svm/sev.c            | 26 +++++++++++++-------
>   drivers/crypto/ccp/sev-dev.c       |  2 +-
>   drivers/iommu/amd/init.c           |  4 +++-
>   8 files changed, 49 insertions(+), 39 deletions(-)
>