linux-kernel - Re: [PATCHv2] x86/mm: Fix memory encryption features advertisement

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Message-ID: <d6bc1751-a9f1-43b3-aac3-e423911ce605@amd.com>
Date: Thu, 11 Jan 2024 14:41:52 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Dexuan Cui <decui@...rosoft.com>,
 Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
Subject: Re: [PATCHv2] x86/mm: Fix memory encryption features advertisement

On 1/11/24 05:12, Kirill A. Shutemov wrote:
> When memory encryption is enabled, the kernel prints the encryption
> flavor that the system supports.
> 
> The check assumes that everything is AMD SME/SEV if it doesn't have
> the TDX CPU feature set.
> 
> Hyper-V vTOM sets cc_vendor to CC_VENDOR_INTEL when it runs as L2 guest
> on top of TDX, but not X86_FEATURE_TDX_GUEST. Hyper-V only needs memory
> encryption enabled for I/O without the rest of CoCo enabling.
> 
> To avoid confusion, check the cc_vendor directly.
> 
> Possible alternative is to completely removing the print statement.
> For a regular TDX guest, the kernel already prints a message indicating
> that it is booting on TDX. Similarly, AMD and Hyper-V can also display
> a message during their enumeration process.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Dexuan Cui <decui@...rosoft.com>
> Cc: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>

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

> ---
>   arch/x86/mm/mem_encrypt.c | 56 +++++++++++++++++++++------------------
>   1 file changed, 30 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c