Re: [PATCH] x86/sev: Remove bogus virtual address check

[Borislav Petkov]

On Fri, Oct 10, 2025 at 05:10:37PM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> 
> The AES-GCM crypto library operates strictly on virtual addresses, and
> never performs any H/W offload, and so calling virt_addr_valid() is not
> needed.
> 
> Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
>  arch/x86/coco/sev/core.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index 9ae3b11754e6..c4e2de3687a9 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -2249,15 +2249,6 @@ int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req
>  	u64 seqno;
>  	int rc;
>  
> -	/*
> -	 * enc_payload() calls aesgcm_encrypt(), which can potentially offload to HW.
> -	 * The offload's DMA SG list of data to encrypt has to be in linear mapping.
> -	 */
> -	if (!virt_addr_valid(req->req_buf) || !virt_addr_valid(req->resp_buf)) {
> -		pr_warn("AES-GSM buffers must be in linear mapping");
> -		return -EINVAL;
> -	}
> -
>  	guard(mutex)(&snp_cmd_mutex);
>  
>  	/* Check if the VMPCK is not empty */
> -- 

This came from:

  7ffeb2fc2670 ("x86/sev: Document requirement for linear mapping of guest request buffers")

and there was some speculation about the potential of using a crypto
accelerator which wants addresses in linear mapping...

-- 
Regards/Gruss,
    Boris.

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