linux-kernel - Re: [PATCH v15 01/13] x86/sev: Carve out and export SNP guest messaging init routines

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Message-ID: <cc2ab6ca-3c65-4171-9401-d480fd65f932@amd.com>
Date: Tue, 10 Dec 2024 12:08:32 +0530
From: Nikunj A Dadhania <nikunj@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, thomas.lendacky@....com, x86@...nel.org,
 kvm@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
 dave.hansen@...ux.intel.com, pgonda@...gle.com, seanjc@...gle.com,
 pbonzini@...hat.com
Subject: Re: [PATCH v15 01/13] x86/sev: Carve out and export SNP guest
 messaging init routines

On 12/9/2024 9:08 PM, Borislav Petkov wrote:
> On Mon, Dec 09, 2024 at 11:46:44AM +0530, Nikunj A. Dadhania wrote:
>> That leaves us with only one site: snp_init_crypto(), should I fold this
>> change in current patch ?
> 
> Nah, a pre-patch pls.
> 
> Along with an explanation summing up our discussion in the commit message.
> This patch is already doing enough.

From: Nikunj A Dadhania <nikunj@....com>
Date: Thu, 5 Dec 2024 12:00:56 +0530
Subject: [PATCH] virt: sev-guest: Replace GFP_KERNEL_ACCOUNT with GFP_KERNEL

Replace GFP_KERNEL_ACCOUNT with GFP_KERNEL in the sev-guest driver code.
GFP_KERNEL_ACCOUNT is typically used for accounting untrusted userspace
allocations. After auditing the sev-guest code, the following changes are
necessary:

  * snp_init_crypto(): Use GFP_KERNEL as this is a trusted device probe
    path.

Retain GFP_KERNEL_ACCOUNT in the following cases for robustness and
specific path requirements:

  * alloc_shared_pages(): Although all allocations are limited, retain
    GFP_KERNEL_ACCOUNT for future robustness.

  * get_report() and get_ext_report(): These functions are on the unlocked
    ioctl path and should continue using GFP_KERNEL_ACCOUNT.

Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Nikunj A Dadhania <nikunj@....com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c
b/drivers/virt/coco/sev-guest/sev-guest.c
index 62328d0b2cb6..250ce92d816b 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -141,7 +141,7 @@ static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t
keylen)
 {
 	struct aesgcm_ctx *ctx;

-	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
 		return NULL;

-- 
2.34.1