linux-kernel - Re: [PATCH] swiotlb: add a SWIOTLB_ANY flag to lift restricted low memory for encryption

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <8b4fb83a-caeb-49fd-8e78-67664a07cbe4@oss.qualcomm.com>
Date: Wed, 11 Feb 2026 15:05:53 +0530
From: Aakarsh Jain <aakarsh.jain@....qualcomm.com>
To: Jun Miao <jun.miao@...el.com>, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, fan.du@...el.com,
        thomas.lendacky@....com, aakarsh.jain@....qualcomm.com
Subject: Re: [PATCH] swiotlb: add a SWIOTLB_ANY flag to lift restricted low
 memory for encryption

Hi Jun,

On 4/29/2025 10:23 PM, Jun Miao wrote:
> TDX guest wants to allocate a swiotlb buffer that is not restricted
> to low memory for the trusted hypervisor scheme. So that allow to pick
> a location everywhere for hypervisors with guest memory encryption in
> swiotlb_memblock_alloc() interface by adding a new flag.
> 
> Signed-off-by: Jun Miao <jun.miao@...el.com>
> ---
>   arch/x86/kernel/pci-dma.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index 6267363e0189..73b9320c4a7d 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -61,7 +61,7 @@ static void __init pci_swiotlb_detect(void)
>   	 */
>   	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
>   		x86_swiotlb_enable = true;
> -		x86_swiotlb_flags |= SWIOTLB_FORCE;
> +		x86_swiotlb_flags |= SWIOTLB_ANY | SWIOTLB_FORCE;
>   	}
>   }
>   #else


Thanks for working on this patch.

We ran into the same limitation where the SWIOTLB bounce buffer cannot
be increased beyond 1GB without this change.

I reviewed the change and tested it on our setup. With this patch 
applied, we are able to successfully configure and use SWIOTLB bounce 
buffer size greater than 1GB, and the previous allocation failures are 
resolved.

Since, I wanted to bring more visibility to this patch.

Feel free to add
Reviewed-by: Aakarsh Jain <aakarsh.jain@....qualcomm.com>
Tested-by: Aakarsh Jain <aakarsh.jain@....qualcomm.com>


Thanks,
Aakarsh