Re: [PATCH v3] x86/pci-dma: add a SWIOTLB_ANY flag to lift the low mem limitation

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 12.02.2026 10:37, Jun Miao wrote:
> Intel TDX guest wants to allocate a swiotlb buffer that is not restricted to
> low memory for the trusted hypervisor scheme.  Adding a new flag will be used
> in swiotlb_memblock_alloc() to allow allocation of SWIOTLB memory beyond low
> memory restriction.
>
> Power SVM already supports this, but X86 still faces the same limitation.
> Commit: 8ba2ed1be9 (swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction)
>
> Reviewed-by: Aakarsh Jain <aakarsh.jain@oss.qualcomm.com>
> Tested-by: Aakarsh Jain <aakarsh.jain@oss.qualcomm.com>
> Signed-off-by: Jun Miao <jun.miao@intel.com>

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
>
> V1 -> V2:
> 1.Updated commit message and description.
> 2.Add Reviewed and Tested.
>
> V1 Latest Feedback : https://protect2.fireeye.com/v1/url?k=f35668f3-92dd7dc5-f357e3bc-74fe485cbff1-e6ff63e2f942f6a7&q=1&e=66eee4e1-a18d-47f9-ad21-f3dfab1d6f09&u=https%3A%2F%2Flists.openwall.net%2Flinux-kernel%2F2026%2F02%2F11%2F483
>
> v2 -> v3:
> We can alloc 4GB with the dynamic swiotlb, rather than 1GB.
> 1G is not correct. So change the commit log.
>
> ---
>   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

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland