From: Borislav Petkov <bp@alien8.de>
To: Jun Miao <jun.miao@intel.com>
Cc: tglx@kernel.org, mingo@redhat.com, dave.hansen@linux.intel.com,
m.szyprowski@samsung.com, robin.murphy@arm.com,
rick.p.edgecombe@intel.com, x86@kernel.org,
linux-kernel@vger.kernel.org, aakarsh.jain@oss.qualcomm.com,
michael.roth@amd.com, fan.du@intel.com
Subject: Re: [PATCH v4] x86/pci-dma: add a SWIOTLB_ANY flag to lift the low mem limitation
Date: Sat, 11 Jul 2026 17:55:47 -0700 [thread overview]
Message-ID: <20260712005547.GBalLmE0FTJYx7Cnwg@fat_crate.local> (raw)
In-Reply-To: <20260625012616.2992535-1-jun.miao@intel.com>
On Thu, Jun 25, 2026 at 09:26:16AM +0800, Jun Miao wrote:
> When high-speed NICs or multi-GPU setups are passed through into confidential
> VMs, the SWIOTLB bounce buffer becomes the critical path between private and
> shared memory. Restricting it to low memory limits throughput and fails to
> scale for larger workloads.
>
> AMD SEV-SNP and Intel TDX guests run in a TEE where the hypervisor is untrusted.
> DMA-capable devices require bounce buffers to mediate between encrypted private
> memory and unencrypted shared memory. Confining these buffers to low memory (<4GB)
> unnecessarily caps their size and degrades performance.
>
> Power SVM already supports this; x86 does not. See commit 8ba2ed1be9
> ("swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction").
>
> [ aakarsh: completely trim down/rewrite changelog ]
>
> Tested-by: Aakarsh Jain <aakarsh.jain@oss.qualcomm.com>
> Suggested-by: Borislav Petkov <bp@alien8.de>
> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Reviewed-by: Aakarsh Jain <aakarsh.jain@oss.qualcomm.com>
> Signed-off-by: Jun Miao <jun.miao@intel.com>
> ---
Sashiko has a question:
https://lore.kernel.org/r/20260625012616.2992535-1-jun.miao@intel.com
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
prev parent reply other threads:[~2026-07-12 0:56 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-25 1:26 Jun Miao
2026-06-25 3:14 ` Michael Kelley
2026-07-12 0:55 ` Borislav Petkov [this message]
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