linux-kernel - [RFC V1 3/5] x86: CVMs: Enable dynamic swiotlb by default for CVMs

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Message-ID: <20240112055251.36101-4-vannapurve@google.com>
Date: Fri, 12 Jan 2024 05:52:49 +0000
From: Vishal Annapurve <vannapurve@...gle.com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com, rientjes@...gle.com, bgardon@...gle.com, 
	seanjc@...gle.com, erdemaktas@...gle.com, ackerleytng@...gle.com, 
	jxgao@...gle.com, sagis@...gle.com, oupton@...gle.com, peterx@...hat.com, 
	vkuznets@...hat.com, dmatlack@...gle.com, pgonda@...gle.com, 
	michael.roth@....com, kirill@...temov.name, thomas.lendacky@....com, 
	dave.hansen@...ux.intel.com, linux-coco@...ts.linux.dev, 
	chao.p.peng@...ux.intel.com, isaku.yamahata@...il.com, andrew.jones@...ux.dev, 
	corbet@....net, hch@....de, m.szyprowski@...sung.com, bp@...e.de, 
	rostedt@...dmis.org, iommu@...ts.linux.dev, 
	Vishal Annapurve <vannapurve@...gle.com>
Subject: [RFC V1 3/5] x86: CVMs: Enable dynamic swiotlb by default for CVMs

CVMs used SWIOTLB for non-trusted IO using dma_map_* APIs. This series
will ensure that dma_alloc_* API to also allocate from SWIOTLB pools.
Initial size of SWIOTLB pool is decided using heuristics and has been
working with CVM usecases so far.

It's better to allow SWIOTLB to scale up on demand rather than keeping
the size fixed to avoid failures with possibly increased usage of
SWIOTLB with dma_alloc_* APIs allocating from SWIOTLB pools. This should
also help in future with more devices getting used from CVMs for
non-trusted IO.

Signed-off-by: Vishal Annapurve <vannapurve@...gle.com>
---
 arch/x86/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1566748f16c4..035c8a022c4c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -884,6 +884,7 @@ config INTEL_TDX_GUEST
 	select X86_MEM_ENCRYPT
 	select X86_MCE
 	select UNACCEPTED_MEMORY
+	select SWIOTLB_DYNAMIC
 	help
 	  Support running as a guest under Intel TDX.  Without this support,
 	  the guest kernel can not boot or run under TDX.
@@ -1534,6 +1535,7 @@ config AMD_MEM_ENCRYPT
 	select ARCH_HAS_CC_PLATFORM
 	select X86_MEM_ENCRYPT
 	select UNACCEPTED_MEMORY
+	select SWIOTLB_DYNAMIC
 	help
 	  Say yes to enable support for the encryption of system memory.
 	  This requires an AMD processor that supports Secure Memory
-- 
2.43.0.275.g3460e3d667-goog