linux-kernel - [RFC PATCH 1/5] x86/xen: disable swiotlb for xen pvh

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Message-ID: <20230312120157.452859-2-ray.huang@amd.com>
Date:   Sun, 12 Mar 2023 20:01:53 +0800
From:   Huang Rui <ray.huang@....com>
To:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Roger Pau Monné <roger.pau@...rix.com>,
        <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <amd-gfx@...ts.freedesktop.org>
CC:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Stewart Hildebrand" <Stewart.Hildebrand@....com>,
        Xenia Ragiadakou <burzalodowa@...il.com>,
        Honglei Huang <honglei1.huang@....com>,
        Julia Zhang <julia.zhang@....com>,
        Chen Jiqian <Jiqian.Chen@....com>,
        Huang Rui <ray.huang@....com>
Subject: [RFC PATCH 1/5] x86/xen: disable swiotlb for xen pvh

Xen PVH is the paravirtualized mode and takes advantage of hardware
virtualization support when possible. It will using the hardware IOMMU
support instead of xen-swiotlb, so disable swiotlb if current domain is
Xen PVH.

Signed-off-by: Huang Rui <ray.huang@....com>
---
 arch/x86/kernel/pci-dma.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 30bbe4abb5d6..f5c73dd18f2a 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -74,6 +74,12 @@ static inline void __init pci_swiotlb_detect(void)
 #ifdef CONFIG_SWIOTLB_XEN
 static void __init pci_xen_swiotlb_init(void)
 {
+	/* Xen PVH domain won't use swiotlb */
+	if (xen_pvh_domain()) {
+		x86_swiotlb_enable = false;
+		return;
+	}
+
 	if (!xen_initial_domain() && !x86_swiotlb_enable)
 		return;
 	x86_swiotlb_enable = true;
@@ -86,7 +92,7 @@ static void __init pci_xen_swiotlb_init(void)
 
 int pci_xen_swiotlb_init_late(void)
 {
-	if (dma_ops == &xen_swiotlb_dma_ops)
+	if (xen_pvh_domain() || dma_ops == &xen_swiotlb_dma_ops)
 		return 0;
 
 	/* we can work with the default swiotlb */
-- 
2.25.1