linux-kernel - [PATCH 2/3] x86: always initialize xen-swiotlb when xen-pcifront is enabling

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Date:   Mon, 12 Jun 2023 16:25:41 +0200
From:   Christoph Hellwig <hch@....de>
To:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     xen-devel@...ts.xenproject.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] x86: always initialize xen-swiotlb when xen-pcifront is enabling

Remove the dangerous late initialization of xen-swiotlb in
pci_xen_swiotlb_init_late and instead just always initialize
xen-swiotlb in the boot code if CONFIG_XEN_PCIDEV_FRONTEND is
enabled and Xen PV PCI is possible.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/x86/include/asm/xen/swiotlb-xen.h |  6 ------
 arch/x86/kernel/pci-dma.c              | 29 +++++++-------------------
 drivers/pci/xen-pcifront.c             |  6 ------
 3 files changed, 7 insertions(+), 34 deletions(-)

diff --git a/arch/x86/include/asm/xen/swiotlb-xen.h b/arch/x86/include/asm/xen/swiotlb-xen.h
index 77a2d19cc9909e..abde0f44df57dc 100644
--- a/arch/x86/include/asm/xen/swiotlb-xen.h
+++ b/arch/x86/include/asm/xen/swiotlb-xen.h
@@ -2,12 +2,6 @@
 #ifndef _ASM_X86_SWIOTLB_XEN_H
 #define _ASM_X86_SWIOTLB_XEN_H
 
-#ifdef CONFIG_SWIOTLB_XEN
-extern int pci_xen_swiotlb_init_late(void);
-#else
-static inline int pci_xen_swiotlb_init_late(void) { return -ENXIO; }
-#endif
-
 int xen_swiotlb_fixup(void *buf, unsigned long nslabs);
 int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
 				unsigned int address_bits,
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de6be0a3965ee4..f323d83e40a70b 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -72,9 +72,15 @@ static inline void __init pci_swiotlb_detect(void)
 #endif /* CONFIG_SWIOTLB */
 
 #ifdef CONFIG_SWIOTLB_XEN
+static bool xen_swiotlb_enabled(void)
+{
+	return xen_initial_domain() || x86_swiotlb_enable ||
+		(IS_ENABLED(CONFIG_XEN_PCIDEV_FRONTEND) && xen_pv_pci_possible);
+}
+
 static void __init pci_xen_swiotlb_init(void)
 {
-	if (!xen_initial_domain() && !x86_swiotlb_enable)
+	if (!xen_swiotlb_enabled())
 		return;
 	x86_swiotlb_enable = true;
 	x86_swiotlb_flags |= SWIOTLB_ANY;
@@ -83,27 +89,6 @@ static void __init pci_xen_swiotlb_init(void)
 	if (IS_ENABLED(CONFIG_PCI))
 		pci_request_acs();
 }
-
-int pci_xen_swiotlb_init_late(void)
-{
-	if (dma_ops == &xen_swiotlb_dma_ops)
-		return 0;
-
-	/* we can work with the default swiotlb */
-	if (!io_tlb_default_mem.nslabs) {
-		int rc = swiotlb_init_late(swiotlb_size_or_default(),
-					   GFP_KERNEL, xen_swiotlb_fixup);
-		if (rc < 0)
-			return rc;
-	}
-
-	/* XXX: this switches the dma ops under live devices! */
-	dma_ops = &xen_swiotlb_dma_ops;
-	if (IS_ENABLED(CONFIG_PCI))
-		pci_request_acs();
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);
 #else
 static inline void __init pci_xen_swiotlb_init(void)
 {
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index 83c0ab50676dff..11636634ae512f 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -22,7 +22,6 @@
 #include <linux/bitops.h>
 #include <linux/time.h>
 #include <linux/ktime.h>
-#include <linux/swiotlb.h>
 #include <xen/platform_pci.h>
 
 #include <asm/xen/swiotlb-xen.h>
@@ -669,11 +668,6 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
 
 	spin_unlock(&pcifront_dev_lock);
 
-	if (!err && !is_swiotlb_active(&pdev->xdev->dev)) {
-		err = pci_xen_swiotlb_init_late();
-		if (err)
-			dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");
-	}
 	return err;
 }
 
-- 
2.39.2