linux-kernel - [PATCH v5 1/9] swiotlb: bail out of swiotlb_init

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Message-Id: <437209bd783fa3febc3a207acb7799a0ff5cf1f3.1690200598.git.petr.tesarik.ext@huawei.com>
Date:   Mon, 24 Jul 2023 14:12:37 +0200
From:   Petr Tesarik <petrtesarik@...weicloud.com>
To:     Stefano Stabellini <sstabellini@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        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 (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Jonathan Corbet <corbet@....net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        James Seo <james@...iv.tech>,
        James Clark <james.clark@....com>,
        Kees Cook <keescook@...omium.org>,
        xen-devel@...ts.xenproject.org (moderated list:XEN HYPERVISOR ARM),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM PORT),
        linux-kernel@...r.kernel.org (open list),
        linux-mips@...r.kernel.org (open list:MIPS),
        iommu@...ts.linux.dev (open list:XEN SWIOTLB SUBSYSTEM)
Cc:     Roberto Sassu <roberto.sassu@...weicloud.com>, petr@...arici.cz
Subject: [PATCH v5 1/9] swiotlb: bail out of swiotlb_init_late() if swiotlb is already allocated

From: Petr Tesarik <petr.tesarik.ext@...wei.com>

If swiotlb is allocated, immediately return 0, so callers do not have to
check io_tlb_default_mem.nslabs explicitly.

Signed-off-by: Petr Tesarik <petr.tesarik.ext@...wei.com>
---
 arch/arm/xen/mm.c         | 10 ++++------
 arch/x86/kernel/pci-dma.c | 12 ++++++------
 kernel/dma/swiotlb.c      |  3 +++
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 3d826c0b5fee..882cd70c7a2f 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -125,12 +125,10 @@ static int __init xen_mm_init(void)
 		return 0;
 
 	/* we can work with the default swiotlb */
-	if (!io_tlb_default_mem.nslabs) {
-		rc = swiotlb_init_late(swiotlb_size_or_default(),
-				       xen_swiotlb_gfp(), NULL);
-		if (rc < 0)
-			return rc;
-	}
+	rc = swiotlb_init_late(swiotlb_size_or_default(),
+			       xen_swiotlb_gfp(), NULL);
+	if (rc < 0)
+		return rc;
 
 	cflush.op = 0;
 	cflush.a.dev_bus_addr = 0;
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de6be0a3965e..08988b0a1c91 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -86,16 +86,16 @@ static void __init pci_xen_swiotlb_init(void)
 
 int pci_xen_swiotlb_init_late(void)
 {
+	int rc;
+
 	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;
-	}
+	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;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 2b83e3ad9dca..66fc8ec9ae45 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -384,6 +384,9 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
 	bool retried = false;
 	int rc = 0;
 
+	if (io_tlb_default_mem.nslabs)
+		return 0;
+
 	if (swiotlb_force_disable)
 		return 0;
 
-- 
2.25.1