linux-kernel - [PATCH v2] PCI: Align pci memory space base address with page size

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Message-Id: <20230605034423.1528206-1-maobibo@loongson.cn>
Date:   Mon,  5 Jun 2023 11:44:23 +0800
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>, helgaas@...nel.org
Cc:     linux-pci@...r.kernel.org, Jianmin Lv <lvjianmin@...ngson.cn>,
        WANG Xuerui <kernel@...0n.name>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, loongson-kernel@...ts.loongnix.cn
Subject: [PATCH v2] PCI: Align pci memory space base address with page size

Some PCI devices has only 4K memory space size, it is normal in general
machines and aligned with page size. However some architectures which
support different page size, default page size on LoongArch is 16K, and
ARM64 supports page size varying from 4K to 64K. On machines where larger
page size is use, memory space region of two different pci devices may be
in one page. It is not safe with mmu protection, also VFIO pci device
driver requires base address of pci memory space page aligned, so that it
can be memory mapped to qemu user space when it is pass-through to vm.

It consumes more pci memory resource with page size alignment requirement,
on 64 bit system it should not be a problem. And UEFI bios set pci memory
base address with 4K fixed-size aligned, the safer solution is to align
with larger size on UEFI BIOS stage on these architectures, linux kernel
can reuse resource from UEFI bios. For new devices such hotplug pci
devices and sriov devices, pci resource is assigned in Linux kernel side.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/arm64/kernel/pci.c  | 13 +++++++++++++
 arch/loongarch/pci/pci.c | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
index 2276689b5411..e2f7b176b156 100644
--- a/arch/arm64/kernel/pci.c
+++ b/arch/arm64/kernel/pci.c
@@ -232,4 +232,17 @@ void pcibios_remove_bus(struct pci_bus *bus)
 	acpi_pci_remove_bus(bus);
 }
 
+resource_size_t pcibios_align_resource(void *data, const struct resource *res,
+				resource_size_t size, resource_size_t align)
+{
+	resource_size_t start = res->start;
+
+	/*
+	 * align base address of pci memory resource with page size
+	 */
+	if ((res->flags & IORESOURCE_MEM) && (align < PAGE_SIZE))
+		start = ALIGN(start, PAGE_SIZE);
+
+	return start;
+}
 #endif
diff --git a/arch/loongarch/pci/pci.c b/arch/loongarch/pci/pci.c
index 2726639150bc..943a48e60fb1 100644
--- a/arch/loongarch/pci/pci.c
+++ b/arch/loongarch/pci/pci.c
@@ -83,6 +83,24 @@ int pcibios_alloc_irq(struct pci_dev *dev)
 	return acpi_pci_irq_enable(dev);
 }
 
+/*
+ * memory space size of some pci cards is 4K, it is separated with
+ * different pages for generic architectures, so that mmu protection can
+ * work with different pci cards. However page size for LoongArch system
+ * is 16K, memory space of different pci cards may share the same page
+ * on LoongArch, it is not safe here.
+ */
+resource_size_t pcibios_align_resource(void *data, const struct resource *res,
+				resource_size_t size, resource_size_t align)
+{
+	resource_size_t start = res->start;
+
+	if ((res->flags & IORESOURCE_MEM) && (align < PAGE_SIZE))
+		start = ALIGN(start, PAGE_SIZE);
+
+	return start;
+}
+
 static void pci_fixup_vgadev(struct pci_dev *pdev)
 {
 	struct pci_dev *devp = NULL;
-- 
2.27.0