linux-kernel - [PATCH v5] PCI: Align pci memory space base address with page size

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Message-Id: <20230619014715.3792883-1-maobibo@loongson.cn>
Date:   Mon, 19 Jun 2023 09:47:15 +0800
From:   Bibo Mao <maobibo@...ngson.cn>
To:     Bjorn Helgaas <bhelgaas@...gle.com>, Will Deacon <will@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, loongson-kernel@...ts.loongnix.cn,
        Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH v5] PCI: Align pci memory space base address with page size

Some PCI devices have 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 passed-through to vm.

It consumes more pci memory resource with page size alignment requirement,
here extra option PCI_MEMRES_PAGE_ALIGN is added, it can be enabled by
different architectures, currently arm64/loongarch enable this option.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
Reviewed-by: Huacai Chen <chenhuacai@...ngson.cn>
---
Change history
v5: enable option PCI_MEMRES_PAGE_ALIGN on arm64. Verified on LoongArch
and pass to compile on arm64 with defconfig

v4: add extra kernel option PCI_MEMRES_PAGE_ALIGN to set memory resource
    page aligned

v3: move alignment requirement to generic pci code

v2: add pci resource alignment requirement in arch specified function
    pcibios_align_resource on arm64/LoongArch platforms

---
 arch/arm64/Kconfig      | 1 +
 arch/loongarch/Kconfig  | 1 +
 drivers/pci/Kconfig     | 3 +++
 drivers/pci/setup-res.c | 7 +++++++
 4 files changed, 12 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 343e1e1cae10..24858bbf2b72 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -232,6 +232,7 @@ config ARM64
 	select OF_EARLY_FLATTREE
 	select PCI_DOMAINS_GENERIC if PCI
 	select PCI_ECAM if (ACPI && PCI)
+	select PCI_MEMRES_PAGE_ALIGN if PCI
 	select PCI_SYSCALL if PCI
 	select POWER_RESET
 	select POWER_SUPPLY
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d38b066fc931..7dbde5e5b351 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -140,6 +140,7 @@ config LOONGARCH
 	select PCI_DOMAINS_GENERIC
 	select PCI_ECAM if ACPI
 	select PCI_LOONGSON
+	select PCI_MEMRES_PAGE_ALIGN
 	select PCI_MSI_ARCH_FALLBACKS
 	select PCI_QUIRKS
 	select PERF_USE_VMALLOC
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 9309f2469b41..9be5f85ff9dc 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -128,6 +128,9 @@ config PCI_LOCKLESS_CONFIG
 config PCI_BRIDGE_EMUL
 	bool
 
+config PCI_MEMRES_PAGE_ALIGN
+	bool
+
 config PCI_IOV
 	bool "PCI IOV support"
 	select PCI_ATS
diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index 967f9a758923..6ad76734a670 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -339,6 +339,13 @@ int pci_assign_resource(struct pci_dev *dev, int resno)
 		return -EINVAL;
 	}
 
+#ifdef CONFIG_PCI_MEMRES_PAGE_ALIGN
+	/*
+	 * force minimum page alignment for vfio pci usage
+	 */
+	if (res->flags & IORESOURCE_MEM)
+		align = max_t(resource_size_t, PAGE_SIZE, align);
+#endif
 	size = resource_size(res);
 	ret = _pci_assign_resource(dev, resno, size, align);
 
-- 
2.27.0