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

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Date:   Mon, 26 Jun 2023 09:30:20 +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: Re: [PATCH v5] PCI: Align pci memory space base address with page
 size

gentle ping.

在 2023/6/19 09:47, Bibo Mao 写道:
> 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);
>