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

From: Huacai Chen <chenhuacai@kernel.org>
To: Bjorn Helgaas <bhelgaas@google.com>, Huacai Chen <chenhuacai@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	loongson-kernel@lists.loongnix.cn,  linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,  loongarch@lists.linux.dev,
	Huacai Chen <chenhuacai@loongson.cn>
Subject: Re: [PATCH v5] PCI: Align pci memory space base address with page size
Date: Sun, 9 Jul 2023 17:19:57 +0800	[thread overview]
Message-ID: <CAAhV-H7_Rjv-ySorjbw0f4OiV4J0-N75fmUNBCmeJbeeydJu4Q@mail.gmail.com> (raw)
In-Reply-To: <bdc6eb71-482d-5dd6-d527-c2f2f68dfb38@loongson.cn>

On Fri, Jul 7, 2023 at 10:47 AM bibo mao <maobibo@loongson.cn> wrote:
>
> Bjourn, Hucai,
>
> ping again.
>
> The is such issue on only LoongArch system since 16K page size is used.
>
> Should we add code in general framework  or in LoongArch specified code
> in v1?
Though I still don't know why others have no problems. But it is
surely a bug on LoongArch. So if Bjorn has no objections, please use
the old method (just like v1 but you can simply align to page size
unconditionally).

Huacai
>
> If you do not think that it is problem, I can give up. LoongArch system
> is not only for myself own, I do not care about it also since LoongArch
> Maintainer think it is not a issue.
>
> Regards
> Bibo Mao
>
> 在 2023/6/26 09:30, bibo mao 写道:
> > 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@loongson.cn>
> >> Reviewed-by: Huacai Chen <chenhuacai@loongson.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);
> >>
> >
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