On Tuesday, January 10, 2023 7:02:43 PM CET Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> Normally we reject ECAM space unless it is reported as reserved in the E820
> table or via a PNP0C02 _CRS method (PCI Firmware, r3.3, sec 4.1.2). This
> means PCI extended config space (offsets 0x100-0xfff) may not be accessible.
>
> Some firmware doesn't report ECAM space via PNP0C02 _CRS methods, but does
> mention it as an EfiMemoryMappedIO region via EFI GetMemoryMap(), which is
> normally converted to an E820 entry by a bootloader or EFI stub.
>
> 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map"), removes
> E820 entries that correspond to EfiMemoryMappedIO regions because some
> other firmware uses EfiMemoryMappedIO for PCI host bridge windows, and the
> E820 entries prevent Linux from allocating BAR space for hot-added devices.
>
> Allow use of ECAM for extended config space when the region is covered by
> an EfiMemoryMappedIO region, even if it's not included in E820 or PNP0C02
> _CRS.
>
> Reported by Kan Liang, Tony Luck, and Giovanni Cabiddu.
>
> Fixes: 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map")
> Link: https://lore.kernel.org/r/ac2693d8-8ba3-72e0-5b66-b3ae008d539d@xxxxxxxxxxxxxxx
> Reported-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Reported-by: Tony Luck <tony.luck@xxxxxxxxx>
> Reported-by: Giovanni Cabiddu <giovanni.cabiddu@xxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> ---
> arch/x86/pci/mmconfig-shared.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
> index cd16bef5f2d9..da4b6e8e9df0 100644
> --- a/arch/x86/pci/mmconfig-shared.c
> +++ b/arch/x86/pci/mmconfig-shared.c
> @@ -12,6 +12,7 @@
> */
>
> #include <linux/acpi.h>
> +#include <linux/efi.h>
> #include <linux/pci.h>
> #include <linux/init.h>
> #include <linux/bitmap.h>
> @@ -442,6 +443,32 @@ static bool is_acpi_reserved(u64 start, u64 end, enum e820_type not_used)
> return mcfg_res.flags;
> }
>
> +static bool is_efi_mmio(u64 start, u64 end, enum e820_type not_used)
> +{
> +#ifdef CONFIG_EFI
> + efi_memory_desc_t *md;
> + u64 size, mmio_start, mmio_end;
> +
> + for_each_efi_memory_desc(md) {
> + if (md->type == EFI_MEMORY_MAPPED_IO) {
> + size = md->num_pages << EFI_PAGE_SHIFT;
> + mmio_start = md->phys_addr;
> + mmio_end = mmio_start + size;
> +
> + /*
> + * N.B. Caller supplies (start, start + size),
> + * so to match, mmio_end is the first address
> + * *past* the EFI_MEMORY_MAPPED_IO area.
> + */
> + if (mmio_start <= start && end <= mmio_end)
> + return true;
> + }
> + }
> +#endif
> +
> + return false;
> +}
> +
> typedef bool (*check_reserved_t)(u64 start, u64 end, enum e820_type type);
>
> static bool __ref is_mmconf_reserved(check_reserved_t is_reserved,
> @@ -513,6 +540,10 @@ pci_mmcfg_check_reserved(struct device *dev, struct pci_mmcfg_region *cfg, int e
> "MMCONFIG at %pR not reserved in "
> "ACPI motherboard resources\n",
> &cfg->res);
> +
> + if (is_mmconf_reserved(is_efi_mmio, cfg, dev,
> + "EfiMemoryMappedIO"))
> + return true;
> }
>
> /*
>
