Re: Bug report: the extended PCI config space is missed with 6.2-rc2

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-01-05 5:32 p.m., Bjorn Helgaas wrote:
> [+cc Tony, Dan]
> 
> On Wed, Jan 04, 2023 at 09:39:56AM -0500, Liang, Kan wrote:
>> Hi Bjorn,
>>
>> Happy new year!
>>
>> We found some PCI issues with the latest 6.2-rc2.
>>
>> - Using the lspci -xxxx, the extended PCI config space of all PCI
>> devices are missed with the latest 6.2-rc2. The system we used had 932
>> PCI devices, at least 800 which have extended space as seen when booted
>> into a 5.15 kernel. But none of them appeared in 6.2-rc2.
>> - The drivers which rely on the information in the extended PCI config
>> space don't work anymore. We have confirmed that the perf uncore driver
>> (uncore performance monitoring) and Intel VSEC driver (telemetry) don't
>> work in 6.2-rc2. There could be more drivers which are impacted.
>>
>> After a bisect, we found the regression is caused by the below commit
>> 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map").
>> After reverting the commit, the issues are gone.
> 
> Can you try this patch (based on v6.2-rc1):
> 
> > commit 89a0067217b0 ("x86/pci: Treat EfiMemoryMappedIO as reservation
of ECAM space")
> parent 1b929c02afd3
> Author: Bjorn Helgaas <bhelgaas@google.com>
> Date:   Thu Jan 5 16:02:58 2023 -0600
> 
>     x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM space
>     
>     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 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.
>     
>     Fixes: 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map")
>     Link: https://lore.kernel.org/r/ac2693d8-8ba3-72e0-5b66-b3ae008d539d@linux.intel.com
> 

The patch fixes the issue I reported.

Tested-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan

> diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
> index 758cbfe55daa..4adc587a4c94 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 +443,25 @@ static bool is_acpi_reserved(u64 start, u64 end, enum e820_type not_used)
>  	return mcfg_res.flags;
>  }
>  
> +static bool is_efi_reserved(u64 start, u64 end, enum e820_type not_used)
> +{
> +	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 - 1;
> +
> +			if (mmio_start <= start && end <= mmio_end)
> +				return true;
> +		}
> +	}
> +
> +	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,
> @@ -452,7 +472,7 @@ static bool __ref is_mmconf_reserved(check_reserved_t is_reserved,
>  	u64 size = resource_size(&cfg->res);
>  	u64 old_size = size;
>  	int num_buses;
> -	char *method = with_e820 ? "E820" : "ACPI motherboard resources";
> +	char *method = with_e820 ? "E820" : "ACPI motherboard resources or EFI";
>  
>  	while (!is_reserved(addr, addr + size, E820_TYPE_RESERVED)) {
>  		size >>= 1;
> @@ -502,15 +522,17 @@ pci_mmcfg_check_reserved(struct device *dev, struct pci_mmcfg_region *cfg, int e
>  	if (!early && !acpi_disabled) {
>  		if (is_mmconf_reserved(is_acpi_reserved, cfg, dev, 0))
>  			return true;
> +		if (is_mmconf_reserved(is_efi_reserved, cfg, dev, 0))
> +			return true;
>  
>  		if (dev)
>  			dev_info(dev, FW_INFO
> -				 "MMCONFIG at %pR not reserved in "
> +				 "MMCONFIG at %pR not reserved in EFI "
>  				 "ACPI motherboard resources\n",
>  				 &cfg->res);
>  		else
>  			pr_info(FW_INFO PREFIX
> -			       "MMCONFIG at %pR not reserved in "
> +			       "MMCONFIG at %pR not reserved in EFI or "
>  			       "ACPI motherboard resources\n",
>  			       &cfg->res);
>  	}