Re: [PATCH v4] pci: read amd iommu virtual address width

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 10/11/2022 3:08 PM, Michael Piszczek wrote:
> Add code to read the virtual address width for AMD processors.
> 
> Signed-off-by: Michael Piszczek <mpiszczek@ddn.com>
> ---
>   drivers/bus/pci/linux/pci.c | 48 ++++++++++++++++++++++++-------------
>   1 file changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> index ebd1395502..cdac634e6c 100644
> --- a/drivers/bus/pci/linux/pci.c
> +++ b/drivers/bus/pci/linux/pci.c
> @@ -480,15 +480,18 @@ rte_pci_scan(void)
>   }
>   
>   #if defined(RTE_ARCH_X86)
> +
>   bool
>   pci_device_iommu_support_va(const struct rte_pci_device *dev)
>   {
>   #define VTD_CAP_MGAW_SHIFT	16
>   #define VTD_CAP_MGAW_MASK	(0x3fULL << VTD_CAP_MGAW_SHIFT)
> +#define RD_AMD_CAP_VASIZE_SHIFT 15
> +#define RD_AMD_CAP_VASIZE_MASK  (0x7F << RD_AMD_CAP_VASIZE_SHIFT)
>   	const struct rte_pci_addr *addr = &dev->addr;
>   	char filename[PATH_MAX];
>   	FILE *fp;
> -	uint64_t mgaw, vtd_cap_reg = 0;
> +	uint64_t mgaw = 0, cap_reg = 0;
>   
>   	snprintf(filename, sizeof(filename),
>   		 "%s/" PCI_PRI_FMT "/iommu/intel-iommu/cap",
> @@ -496,26 +499,39 @@ pci_device_iommu_support_va(const struct rte_pci_device *dev)
>   		 addr->function);
>   
>   	fp = fopen(filename, "r");
> -	if (fp == NULL) {
> -		/* We don't have an Intel IOMMU, assume VA supported */
> -		if (errno == ENOENT)
> -			return true;
> -
> -		RTE_LOG(ERR, EAL, "%s(): can't open %s: %s\n",
> -			__func__, filename, strerror(errno));
> -		return false;
> -	}
> +	if (fp != NULL) {
> +		/* We have an Intel IOMMU */
> +		if (fscanf(fp, "%" PRIx64, &cap_reg) != 1) {
> +			   RTE_LOG(ERR, EAL, "%s(): can't read %s\n", __func__, filename);
> +			fclose(fp);
> +			return false;
> +		}
>   
> -	/* We have an Intel IOMMU */
> -	if (fscanf(fp, "%" PRIx64, &vtd_cap_reg) != 1) {
> -		RTE_LOG(ERR, EAL, "%s(): can't read %s\n", __func__, filename);
>   		fclose(fp);
> -		return false;
> +		mgaw = ((cap_reg & VTD_CAP_MGAW_MASK) >> VTD_CAP_MGAW_SHIFT) + 1;
>   	}
> +	else {
> +		snprintf(filename, sizeof(filename),
> +			 "%s/" PCI_PRI_FMT "/iommu/amd-iommu/cap",
> +			  rte_pci_get_sysfs_path(), addr->domain, addr->bus, addr->devid,
> +			  addr->function);
> +


As suggested in v3, instead of first trying to open intel file later amd 
file, what do you think to use glob() function to detect the file?

> +		fp = fopen(filename, "r");
> +		if (fp != NULL) {
> +			/* We have an Amd IOMMU */
> +			if (fscanf(fp, "%" PRIx64, &cap_reg) != 1) {
> +				   RTE_LOG(ERR, EAL, "%s(): can't read %s\n", __func__, filename);
> +				fclose(fp);
> +				return false;
> +			}
>   
> -	fclose(fp);
> +			fclose(fp);
> +			mgaw = ((cap_reg & RD_AMD_CAP_VASIZE_MASK) >> RD_AMD_CAP_VASIZE_SHIFT) + 1;
> +		}
> +	}
>   
> -	mgaw = ((vtd_cap_reg & VTD_CAP_MGAW_MASK) >> VTD_CAP_MGAW_SHIFT) + 1;
> +	if (mgaw == 0)
> +		return false;
>   
>   	/*
>   	 * Assuming there is no limitation by now. We can not know at this point