Re: [PATCH v5] pci: read amd iommu virtual address width

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

On 10/24/2022 7:09 PM, Stephen Hemminger wrote:
> On Thu, 13 Oct 2022 20:16:02 +0200
> Michael Piszczek <mpiszczek@ddn.com> wrote:
> 
>> Add code to read the virtual address width for AMD processors.
>> Updated pci_device_iommu_support_va() to use glob to find iommu
>> capability files.
>>
>> Signed-off-by: Michael Piszczek <mpiszczek@ddn.com>
>> ---
>>   drivers/bus/pci/linux/pci.c | 58 ++++++++++++++++++++++---------------
>>   1 file changed, 35 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
>> index ebd1395502..291090ba7b 100644
>> --- a/drivers/bus/pci/linux/pci.c
>> +++ b/drivers/bus/pci/linux/pci.c
>> @@ -4,6 +4,7 @@
>>   
>>   #include <string.h>
>>   #include <dirent.h>
>> +#include <glob.h>
>>   
>>   #include <rte_log.h>
>>   #include <rte_pci.h>
>> @@ -480,42 +481,53 @@ 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 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)
>> +	int rc;
>>   	const struct rte_pci_addr *addr = &dev->addr;
>> -	char filename[PATH_MAX];
>> -	FILE *fp;
>> -	uint64_t mgaw, vtd_cap_reg = 0;
>> +	char pattern[PATH_MAX];
>> +	glob_t glob_results;
>> +	uint64_t mgaw = 0;
>>   
>> -	snprintf(filename, sizeof(filename),
>> -		 "%s/" PCI_PRI_FMT "/iommu/intel-iommu/cap",
>> +	snprintf(pattern, sizeof(pattern),
>> +		 "%s/" PCI_PRI_FMT "/iommu/*-iommu/cap",
>>   		 rte_pci_get_sysfs_path(), addr->domain, addr->bus, addr->devid,
>>   		 addr->function);
>>   
>> -	fp = fopen(filename, "r");
>> -	if (fp == NULL) {
>> -		/* We don't have an Intel IOMMU, assume VA supported */
>> -		if (errno == ENOENT)
>> -			return true;
>> +	rc = glob(pattern, 0, NULL, &glob_results);
>> +	if (rc != 0 && glob_results.gl_pathc == 1) {
>> +		const char *filename = glob_results.gl_pathv[0];
> 
> Why not use fnmatch() instead of glob()?
> Most of the places in DPDK use that to do this kind of matching.

Since glob() returns matching string, it can be useful to open the file.
Is there an advantage of fnmatch() against globe()?