On 2024-11-27 at 14:11:38 +0200, Kirill A. Shutemov wrote:
>On Tue, Nov 26, 2024 at 02:34:48PM +0100, Maciej Wieczor-Retman wrote:
>> In current form cpu_has_la57() reports platform's support for LA57
>> through reading the output of cpuid. A much more useful information is
>> whether 5-level paging is actually enabled on the running system.
>>
>> Presence of the la57 flag in /proc/cpuinfo signifies that 5-level paging
>> was compiled into the kernel, is supported by the platform and wasn't
>> disabled by kernel command line argument.
>>
>> Use system() with cat and grep to figure out if la57 is enabled on the
>> running system.
>>
>> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
>> ---
>> Changelog v4:
>> - Add this patch to the series.
>>
>> tools/testing/selftests/x86/lam.c | 7 ++-----
>> 1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
>> index 0ea4f6813930..0ac805125ab2 100644
>> --- a/tools/testing/selftests/x86/lam.c
>> +++ b/tools/testing/selftests/x86/lam.c
>> @@ -124,14 +124,11 @@ static inline int cpu_has_lam(void)
>> return (cpuinfo[0] & (1 << 26));
>> }
>>
>> -/* Check 5-level page table feature in CPUID.(EAX=07H, ECX=00H):ECX.[bit 16] */
>> static inline int cpu_has_la57(void)
>> {
>> - unsigned int cpuinfo[4];
>> -
>> - __cpuid_count(0x7, 0, cpuinfo[0], cpuinfo[1], cpuinfo[2], cpuinfo[3]);
>> + int ret = !!system("cat /proc/cpuinfo | grep -wq la57\n");
>
>Heh. grep can read files on its own :P
>
> return !system("grep -wq la57 /proc/cpuinfo");
>
Oh, thanks, missed this :)
I'll resend after fixing it.
>>
>> - return (cpuinfo[2] & (1 << 16));
>> + return !ret;
>> }
>>
>> /*
>> --
>> 2.47.1
>>
>
>--
> Kiryl Shutsemau / Kirill A. Shutemov
--
Kind regards
Maciej Wieczór-Retman
