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");
>
> - return (cpuinfo[2] & (1 << 16));
> + return !ret;
> }
>
> /*
> --
> 2.47.1
>
--
Kiryl Shutsemau / Kirill A. Shutemov
