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.
Check whether 5-level paging is enabled by trying to map a page in the high linear address space. Signed-off-by: Maciej Wieczor-Retman <[email protected]> --- Changelog v6: - Go back to using mmap() to check la57 status. Changelog v5: - Remove "cat" from system() call and use only "grep". Changelog v4: - Add this patch to the series. tools/testing/selftests/x86/lam.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c index 0ea4f6813930..1ce6cf322c3c 100644 --- a/tools/testing/selftests/x86/lam.c +++ b/tools/testing/selftests/x86/lam.c @@ -124,14 +124,18 @@ 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) +static inline int la57_enabled(void) { - unsigned int cpuinfo[4]; + int ret; + void *p; + + p = mmap((void *)HIGH_ADDR, PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); - __cpuid_count(0x7, 0, cpuinfo[0], cpuinfo[1], cpuinfo[2], cpuinfo[3]); + ret = p == MAP_FAILED ? 0 : 1; - return (cpuinfo[2] & (1 << 16)); + munmap(p, PAGE_SIZE); + return ret; } /* @@ -322,7 +326,7 @@ static int handle_mmap(struct testcases *test) flags, -1, 0); if (ptr == MAP_FAILED) { if (test->addr == HIGH_ADDR) - if (!cpu_has_la57()) + if (!la57_enabled()) return 3; /* unsupport LA57 */ return 1; } -- 2.47.1
