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 <maciej.wieczor-retman@xxxxxxxxx>
---
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
