[PATCH] selftests/powerpc/spectre_v2: Return skip code when miss_percent is high

[PATCH] selftests/powerpc/spectre_v2: Return skip code when miss_percent is high

[Thadeu Lima de Souza Cascardo]

A mis-match between reported and actual mitigation is not restricted to the
Vulnerable case. The guest might also report the mitigation as "Software
count cache flush" and the host will still mitigate with branch cache
disabled.

So, instead of skipping depending on the detected mitigation, simply skip
whenever the detected miss_percent is the expected one for a fully
mitigated system, that is, above 95%.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---
 tools/testing/selftests/powerpc/security/spectre_v2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/powerpc/security/spectre_v2.c b/tools/testing/selftests/powerpc/security/spectre_v2.c
index adc2b7294e5f..83647b8277e7 100644
--- a/tools/testing/selftests/powerpc/security/spectre_v2.c
+++ b/tools/testing/selftests/powerpc/security/spectre_v2.c
@@ -193,7 +193,7 @@ int spectre_v2_test(void)
 			 * We are not vulnerable and reporting otherwise, so
 			 * missing such a mismatch is safe.
 			 */
-			if (state == VULNERABLE)
+			if (miss_percent > 95)
 				return 4;
 
 			return 1;
-- 
2.32.0

Re: [PATCH] selftests/powerpc/spectre_v2: Return skip code when miss_percent is high

[Michael Ellerman]

On Tue, 7 Dec 2021 10:05:57 -0300, Thadeu Lima de Souza Cascardo wrote:
> A mis-match between reported and actual mitigation is not restricted to the
> Vulnerable case. The guest might also report the mitigation as "Software
> count cache flush" and the host will still mitigate with branch cache
> disabled.
> 
> So, instead of skipping depending on the detected mitigation, simply skip
> whenever the detected miss_percent is the expected one for a fully
> mitigated system, that is, above 95%.
> 
> [...]

Applied to powerpc/next.

[1/1] selftests/powerpc/spectre_v2: Return skip code when miss_percent is high
      https://git.kernel.org/powerpc/c/3c42e9542050d49610077e083c7c3f5fd5e26820

cheers