linux-kernel - [PATCH v3 09/14] x86/svm: Deflake svm_tsc_scale

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Message-ID: <20251110232642.633672-10-yosry.ahmed@linux.dev>
Date: Mon, 10 Nov 2025 23:26:37 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Kevin Cheng <chengkev@...gle.com>,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH v3 09/14] x86/svm: Deflake svm_tsc_scale_test

On an AMT Turin (EPYC Zen 5), svm_tsc_scale_test flakes on the last test
case with 0.0001 TSC scaling ratio, even with the 24-bit shift for
stability. On failure, the actual value is 49 instead of the expected
50.

Use a higher scaling ratio, 0.001, which makes the test pass
consistently.

Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 x86/svm_tests.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index 61ab63db462dc..1e7556a37adec 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -943,7 +943,7 @@ static void svm_tsc_scale_test(void)
 	}
 
 	svm_tsc_scale_run_testcase(50, 255, rdrand());
-	svm_tsc_scale_run_testcase(50, 0.0001, rdrand());
+	svm_tsc_scale_run_testcase(50, 0.001, rdrand());
 }
 
 static void latency_prepare(struct svm_test *test)
-- 
2.51.2.1041.gc1ab5b90ca-goog