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[195.150.55.226]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ba4520c93c7sm531722966b.27.2026.04.22.06.03.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 06:03:42 -0700 (PDT) From: Piotr Zarycki To: vkuznets@redhat.com Cc: kvm@vger.kernel.org, seanjc@google.com, pbonzini@redhat.com, shuah@kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Piotr Zarycki Subject: [PATCH v2] KVM: selftests: hyperv_tlb_flush: replace NOP loop with udelay() Date: Wed, 22 Apr 2026 15:03:07 +0200 Message-ID: <20260422130307.1171808-1-piotr.zarycki@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <87v7djgoji.fsf@redhat.com> References: <87v7djgoji.fsf@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace the open-coded NOP loop with udelay() which was added to KVM selftests in commit 6b878cbb87bf ("KVM: selftests: Add guest udelay() utility for x86"). The NOP loop is CPU speed dependent while udelay() provides a deterministic delay regardless of host CPU frequency. Signed-off-by: Piotr Zarycki --- .../testing/selftests/kvm/x86/hyperv_tlb_flush.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/tools/testing/selftests/kvm/x86/hyperv_tlb_flush.c b/tools/testing/selftests/kvm/x86/hyperv_tlb_flush.c index c542cc4762b1..4b7f089542c1 100644 --- a/tools/testing/selftests/kvm/x86/hyperv_tlb_flush.c +++ b/tools/testing/selftests/kvm/x86/hyperv_tlb_flush.c @@ -141,17 +141,6 @@ static void swap_two_test_pages(vm_paddr_t pte_gva1, vm_paddr_t pte_gva2) *(uint64_t *)pte_gva2 = tmp; } -/* - * TODO: replace the silly NOP loop with a proper udelay() implementation. - */ -static inline void do_delay(void) -{ - int i; - - for (i = 0; i < 1000000; i++) - asm volatile("nop"); -} - /* * Prepare to test: 'disable' workers by setting the expectation to '0', * clear hypercall input page and then swap two test pages. @@ -169,7 +158,7 @@ static inline void prepare_to_test(struct test_data *data) wmb(); /* Make sure workers have enough time to notice */ - do_delay(); + udelay(100); /* Swap test page mappings */ swap_two_test_pages(data->test_pages_pte[0], data->test_pages_pte[1]); @@ -189,7 +178,7 @@ static inline void post_test(struct test_data *data, u64 exp1, u64 exp2) set_expected_val((void *)data->test_pages, exp2, WORKER_VCPU_ID_2); /* Make sure workers have enough time to test */ - do_delay(); + udelay(100); } #define TESTVAL1 0x0101010101010101 -- 2.53.0