From: Yury Norov <yury.norov@gmail.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Yury Norov <yury.norov@gmail.com>, Zheyun Shen <szy0127@sjtu.edu.cn>
Subject: [PATCH 2/2] KVM: SVM: drop useless cpumask_test_cpu() in pre_sev_run()
Date: Mon, 11 Aug 2025 16:30:40 -0400 [thread overview]
Message-ID: <20250811203041.61622-3-yury.norov@gmail.com> (raw)
In-Reply-To: <20250811203041.61622-1-yury.norov@gmail.com>
Testing cpumask for a CPU to be cleared just before setting the exact
same CPU is useless because the end result is always the same: CPU is
set.
While there, switch CPU setter to a non-atomic version. Atomicity is
useless here because sev_writeback_caches() ends up with a plain
for_each_cpu() loop in smp_call_function_many_cond(), which is not
atomic by nature.
Fixes: 6f38f8c57464 ("KVM: SVM: Flush cache only on CPUs running SEV guest")
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
arch/x86/kvm/svm/sev.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 49d7557de8bc..8170674d39c1 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3498,8 +3498,7 @@ int pre_sev_run(struct vcpu_svm *svm, int cpu)
* have encrypted, dirty data in the cache, and flush caches only for
* CPUs that have entered the guest.
*/
- if (!cpumask_test_cpu(cpu, to_kvm_sev_info(kvm)->have_run_cpus))
- cpumask_set_cpu(cpu, to_kvm_sev_info(kvm)->have_run_cpus);
+ __cpumask_set_cpu(cpu, to_kvm_sev_info(kvm)->have_run_cpus);
/* Assign the asid allocated with this SEV guest */
svm->asid = asid;
--
2.43.0
next prev parent reply other threads:[~2025-08-11 20:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-11 20:30 [PATCH 0/2] KVM: SVM: fixes for SEV Yury Norov
2025-08-11 20:30 ` [PATCH 1/2] KVM: SVM: don't check have_run_cpus in sev_writeback_caches() Yury Norov
2025-08-11 20:50 ` Sean Christopherson
2025-08-11 21:05 ` Yury Norov
2025-08-11 21:21 ` Sean Christopherson
2025-08-11 21:31 ` Yury Norov
2025-08-11 20:30 ` Yury Norov [this message]
2025-08-11 20:45 ` [PATCH 2/2] KVM: SVM: drop useless cpumask_test_cpu() in pre_sev_run() Sean Christopherson
2025-08-11 21:28 ` Yury Norov
2025-08-11 22:04 ` Sean Christopherson
2025-08-14 0:42 ` Yury Norov
2025-08-19 23:11 ` [PATCH 0/2] KVM: SVM: fixes for SEV Sean Christopherson
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