From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794419042; b=R5Tr9xTUzYAb2KmqeiiyDDoIgz+nTcxCfA9ZFmi+R4lftZpWbQucLAQZgDVIL5Yx2kJF oMF8ksjePUmsCmmSnBi28ajhAXPa5VvjMQP8S8vVQi0LvLzXQkiWt0N1Dpamb8k1UpgSJ VubGT+G7BD+sCxXXr3eWh7XbEJeJRGUkAwCjEnxdRzo/q6EEZihlpJ+3i7k/qtTsfYmSV HjwxetpGmx1425usqGw2USRIIzqQ/48Tyk8URODFHYTinmrbHzFinz24RbMzX6RmwX4KX ZJhyhD7v7ooBUJVVif4FP6ElZwVYRNDysPr6BTayJ4lrme2qQidQmDQ/kMLZTW7TbtQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794419042; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=ueFX5CI3G7Wd955i94T1keyzaDfcOPXFWwjMvFohilc=; b=FEEuZcbUyGjgJle90QxTG63bD4YqcX/NPxH5Pr5VolTa9wbOD4PzucsAW7mp//2Apfz/ VoocVfIhGyQMryl8hQRAcy+JOnq0vENkyBckZQ2aFHIegraEpEm+HCNTmrgfZD9OI/KX2 UUE5pNfWxE+3WCuyftsWEVwdLOvuIfRsPvxPpmIgrgskM62DvfMqcnfIBTkrTHGYkyCAs tykJtxlVeyt1DYt2qfc/V2U+6vcQwmm22cTdLOltwfogv8YEZ5i/Xpl26NZitedM+RXy8 lkWN8AlKWccRaGbXwxwn4juKx/4wi/BicBRp0ErCpEiJFRbAfILHFy0HeJ4ye/lbISg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=M1QYGIAl; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8951F606A89B for ; Wed, 11 Nov 2026 17:44:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=M1QYGIAl Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7FF01F00A11; Wed, 11 Nov 2026 17:44:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794419042; bh=ueFX5CI3G7Wd955i94T1keyzaDfcOPXFWwjMvFohilc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=M1QYGIAleDPvw5We0FpEO2teVVVtAxba8KPU3bLJlO9eI+ztB/m5YIZj6Q66SBHJp zvDTjvi5LTkANdhu1ahGn+KOdoBKmoHWzbmKjAoPU2BTAjw/T3Seu3vPzHJZ/IJ8SB TEoss1Syl2SRyI7rOdoOaXSvCwujoGrUAxKNMsFaZSy7v6p/xzrkSVHx/2MU8hRf+V YJ5Vhxh6Emid+ZobRFHHgN7VjplYI1ZXNUkwWQ5c075yqmoVgZxWmhq603Rxjqvj2q FIuai4D50lvgWuBrsEE5qhxD3iBXqJxVDl9lOUUk6mpVm8nj9TNeLnK8BUGgEZ7/NB CfYyy4pcpF3xQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Marc Zyngier , Fuad Tabba , Sasha Levin Subject: [PATCH 5.15.y] KVM: arm64: Turn vcpu->arch.pause into a counter Date: Wed, 11 Nov 2026 12:44:00 -0500 Message-ID: <20261111174337.3633257-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107060655-failed-5.15-e64309198eda@kernel.org> References: <20261107060655-failed-5.15-e64309198eda@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Marc Zyngier [ Upstream commit e64309198eda29415a95113def92aa40196cd422 ] We have situations where we can call kvm_arm_halt_guest() without holding config_lock, which means that halt and resume can overlap in funny ways when called from separate contexts, and result in situations where a vcpu is resumed while other parts of KVM assume it is halted. Consequences are left to the imagination of the reader. Fix this sorry situation by turning kvm_vcpu_arch::pause into an atomic counter, which makes the races described above harmless. Fixes: 3b92830ad41b2 ("KVM: arm/arm64: implement kvm_arm_[halt,resume]_guest") Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20261015100539.1011760-5-maz@kernel.org Signed-off-by: Marc Zyngier [ sashal: Inlined vcpu_can_run() checks using power_off while retaining vcpu_req_sleep() and rcuwait_wake_up(). ] Signed-off-by: Sasha Levin --- arch/arm64/include/asm/kvm_host.h | 2 +- arch/arm64/kvm/arm.c | 13 +++++++------ 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 6d7b6b5d076d4..660d8ef766796 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -368,7 +368,7 @@ struct kvm_vcpu_arch { bool power_off; /* Don't run the guest (internal implementation need) */ - bool pause; + atomic_t pause; /* Cache some mmu pages needed inside spinlock regions */ struct kvm_mmu_memory_cache mmu_page_cache; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 6bff7fd323872..0ef2b4a2b5f1a 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -336,6 +336,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) kvm_arm_pvtime_vcpu_init(&vcpu->arch); vcpu->arch.hw_mmu = &vcpu->kvm->arch.mmu; + atomic_set(&vcpu->arch.pause, 0); err = kvm_vgic_vcpu_init(vcpu); if (err) @@ -496,7 +497,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) { bool irq_lines = *vcpu_hcr(v) & (HCR_VI | HCR_VF); return ((irq_lines || kvm_vgic_vcpu_pending_irq(v)) - && !v->arch.power_off && !v->arch.pause); + && !v->arch.power_off && !atomic_read(&v->arch.pause)); } bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) @@ -636,7 +637,7 @@ void kvm_arm_halt_guest(struct kvm *kvm) struct kvm_vcpu *vcpu; kvm_for_each_vcpu(i, vcpu, kvm) - vcpu->arch.pause = true; + atomic_inc(&vcpu->arch.pause); kvm_make_all_cpus_request(kvm, KVM_REQ_SLEEP); } @@ -646,8 +647,8 @@ void kvm_arm_resume_guest(struct kvm *kvm) struct kvm_vcpu *vcpu; kvm_for_each_vcpu(i, vcpu, kvm) { - vcpu->arch.pause = false; - rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu)); + if (atomic_dec_and_test(&vcpu->arch.pause)) + rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu)); } } @@ -656,10 +657,10 @@ static void vcpu_req_sleep(struct kvm_vcpu *vcpu) struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu); rcuwait_wait_event(wait, - (!vcpu->arch.power_off) &&(!vcpu->arch.pause), + !vcpu->arch.power_off && !atomic_read(&vcpu->arch.pause), TASK_INTERRUPTIBLE); - if (vcpu->arch.power_off || vcpu->arch.pause) { + if (vcpu->arch.power_off || atomic_read(&vcpu->arch.pause)) { /* Awaken to handle a signal, request we sleep again later. */ kvm_make_request(KVM_REQ_SLEEP, vcpu); } -- 2.53.0