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=1794063422; b=JC/elkjHk6xvtEhEalXKH6Ftxh+2i2mxYzfGAoRana7dtrlPJNHYp2uf8zOQYJy1Z2JL QIu4J/zXxDevAtXLXwfJ5uTg4Oo/UGvriU6zTJROpuzGHvvPwyPQHWwPiIdPFR6AxrGcn 8woF3UK0oUcB2VOFTguLXCAfR71E/IFNX5KH113tIVvJa83x36K2Y2hHdLfivqGCGVZZA Cd/M/Vq/yG44cwjsc07M8WJfEarnUp/yYwPkfIjzIKXHsvilP7hdMrBHlTrLfJDlLWC8M w9q/sMYL1KBozc480KMtzoKK2R44atqb0EGs8qyCdnuxnJS9fuYfs/1q9k44EY+ifIQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063422; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=Lx0PZzw4z2ODnaieWZaXwq0K2fr4oJ+1k134HytoX8k=; b=q1oT4uGP10KJdHtUPBCAgy1hOdwnQQpc/s8Ybh5YoqVV2dm37tcfEwR7eXgN9pB/xIOZ qjv89VAXvc/B765cIdhVt+7Y0F2bIc7CWajgbFzd/fpQLjb/vEfS/WLyQ14zTSdc5/UJR QfBXwDXY4fKIsEh5G7Jv4gxhEzQ3xihh79zlkeyCs2MoGBYTq0J7XdgkgljrbSPq9dG3E yHvxO61s9a5/2+4IdLTftcipAbBMpxCQ3Sov9u7CdBRmj1C2Xu/4A58wovwMTpdbuLkUk snh1GW/WLmepb6QeKWMp4cClb+6UdbdtJizRrytnpripC+RUIoXMdCeDmaNJwt3UWGw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=tCV91UXr; 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 A6010608360D; Sat, 7 Nov 2026 14:57:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=tCV91UXr Received: by smtp.kernel.org (Postfix) with ESMTPSA id 637841F008A2; Sat, 7 Nov 2026 14:57:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063421; bh=Lx0PZzw4z2ODnaieWZaXwq0K2fr4oJ+1k134HytoX8k=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=tCV91UXr3RxcihipRXA2ccvLNQSFzHStehIZnydUB+GQ+xjsJwT06yWFnLgmSbvP0 OxH9GZ9PBce4nRP4Gj3IR3k0As/tplZQxBsH3gc/hesYyOs1uK29Gah11vDPu9CI30 YP+fNSzKvkc7jARY1g0lWSfjn0DTRppDbyIBO7f0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fuad Tabba , Marc Zyngier , Sasha Levin Subject: [PATCH 6.18 587/869] KVM: arm64: Turn vcpu->arch.pause into a counter Date: Sat, 7 Nov 2026 08:54:29 -0500 Message-ID: <20261107134913.044756041@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Sasha Levin --- arch/arm64/include/asm/kvm_host.h | 7 +++---- arch/arm64/kvm/arm.c | 21 ++++++++++++--------- 2 files changed, 15 insertions(+), 13 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 419e37112a6f0..b7334f98deaac 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -833,11 +833,10 @@ struct kvm_vcpu_arch { /* * Don't run the guest (internal implementation need). * - * Contrary to the flags above, this is set/cleared outside of - * a vcpu context, and thus cannot be mixed with the flags - * themselves (or the flag accesses need to be made atomic). + * Contrary to the flags above, this is updated outside of + * a vcpu context, and thus cannot be mixed with the flags. */ - bool pause; + atomic_t pause; /* * We maintain more than a single set of debug registers to support diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index c8a8d9ce4b14e..4e0db01a528a8 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -500,6 +500,7 @@ 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); /* * This vCPU may have been created after mpidr_data was initialized. @@ -765,6 +766,11 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu, return ret; } +static bool vcpu_can_run(struct kvm_vcpu *vcpu) +{ + return !kvm_arm_vcpu_stopped(vcpu) && !atomic_read(&vcpu->arch.pause); +} + /** * kvm_arch_vcpu_runnable - determine if the vcpu can be scheduled * @v: The VCPU pointer @@ -780,8 +786,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) (kvm_timer_should_notify_user(v) || kvm_pmu_should_notify_user(v))); - return ((irq_lines || kvm_vgic_vcpu_pending_irq(v)) - && !kvm_arm_vcpu_stopped(v) && !v->arch.pause); + return ((irq_lines || kvm_vgic_vcpu_pending_irq(v)) && vcpu_can_run(v)); } bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) @@ -937,7 +942,7 @@ 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); } @@ -947,8 +952,8 @@ void kvm_arm_resume_guest(struct kvm *kvm) struct kvm_vcpu *vcpu; kvm_for_each_vcpu(i, vcpu, kvm) { - vcpu->arch.pause = false; - __kvm_vcpu_wake_up(vcpu); + if (atomic_dec_and_test(&vcpu->arch.pause)) + __kvm_vcpu_wake_up(vcpu); } } @@ -956,11 +961,9 @@ static void kvm_vcpu_sleep(struct kvm_vcpu *vcpu) { struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu); - rcuwait_wait_event(wait, - (!kvm_arm_vcpu_stopped(vcpu)) && (!vcpu->arch.pause), - TASK_INTERRUPTIBLE); + rcuwait_wait_event(wait, vcpu_can_run(vcpu), TASK_INTERRUPTIBLE); - if (kvm_arm_vcpu_stopped(vcpu) || vcpu->arch.pause) { + if (!vcpu_can_run(vcpu)) { /* Awaken to handle a signal, request we sleep again later. */ kvm_make_request(KVM_REQ_SLEEP, vcpu); } -- 2.53.0