From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1CF71F76C6; Tue, 3 Dec 2024 15:58:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733241518; cv=none; b=YddvUJ+ACJ5+le4O6y9Qdlur0Ru+W7NLnswoQai7gKf4jo+PhVy4B92qL815g0wXDpd4ZbTsyVnjnCc4uMWmYzpvWMBzCjtUryx3oeXwWBLWuN3FdCAOEDhrTlTU/cIws+kotWrgFv1tpgBVHM+7NjLrnvXK1/UeZrGpZdWIxPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733241518; c=relaxed/simple; bh=pRwoXjSCY7zWlM2Ex4QzqElNfSwwy5LjJ1+1GtJSyeU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=n1AVGTKfRhEIzYpaEfmZWWdmm2iU7rAGArjvxFfnSRV24Jq5ojOYyQhV0kK/PWFNSJYwCpVyjvGMi3b+RMHMhGZXexyM4J2exdbeC3I2Oa2bFu8OwHGtTLH0jbn7+V00vt2OSoA7khgUhBrmkq83/VopqEW6AdAto+/eEwXKfsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=F5mcZZsB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="F5mcZZsB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E31ACC4CECF; Tue, 3 Dec 2024 15:58:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733241518; bh=pRwoXjSCY7zWlM2Ex4QzqElNfSwwy5LjJ1+1GtJSyeU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=F5mcZZsBloWB3XrqusVrmE52ZCNyd5cto6OzcWnYO1vaZqC4qrQkrOPDt1wOwXjfp Sy7dep+gH5w1E1gGEioMsY3w15O452fxsu7XcsHAhQKhzt29D+jij8DoOlWJcC0dzr zQR79ak3hZukVpvgSjtL9xmRlPi6Z+NShbGEtGY8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gautam Menghani , Michael Ellerman , Sasha Levin Subject: [PATCH 6.12 440/826] KVM: PPC: Book3S HV: Avoid returning to nested hypervisor on pending doorbells Date: Tue, 3 Dec 2024 15:42:47 +0100 Message-ID: <20241203144800.925800267@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241203144743.428732212@linuxfoundation.org> References: <20241203144743.428732212@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gautam Menghani [ Upstream commit 26686db69917399fa30e3b3135360771e90f83ec ] Commit 6398326b9ba1 ("KVM: PPC: Book3S HV P9: Stop using vc->dpdes") dropped the use of vcore->dpdes for msgsndp / SMT emulation. Prior to that commit, the below code at L1 level (see [1] for terminology) was responsible for setting vc->dpdes for the respective L2 vCPU: if (!nested) { kvmppc_core_prepare_to_enter(vcpu); if (vcpu->arch.doorbell_request) { vc->dpdes = 1; smp_wmb(); vcpu->arch.doorbell_request = 0; } L1 then sent vc->dpdes to L0 via kvmhv_save_hv_regs(), and while servicing H_ENTER_NESTED at L0, the below condition at L0 level made sure to abort and go back to L1 if vcpu->arch.doorbell_request = 1 so that L1 sets vc->dpdes as per above if condition: } else if (vcpu->arch.pending_exceptions || vcpu->arch.doorbell_request || xive_interrupt_pending(vcpu)) { vcpu->arch.ret = RESUME_HOST; goto out; } This worked fine since vcpu->arch.doorbell_request was used more like a flag and vc->dpdes was used to pass around the doorbell state. But after Commit 6398326b9ba1 ("KVM: PPC: Book3S HV P9: Stop using vc->dpdes"), vcpu->arch.doorbell_request is the only variable used to pass around doorbell state. With the plumbing for handling doorbells for nested guests updated to use vcpu->arch.doorbell_request over vc->dpdes, the above "else if" stops doorbells from working correctly as L0 aborts execution of L2 and instead goes back to L1. Remove vcpu->arch.doorbell_request from the above "else if" condition as it is no longer needed for L0 to correctly handle the doorbell status while running L2. [1] Terminology 1. L0 : PowerNV linux running with HV privileges 2. L1 : Pseries KVM guest running on top of L0 2. L2 : Nested KVM guest running on top of L1 Fixes: 6398326b9ba1 ("KVM: PPC: Book3S HV P9: Stop using vc->dpdes") Signed-off-by: Gautam Menghani Signed-off-by: Michael Ellerman Link: https://patch.msgid.link/20241109063301.105289-4-gautam@linux.ibm.com Signed-off-by: Sasha Levin --- arch/powerpc/kvm/book3s_hv.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index b4c5295bdc31b..59f67a44621b7 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4921,7 +4921,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit, lpcr &= ~LPCR_MER; } } else if (vcpu->arch.pending_exceptions || - vcpu->arch.doorbell_request || xive_interrupt_pending(vcpu)) { vcpu->arch.ret = RESUME_HOST; goto out; -- 2.43.0