From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) (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 1BEDF6D00 for ; Wed, 19 May 2021 13:53:14 +0000 (UTC) Received: from cap.home.8bytes.org (p549ad305.dip0.t-ipconnect.de [84.154.211.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by theia.8bytes.org (Postfix) with ESMTPSA id CEA4C4CA; Wed, 19 May 2021 15:53:10 +0200 (CEST) From: Joerg Roedel To: x86@kernel.org, Hyunwook Baek Cc: Joerg Roedel , Joerg Roedel , hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Sean Christopherson , Martin Radev , Arvind Sankar , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: [PATCH v2 5/8] x86/sev-es: Leave NMI-mode before sending signals Date: Wed, 19 May 2021 15:52:48 +0200 Message-Id: <20210519135251.30093-6-joro@8bytes.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210519135251.30093-1-joro@8bytes.org> References: <20210519135251.30093-1-joro@8bytes.org> X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Joerg Roedel The error path in the runtime #VC handler sends a signal to kill the current task if the exception was raised from user-space. Some parts of the #VC handler run in NMI mode, because it is critical that it is not interrupted (except from an NMI) while the GHCB is in use. But sending signals in NMI-mode is actually broken and triggers lockdep warnings. On the other side, when the signal is sent, there is no reason for the handler to still be in NMI-mode, as the GHCB is not used anymore. Leave NMI-mode before entering the error path to get rid of the lockdep warnings. Fixes: 62441a1fb532 ("x86/sev-es: Correctly track IRQ states in runtime #VC handler") Signed-off-by: Joerg Roedel --- arch/x86/kernel/sev.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 4fd997bbf059..9a64030e74c0 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1343,9 +1343,10 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) return; } + instrumentation_begin(); + irq_state = irqentry_nmi_enter(regs); lockdep_assert_irqs_disabled(); - instrumentation_begin(); /* * This is invoked through an interrupt gate, so IRQs are disabled. The @@ -1395,13 +1396,19 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) BUG(); } -out: - instrumentation_end(); irqentry_nmi_exit(regs, irq_state); + instrumentation_end(); return; fail: + /* + * Leave NMI mode - the GHCB is not busy anymore and depending on where + * the #VC came from this code is about to either kill the task (when in + * task context) or kill the machine. + */ + irqentry_nmi_exit(regs, irq_state); + if (user_mode(regs)) { /* * Do not kill the machine if user-space triggered the @@ -1423,7 +1430,9 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) panic("Returned from Terminate-Request to Hypervisor\n"); } - goto out; + instrumentation_end(); + + return; } /* This handler runs on the #VC fall-back stack. It can cause further #VC exceptions */ -- 2.31.1