From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org, Hyunwook Baek <baekhw@google.com>
Cc: Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Jiri Slaby <jslaby@suse.cz>,
Dan Williams <dan.j.williams@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Juergen Gross <jgross@suse.com>,
Kees Cook <keescook@chromium.org>,
David Rientjes <rientjes@google.com>,
Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mike Stunes <mstunes@vmware.com>,
Sean Christopherson <seanjc@google.com>,
Martin Radev <martin.b.radev@gmail.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: [PATCH 6/6] x86/sev-es: Leave NMI-mode before sending signals
Date: Wed, 12 May 2021 09:54:45 +0200 [thread overview]
Message-ID: <20210512075445.18935-7-joro@8bytes.org> (raw)
In-Reply-To: <20210512075445.18935-1-joro@8bytes.org>
From: Joerg Roedel <jroedel@suse.de>
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 <jroedel@suse.de>
---
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 77155c4f07f5..79cbed2f28de 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1300,9 +1300,10 @@ 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
@@ -1352,13 +1353,19 @@ 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
@@ -1380,7 +1387,9 @@ 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
prev parent reply other threads:[~2021-05-12 7:55 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 7:54 [PATCH 0/6] x86/sev-es: Fixes for SEV-ES guest support Joerg Roedel
2021-05-12 7:54 ` [PATCH 1/6] x86/sev-es: Don't return NULL from sev_es_get_ghcb() Joerg Roedel
2021-05-12 7:54 ` [PATCH 2/6] x86/sev-es: Forward page-faults which happen during emulation Joerg Roedel
2021-05-12 17:31 ` Sean Christopherson
2021-05-19 13:16 ` Joerg Roedel
2021-05-12 7:54 ` [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user Joerg Roedel
2021-05-12 8:04 ` David Laight
2021-05-12 8:16 ` Juergen Gross
2021-05-12 8:50 ` 'Joerg Roedel'
2021-05-12 8:58 ` Juergen Gross
2021-05-12 9:31 ` David Laight
2021-05-12 9:32 ` Joerg Roedel
2021-05-19 11:33 ` 'Joerg Roedel'
2021-05-12 8:37 ` 'Joerg Roedel'
2021-05-12 15:59 ` Dave Hansen
2021-05-12 15:57 ` Dave Hansen
2021-05-12 16:00 ` Joerg Roedel
2021-05-12 7:54 ` [PATCH 4/6] Revert "x86/sev-es: Handle string port IO to kernel memory properly" Joerg Roedel
2021-05-12 17:38 ` Sean Christopherson
2021-05-19 12:22 ` Joerg Roedel
2021-05-12 7:54 ` [PATCH 5/6] x86/sev-es: Fix error message in runtime #VC handler Joerg Roedel
2021-05-12 7:54 ` Joerg Roedel [this message]
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