[PATCH 6/6] x86/sev-es: Leave NMI-mode before sending signals
From: Joerg Roedel <joro@8bytes.org>
Date: 2021-05-12 07:55:28
Also in:
kvm, linux-coco, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Joerg Roedel <redacted>
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 <redacted>
---
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
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization