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
WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org> To: x86@kernel.org, Hyunwook Baek <baekhw@google.com> Cc: kvm@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Dave Hansen <dave.hansen@linux.intel.com>, virtualization@lists.linux-foundation.org, Arvind Sankar <nivedita@alum.mit.edu>, hpa@zytor.com, Jiri Slaby <jslaby@suse.cz>, Joerg Roedel <joro@8bytes.org>, David Rientjes <rientjes@google.com>, Martin Radev <martin.b.radev@gmail.com>, Tom Lendacky <thomas.lendacky@amd.com>, Joerg Roedel <jroedel@suse.de>, Kees Cook <keescook@chromium.org>, Cfir Cohen <cfir@google.com>, linux-coco@lists.linux.dev, Andy Lutomirski <luto@kernel.org>, Dan Williams <dan.j.williams@intel.com>, Juergen Gross <jgross@suse.com>, Mike Stunes <mstunes@vmware.com>, Sean Christopherson <seanjc@google.com>, linux-kernel@vger.kernel.org, Masami Hiramatsu <mhiramat@kernel.org>, Erdem Aktas <erdemaktas@google.com> 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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-05-12 7:55 UTC|newest] Thread overview: 51+ 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 ` 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 ` 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 7:54 ` Joerg Roedel 2021-05-12 17:31 ` Sean Christopherson 2021-05-19 13:16 ` Joerg Roedel 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 7:54 ` Joerg Roedel 2021-05-12 8:04 ` David Laight 2021-05-12 8:04 ` David Laight 2021-05-12 8:04 ` David Laight 2021-05-12 8:16 ` Juergen Gross 2021-05-12 8:16 ` Juergen Gross via Virtualization 2021-05-12 8:16 ` Juergen Gross 2021-05-12 8:50 ` 'Joerg Roedel' 2021-05-12 8:50 ` 'Joerg Roedel' 2021-05-12 8:50 ` 'Joerg Roedel' 2021-05-12 8:58 ` Juergen Gross 2021-05-12 8:58 ` Juergen Gross via Virtualization 2021-05-12 8:58 ` Juergen Gross 2021-05-12 9:31 ` David Laight 2021-05-12 9:31 ` David Laight 2021-05-12 9:31 ` David Laight 2021-05-12 9:32 ` Joerg Roedel 2021-05-12 9:32 ` Joerg Roedel 2021-05-12 9:32 ` Joerg Roedel 2021-05-19 11:33 ` 'Joerg Roedel' 2021-05-19 11:33 ` 'Joerg Roedel' 2021-05-19 11:33 ` 'Joerg Roedel' 2021-05-12 8:37 ` 'Joerg Roedel' 2021-05-12 8:37 ` 'Joerg Roedel' 2021-05-12 8:37 ` 'Joerg Roedel' 2021-05-12 15:59 ` Dave Hansen 2021-05-12 15:59 ` Dave Hansen 2021-05-12 15:59 ` Dave Hansen 2021-05-12 15:57 ` Dave Hansen 2021-05-12 15:57 ` Dave Hansen 2021-05-12 16:00 ` Joerg Roedel 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 7:54 ` Joerg Roedel 2021-05-12 17:38 ` Sean Christopherson 2021-05-19 12:22 ` Joerg Roedel 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 2021-05-12 7:54 ` Joerg Roedel [this message] 2021-05-12 7:54 ` [PATCH 6/6] x86/sev-es: Leave NMI-mode before sending signals Joerg Roedel
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