From: Paolo Bonzini <pbonzini@redhat.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>, linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
Thomas Gleixner <tglx@linutronix.de>,
Sean Christopherson <seanjc@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Andi Kleen <ak@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
Uros Bizjak <ubizjak@gmail.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: Re: [PATCH 0/4] x86: Don't invoke asm_exc_nmi() on the kernel stack
Date: Fri, 30 Apr 2021 09:14:23 +0200 [thread overview]
Message-ID: <228d8b10-84cb-4dd2-8810-3c94bc3ae07b@redhat.com> (raw)
In-Reply-To: <20210426230949.3561-1-jiangshanlai@gmail.com>
On 27/04/21 01:09, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
>
> In VMX, the NMI handler needs to be invoked after NMI VM-Exit.
>
> Before the commit 1a5488ef0dcf6 ("KVM: VMX: Invoke NMI handler via
> indirect call instead of INTn"), the work is done by INTn ("int $2").
>
> But INTn microcode is relatively expensive, so the commit reworked
> NMI VM-Exit handling to invoke the kernel handler by function call.
> And INTn doesn't set the NMI blocked flag required by the linux kernel
> NMI entry. So moving away from INTn are very reasonable.
>
> Yet some details were missed. After the said commit applied, the NMI
> entry pointer is fetched from the IDT table and called from the kernel
> stack. But the NMI entry pointer installed on the IDT table is
> asm_exc_nmi() which expects to be invoked on the IST stack by the ISA.
> And it relies on the "NMI executing" variable on the IST stack to work
> correctly. When it is unexpectedly called from the kernel stack, the
> RSP-located "NMI executing" variable is also on the kernel stack and
> is "uninitialized" and can cause the NMI entry to run in the wrong way.
>
> During fixing the problem for KVM, I found that there might be the same
> problem for early booting stage where the IST is not set up. asm_exc_nmi()
> is not allowed to be used in this stage for the same reason about
> the RSP-located "NMI executing" variable.
>
> For both cases, we should use asm_noist_exc_nmi() which is introduced
> in the patch 1 via renaming from an existing asm_xenpv_exc_nmi() and
> which is safe on the kernel stack.
>
> https://lore.kernel.org/lkml/20200915191505.10355-3-sean.j.christopherson@intel.com/
For the KVM part,
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Thanks,
Paolo
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>
> Cc: Jim Mattson <jmattson@google.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: kvm@vger.kernel.org
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Uros Bizjak <ubizjak@gmail.com>
> Cc: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
>
> Lai Jiangshan (4):
> x86/xen/entry: Rename xenpv_exc_nmi to noist_exc_nmi
> x86/entry: Use asm_noist_exc_nmi() for NMI in early booting stage
> KVM/VMX: Invoke NMI non-IST entry instead of IST entry
> KVM/VMX: fold handle_interrupt_nmi_irqoff() into its solo caller
>
> arch/x86/include/asm/idtentry.h | 4 +---
> arch/x86/kernel/idt.c | 8 +++++++-
> arch/x86/kernel/nmi.c | 12 ++++++++++++
> arch/x86/kvm/vmx/vmx.c | 27 ++++++++++++++-------------
> arch/x86/xen/enlighten_pv.c | 9 +++------
> arch/x86/xen/xen-asm.S | 2 +-
> 6 files changed, 38 insertions(+), 24 deletions(-)
>
next prev parent reply other threads:[~2021-04-30 7:14 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-26 23:09 [PATCH 0/4] x86: Don't invoke asm_exc_nmi() on the kernel stack Lai Jiangshan
2021-04-26 23:09 ` [PATCH 1/4] x86/xen/entry: Rename xenpv_exc_nmi to noist_exc_nmi Lai Jiangshan
2021-04-28 21:27 ` Steven Rostedt
2021-04-30 7:15 ` Paolo Bonzini
2021-04-30 12:05 ` Steven Rostedt
2021-05-03 19:05 ` Thomas Gleixner
2021-05-03 19:41 ` Thomas Gleixner
2021-05-10 7:59 ` Juergen Gross
2021-04-26 23:09 ` [PATCH 2/4] x86/entry: Use asm_noist_exc_nmi() for NMI in early booting stage Lai Jiangshan
2021-04-28 21:30 ` Steven Rostedt
2021-05-03 20:13 ` Thomas Gleixner
2021-05-03 20:24 ` Thomas Gleixner
2021-05-03 21:45 ` Thomas Gleixner
2021-05-04 12:43 ` Thomas Gleixner
2021-05-04 19:50 ` [PATCH] KVM/VMX: Invoke NMI non-IST entry instead of IST entry Thomas Gleixner
2021-05-04 21:05 ` Maxim Levitsky
2021-05-04 21:12 ` Paolo Bonzini
2021-05-04 21:21 ` Sean Christopherson
2021-05-04 21:23 ` Andy Lutomirski
2021-05-04 21:25 ` Paolo Bonzini
2021-05-04 21:51 ` Sean Christopherson
2021-05-04 21:56 ` Paolo Bonzini
2021-05-05 0:00 ` Thomas Gleixner
2021-05-05 15:44 ` Lai Jiangshan
2021-05-05 1:07 ` Lai Jiangshan
2021-05-05 1:11 ` Andy Lutomirski
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Lai Jiangshan
2021-04-26 23:09 ` [PATCH 3/4] " Lai Jiangshan
2021-04-30 2:46 ` Lai Jiangshan
2021-05-03 19:37 ` Thomas Gleixner
2021-05-03 20:02 ` Thomas Gleixner
2021-05-04 8:10 ` Paolo Bonzini
2021-04-26 23:09 ` [PATCH 4/4] KVM/VMX: Fold handle_interrupt_nmi_irqoff() into its solo caller Lai Jiangshan
2021-04-30 9:03 ` Thomas Gleixner
2021-04-30 9:06 ` Paolo Bonzini
2021-04-30 23:28 ` Thomas Gleixner
2021-04-30 7:14 ` Paolo Bonzini [this message]
2021-05-03 14:36 ` [PATCH 0/4] x86: Don't invoke asm_exc_nmi() on the kernel stack Thomas Gleixner
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