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From:   Pingfan Liu <kernelfans@gmail.com>
Date:   Thu, 26 Nov 2020 16:05:31 +0800
Message-ID: <CAFgQCTtUFxDZ0WE3wFZVXeHWe0OyB7R1WdVf45+USJ5CS=kiWA@mail.gmail.com>
Subject: Re: [PATCH 2/2] x86/machine_kexec: disable PMU before jumping to new kernel
To:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Omar Sandoval <osandov@fb.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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Sorry that I had made a misunderstanding of the code.

Nacked it

On Mon, Nov 23, 2020 at 1:37 PM Pingfan Liu <kernelfans@gmail.com> wrote:
>
> During jumping to the new kernel, on the crashed cpu, the memory mapping
> switches from an old one to an identity one. It had better disable PMU to
> suppress NMI, which can be delivered using the old mapping.
>
> Also on x86_64, idt_invalidate() to clear idt as on 32 bits.
>
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@kernel.org>
> To: x86@kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  arch/x86/kernel/machine_kexec_32.c | 1 +
>  arch/x86/kernel/machine_kexec_64.c | 3 +++
>  2 files changed, 4 insertions(+)
>
> diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
> index 64b00b0..72c6100 100644
> --- a/arch/x86/kernel/machine_kexec_32.c
> +++ b/arch/x86/kernel/machine_kexec_32.c
> @@ -191,6 +191,7 @@ void machine_kexec(struct kimage *image)
>         /* Interrupts aren't acceptable while we reboot */
>         local_irq_disable();
>         hw_breakpoint_disable();
> +       perf_pmu_disable_all();
>
>         if (image->preserve_context) {
>  #ifdef CONFIG_X86_IO_APIC
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index a29a44a..238893e 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -17,6 +17,7 @@
>  #include <linux/suspend.h>
>  #include <linux/vmalloc.h>
>  #include <linux/efi.h>
> +#include <linux/perf_event.h>
>
>  #include <asm/init.h>
>  #include <asm/tlbflush.h>
> @@ -338,6 +339,8 @@ void machine_kexec(struct kimage *image)
>         /* Interrupts aren't acceptable while we reboot */
>         local_irq_disable();
>         hw_breakpoint_disable();
> +       perf_pmu_disable_all();
> +       idt_invalidate(phys_to_virt(0));
>
>         if (image->preserve_context) {
>  #ifdef CONFIG_X86_IO_APIC
> --
> 2.7.5
>