Re: [PATCH] fix kdump kernel cannot find ACPI RSDP

[Chunjie Zhu]

> From: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> Date: Mon, 27 May 2024 12:52:19 +0200
> Subject: Re: [PATCH] fix kdump kernel cannot find ACPI RSDP
> To: Chunjie Zhu <chunjie.zhu@xxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>, linux-acpi@xxxxxxxxxxxxxxx, 
> 	linux-kernel@xxxxxxxxxxxxxxx
> 
> On Fri, May 24, 2024 at 11:43=E2=80=AFAM Chunjie Zhu <chunjie.zhu@xxxxxxxxx=
> > wrote:
> >
> > kexec/kdump must pass acpi_rsdp (physical address of ACPI RSDP table) to =
> the
> > crash kernel, especially in EFI case, otherwise, the crash kernel fails t=
> o
> > locate ACPI RSDP table. Consequently, ACPI init runs into error, and APIC
> > mmio read page fault happens, finally crash kernel gets stuck.
> 
> Fair enough.
> 
> So has this ever worked before?  Presumably it has, in which case it
> has regressed and so it would be prudent to say when it broke and why
> and explain why the proposed change is the right one to make.

The existing code works only if the kexec() system call (CONFIG_KEXEC) is
enabled, however, we can enter the kdump kernel by one of the following
methods,

	1. kexec_file system call (CONFIG_KEXEC_FILE)
	2. Xen-initiated crash

Instead of CONFIG_KEXEC, setup_acpi_rsdp should depend on CONFIG_KEXEC_CORE,
which should be enabled in any case where kernel is used as a kdump kernel.

> 
> > Signed-off-by: Chunjie Zhu <chunjie.zhu@xxxxxxxxx>
> > ---
> >  drivers/acpi/osl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > index f725813d0cce..39474468dba1 100644
> > --- a/drivers/acpi/osl.c
> > +++ b/drivers/acpi/osl.c
> > @@ -174,7 +174,7 @@ void acpi_os_vprintf(const char *fmt, va_list args)
> >  #endif
> >  }
> >
> > -#ifdef CONFIG_KEXEC
> > +#ifdef CONFIG_KEXEC_CORE
> >  static unsigned long acpi_rsdp;
> >  static int __init setup_acpi_rsdp(char *arg)
> >  {
> > @@ -187,7 +187,7 @@ acpi_physical_address __init acpi_os_get_root_pointer=
> (void)
> >  {
> >         acpi_physical_address pa;
> >
> > -#ifdef CONFIG_KEXEC
> > +#ifdef CONFIG_KEXEC_CORE
> >         /*
> >          * We may have been provided with an RSDP on the command line,
> >          * but if a malicious user has done so they may be pointing us
> > --
> > 2.34.1
> >
>