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Date:   Thu, 17 Jan 2019 16:53:16 +0800
From:   Dave Young <dyoung@redhat.com>
To:     Kairui Song <kasong@redhat.com>
Cc:     Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org,
        tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        x86@kernel.org, Baoquan He <bhe@redhat.com>,
        kexec@lists.infradead.org, akpm@linux-foundation.org,
        robert.moore@intel.com, erik.schmauss@intel.com,
        rafael.j.wysocki@intel.com, Len Brown <lenb@kernel.org>,
        Chao Fan <fanc.fnst@cn.fujitsu.com>, linux-acpi@vger.kernel.org
Subject: Re: [PATCH v2 2/2] x86, kexec_file_load: make it work with
 efi=noruntime or efi=old_map
Message-ID: <20190117085316.GA17940@dhcp-128-65.nay.redhat.com>
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On 01/17/19 at 03:41pm, Kairui Song wrote:
> On Wed, Jan 16, 2019 at 5:46 PM Borislav Petkov <bp@alien8.de> wrote:
> >
> > On Wed, Jan 16, 2019 at 03:08:42PM +0800, Kairui Song wrote:
> > > I didn't see a way to reuse things in that patch series, situation is
> > > different, in that patch it needs to get RSDP in very early boot stage
> > > so it did everything from scratch, in this patch kexec_file_load need
> > > to get RSDP too, but everything is well setup so things are a lot
> > > easier, just read from current boot_prams, efi and fallback to
> > > acpi_find_root_pointer should be good.
> >
> > No no. Early code should find out that venerable RSDP thing once and
> > will save it somewhere for further use. No gazillion parsings of it.
> > Just once and share it with the rest of the code that needs it.
> >
> 
> How about we refill the boot_params.acpi_rsdp_addr if it is not valid
> in early code, so it could be used as a reliable RSDP address source?
> That should make things easier.
> 
> But if early code should parse it and store it should be done in
> Chao's patch, or I can post another patch to do it if Chao's patch is
> merged.
> 
> For now I think good to have something like this in this patch series
> to always keep storing acpi_rsdp in late code,
> acpi_os_get_root_pointer_late (maybe comeup with a better name later)
> could be used anytime to get RSDP and no extra parsing:
> 
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -180,8 +180,8 @@ void acpi_os_vprintf(const char *fmt, va_list args)
>  #endif
>  }
> 
> -#ifdef CONFIG_KEXEC
>  static unsigned long acpi_rsdp;
> +#ifdef CONFIG_KEXEC
>  static int __init setup_acpi_rsdp(char *arg)
>  {
>         return kstrtoul(arg, 16, &acpi_rsdp);
> @@ -189,28 +189,38 @@ static int __init setup_acpi_rsdp(char *arg)
>  early_param("acpi_rsdp", setup_acpi_rsdp);
>  #endif
> 
> +acpi_physical_address acpi_os_get_root_pointer_late(void) {
> +       return acpi_rsdp;
> +}
> +
>  acpi_physical_address __init acpi_os_get_root_pointer(void)
>  {
>         acpi_physical_address pa;
> 
> -#ifdef CONFIG_KEXEC
>         if (acpi_rsdp)
>                 return acpi_rsdp;
> -#endif
> +
>         pa = acpi_arch_get_root_pointer();
> -       if (pa)
> +       if (pa) {
> +               acpi_rsdp = pa;
>                 return pa;
> +       }
> 
>         if (efi_enabled(EFI_CONFIG_TABLES)) {
> -               if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
> +               if (efi.acpi20 != EFI_INVALID_TABLE_ADDR) {
> +                       acpi_rsdp = efi.acpi20;
>                         return efi.acpi20;
> -               if (efi.acpi != EFI_INVALID_TABLE_ADDR)
> +               }
> +               if (efi.acpi != EFI_INVALID_TABLE_ADDR) {
> +                       acpi_rsdp = efi.acpi;
>                         return efi.acpi;
> +               }
>                 pr_err(PREFIX "System description tables not found\n");
>         } else if (IS_ENABLED(CONFIG_ACPI_LEGACY_TABLES_LOOKUP)) {
>                 acpi_find_root_pointer(&pa);
>         }
> 
>  +       acpi_rsdp = pa;
>         return pa;
>  }
> 
> > --
> > Regards/Gruss,
> >     Boris.
> >
> > Good mailing practices for 400: avoid top-posting and trim the reply.
> --
> Best Regards,
> Kairui Song