linux-kernel - Re: [PATCH v2 2/2] x86, kexec_file_load: make it work with efi=noruntime or efi=old

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Date:   Thu, 17 Jan 2019 15:49:59 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Kairui Song <kasong@...hat.com>
CC:     Borislav Petkov <bp@...en8.de>, <linux-kernel@...r.kernel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <x86@...nel.org>, Dave Young <dyoung@...hat.com>,
        Baoquan He <bhe@...hat.com>, <kexec@...ts.infradead.org>,
        <akpm@...ux-foundation.org>, <robert.moore@...el.com>,
        <erik.schmauss@...el.com>, <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v2 2/2] x86, kexec_file_load: make it work with
 efi=noruntime or efi=old_map

On Thu, Jan 17, 2019 at 03:41:13PM +0800, Kairui Song wrote:
>On Wed, Jan 16, 2019 at 5:46 PM Borislav Petkov <bp@...en8.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.

I think it's OK.
Try to read it, if get RSDP, use it.
If not, search in EFI/BIOS/... and refill the RSDP to
boot_params.acpi_rsdp_addr.
By the way, I search kernel code, I didn't find other code fill and
use it, only you(KEXEC) are trying to fill it.
If I miss something, please let me know.

Thanks,
Chao Fan

>
>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
>
>