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

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Message-ID: <CACPcB9d0dKLPmZ=b++m5LYRjFUCFyLL3deDBcS4m3N-UWZ_Hyw@mail.gmail.com>
Date:   Thu, 17 Jan 2019 15:41:13 +0800
From:   Kairui Song <kasong@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     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>,
        Chao Fan <fanc.fnst@...fujitsu.com>
Subject: Re: [PATCH v2 2/2] x86, kexec_file_load: make it work with
 efi=noruntime or efi=old_map

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.

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