Re: [PATCH] x86/boot: Use EFI setup data if provided

[Kairui Song]

On Mon, Mar 25, 2019 at 2:20 PM Dave Young <dyoung@xxxxxxxxxx> wrote:
>
> On 03/25/19 at 02:01pm, Dave Young wrote:
> > On 03/25/19 at 12:27am, Junichi Nomura wrote:
> > > On Fri, Mar 22, 2019 at 04:23:28PM +0100, Borislav Petkov wrote:
> > > > On Fri, Mar 22, 2019 at 11:03:43AM +0000, Junichi Nomura wrote:
> > > > > Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> > > > > boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> > > > > in the early parsing code tries to search RSDP from EFI table but
> > > > > whose address is virtual.
> > > > >
> > > > > Since kexec(1) provides physical address of config_table via boot_params,
> > > > > efi_get_rsdp_addr() should look for setup_data in the same way as
> > > > > efi_systab_init() in arch/x86/platform/efi/efi.c does.
> > > >
> > > > If the kexec kernel should continue to use efi_systab_init() then you
> > > > should make efi_get_rsdp_addr() exit early in the kexec-ed kernel.
> > >
> > > I'm not sure which way kexec devel is going. Added kexec list.
> > > Here is the version that exits early in efi_get_rsdp_addr().
> > >
> > > [PATCH] x86/boot: Don't try to search RSDP from EFI when kexec-booted
> > >
> > > Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> > > boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> > > in the early parsing code tries to search RSDP from EFI table but
> > > whose address is virtual.
> > >
> > > Normally kexec(1) provides physical address of config_table via boot_params
> > > and EFI code uses that during initialization.
> > > For the early boot code, we just exit efi_get_rsdp_addr() early if the kernel
> > > is booted by kexec.
> > >
> > > Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
> > > Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> > > Cc: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> > > Cc: Borislav Petkov <bp@xxxxxxx>
> > >
> > > diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> > > index 0ef4ad5..1cefc43 100644
> > > --- a/arch/x86/boot/compressed/acpi.c
> > > +++ b/arch/x86/boot/compressed/acpi.c
> > > @@ -44,6 +44,24 @@ static acpi_physical_address get_acpi_rsdp(void)
> > >     return addr;
> > >  }
> > >
> > > +static bool is_kexec_booted(void)
> > > +{
> > > +   struct setup_data *data;
> > > +
> > > +   /*
> > > +    * kexec-tools provides EFI setup data so that kexec-ed kernel
> > > +    * can find proper tables.
> > > +    */
> > > +   data = (struct setup_data *) boot_params->hdr.setup_data;
> > > +   while (data) {
> > > +           if (data->type == SETUP_EFI)
> > > +                   return true;
> > > +           data = (struct setup_data *) data->next;
> > > +   }
> > > +
> > > +   return false;
> > > +}
> > > +
> > >  /* Search EFI system tables for RSDP. */
> > >  static acpi_physical_address efi_get_rsdp_addr(void)
> > >  {
> > > @@ -57,6 +75,10 @@ static acpi_physical_address efi_get_rsdp_addr(void)
> > >     int size, i;
> > >     char *sig;
> > >
> > > +   /* If the system is kexec-booted, poking EFI systab may not work. */
> > > +   if (is_kexec_booted())
> > > +           return 0;
> > > +
> > >     ei = &boot_params->efi_info;
> > >     sig = (char *)&ei->efi_loader_signature;
> > >
> > >
> > > _______________________________________________
> > > kexec mailing list
> > > kexec@xxxxxxxxxxxxxxxxxxx
> > > http://lists.infradead.org/mailman/listinfo/kexec
> >
> > Good catch, this way looks good to me.  But the function
> > is_kexec_booted can be compiled when #ifdef CONFIG_EFI
> >
> > Otherwise:
> >
> > Acked-by: Dave Young <dyoung@xxxxxxxxxx>
> >
>
> Hold on, I replied too quick.  One question is does the above patch
> passed your test?   It can workaround and skip the wrong phys addr
> issue, but the acpi early parsing still fails because efi_get_rsdp_addr
> return 0?
>
> If this is the case you may need go with your old patch.
>
> I think normally people do not see this bug, because kernel will set the
> rsdp in boot_params->acpi_rsdp_addr.  Maybe you are testing with
> different kernel versions, eg.
>
> old kernel kexec to new kernel.
>
> And the old kernel does not set boot_params->acpi_rsdp_addr
>
> Is this correct?
>
> Thanks
> Dave

Hi Dave, actually only kexec_file_load will always set the
boot_params->acpi_rsdp_addr. Can't guarantee how user space tools will
prepare the boot_prams if kexec_load is used, so it's should very
likely to happen.

And for the patch, I also think the first patch looks better, if we
just return 0 early in efi_get_rsdp_addr aren't we still failing to
parse the rsdp in early code?

-- 
Best Regards,
Kairui Song