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SubjectRe: [PATCH] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernels
On 04/17/19 at 09:38am, Dave Young wrote:
> On 04/16/19 at 03:22pm, Borislav Petkov wrote:
> > On Tue, Apr 16, 2019 at 07:41:33PM +0800, Dave Young wrote:
> > > On 04/16/19 at 11:52am, Borislav Petkov wrote:
> > > > I'll queue the below in the next days if there are no more complaints:
> > >
> > > As for the kexec breakage, even with the V3 patch, kexec still hangs on
> > > a Lenovo T420 laptop. Kairui also reproduced the problem. So can we
> > > wait a few days see if we can make some progress to find the cause?
> >
> > How is applying this patch going to change anything?
> >
> > I was told that the breakage is there even without it...
>
> Without this patch, the bug happens in the efi_get_rsdp.. function, this
> patch tries to fix that by adding kexec_get.. but the new introduced
> kexec_* function does not work on some laptops, so it is not a 100% good
> fix, I hoped we can get it working for all known issues. But if we can
> not do it eg. within one week we can go with this version and leave the
> laptop issue as a known issue.
>

Latest debugging status:

Kexec boot works with commenting out some code like below, so the guid
cmp (memcmp) caused a system reset), still need to find out why:

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index d9f9abd63c68..13e7a23ae94c 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -95,10 +95,12 @@ __efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
table = tbl->table;
}

+/*
if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
rsdp_addr = table;
else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
return table;
+*/
}

return rsdp_addr;
@@ -291,9 +293,10 @@ acpi_physical_address get_rsdp_addr(void)
if (!pa)
pa = kexec_get_rsdp_addr();

+/*
if (!pa)
pa = efi_get_rsdp_addr();
-
+*/
if (!pa)
pa = bios_get_rsdp_addr();

Thanks
Dave

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