linux-kernel - Re: [PATCH] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernels

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Date:   Wed, 17 Apr 2019 12:57:42 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Junichi Nomura <j-nomura@...jp.nec.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        Baoquan He <bhe@...hat.com>, Kairui Song <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [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