linux-kernel - RE: [PATCH v3 2/8] efi: Decode IA32/X64 Processor Error Section

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Date:   Thu, 29 Mar 2018 13:47:03 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>
Subject: RE: [PATCH v3 2/8] efi: Decode IA32/X64 Processor Error Section

> -----Original Message-----
> From: Borislav Petkov <bp@...en8.de>
> Sent: Thursday, March 29, 2018 5:46 AM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>
> Cc: linux-efi@...r.kernel.org; linux-kernel@...r.kernel.org;
> ard.biesheuvel@...aro.org; x86@...nel.org; tony.luck@...el.com
> Subject: Re: [PATCH v3 2/8] efi: Decode IA32/X64 Processor Error Section
> 
> On Sat, Mar 24, 2018 at 01:49:34PM -0500, Yazen Ghannam wrote:
> > From: Yazen Ghannam <yazen.ghannam@....com>
> >
> > Recognize the IA32/X64 Processor Error Section.
> >
> > Do the section decoding in a new "cper-x86.c" file and add this to the
> > Makefile depending on a new "UEFI_CPER_X86" config option.
> >
> > Print the Local APIC ID and CPUID info from the Processor Error Record.
> >
> > The "Processor Error Info" and "Processor Context" fields will be
> > decoded in following patches.
> >
> > Based on UEFI 2.7 Table 252. Processor Error Record.
> >
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> > ---
> > Link:
> > https://lkml.kernel.org/r/20180226193904.20532-3-
> Yazen.Ghannam@....com
> >
> > v2->v3:
> > * Fix table number in commit message.
> > * Don't print raw validation bits.
> >
> > v1->v2:
> > * Change config option depends to "X86" instead of "X86_32 || X64_64".
> > * Remove extra newline in Makefile changes.
> > * Drop author copyright line.
> >
> >  drivers/firmware/efi/Kconfig    |  5 +++++
> >  drivers/firmware/efi/Makefile   |  1 +
> >  drivers/firmware/efi/cper-x86.c | 23 +++++++++++++++++++++++
> 
> I'd prefer if that were:
> 
> drivers/firmware/efi/cper/x86.c
> drivers/firmware/efi/cper/arm.c
> 
> but that's Ard's call.
> 
> >  drivers/firmware/efi/cper.c     | 10 ++++++++++
> >  include/linux/cper.h            |  2 ++
> >  5 files changed, 41 insertions(+)
> >  create mode 100644 drivers/firmware/efi/cper-x86.c
> >
> > diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
> > index 3098410abad8..781a4a337557 100644
> > --- a/drivers/firmware/efi/Kconfig
> > +++ b/drivers/firmware/efi/Kconfig
> > @@ -174,6 +174,11 @@ config UEFI_CPER_ARM
> >  	depends on UEFI_CPER && ( ARM || ARM64 )
> >  	default y
> >
> > +config UEFI_CPER_X86
> > +	bool
> > +	depends on UEFI_CPER && X86
> > +	default y
> > +
> >  config EFI_DEV_PATH_PARSER
> >  	bool
> >  	depends on ACPI
> > diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
> > index cb805374f4bc..5f9f5039de50 100644
> > --- a/drivers/firmware/efi/Makefile
> > +++ b/drivers/firmware/efi/Makefile
> > @@ -31,3 +31,4 @@ obj-$(CONFIG_ARM)			+= $(arm-obj-
> y)
> >  obj-$(CONFIG_ARM64)			+= $(arm-obj-y)
> >  obj-$(CONFIG_EFI_CAPSULE_LOADER)	+= capsule-loader.o
> >  obj-$(CONFIG_UEFI_CPER_ARM)		+= cper-arm.o
> > +obj-$(CONFIG_UEFI_CPER_X86)		+= cper-x86.o
> > diff --git a/drivers/firmware/efi/cper-x86.c b/drivers/firmware/efi/cper-
> x86.c
> > new file mode 100644
> > index 000000000000..863f0cd2a0ff
> > --- /dev/null
> > +++ b/drivers/firmware/efi/cper-x86.c
> > @@ -0,0 +1,23 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (C) 2018, Advanced Micro Devices, Inc.
> > +
> > +#include <linux/cper.h>
> > +
> > +/*
> > + * We don't need a "CPER_IA" prefix since these are all locally defined.
> > + * This will save us a lot of line space.
> > + */
> > +#define VALID_LAPIC_ID			BIT_ULL(0)
> > +#define VALID_CPUID_INFO		BIT_ULL(1)
> > +
> > +void cper_print_proc_ia(const char *pfx, const struct cper_sec_proc_ia
> *proc)
> > +{
> > +	if (proc->validation_bits & VALID_LAPIC_ID)
> > +		printk("%sLocal APIC_ID: 0x%llx\n", pfx, proc->lapic_id);
> > +
> > +	if (proc->validation_bits & VALID_CPUID_INFO) {
> > +		printk("%sCPUID Info:\n", pfx);
> > +		print_hex_dump(pfx, "", DUMP_PREFIX_OFFSET, 16, 4, proc-
> >cpuid,
> > +			       sizeof(proc->cpuid), 0);
> 
> That's dumping 48 bytes of static information for every error!
> Information which can be dumped only once when collecting system info.
> 

Right, but here we just print the record as-is. We can do it different when
this hooks into the MCA decoding. And the use-case at the moment is for
BERT which shouldn't have very many errors.

Thanks,
Yazen