linux-kernel - Re: [PATCH v6 18/19] docs: hest: add new "etc/acpi_table_hest

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Message-ID: <20250228140819.322e6390@imammedo.users.ipa.redhat.com>
Date: Fri, 28 Feb 2025 14:08:19 +0100
From: Igor Mammedov <imammedo@...hat.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>, "Michael S . Tsirkin"
 <mst@...hat.com>, Shiju Jose <shiju.jose@...wei.com>,
 <qemu-arm@...gnu.org>, <qemu-devel@...gnu.org>, Dongjiu Geng
 <gengdongjiu1@...il.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 18/19] docs: hest: add new "etc/acpi_table_hest_addr"
 and update workflow

On Fri, 28 Feb 2025 17:36:08 +0800
Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:

> On Thu, 27 Feb 2025 17:00:56 +0100
> Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:
> 
> > While the HEST layout didn't change, there are some internal
> > changes related to how offsets are calculated and how memory error
> > events are triggered.
> > 
> > Update specs to reflect such changes.
> > 
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>  
> One minor editorial suggestion. With that or similar tidy up,
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

with nit below fixed,

Reviewed-by: Igor Mammedov <imammedo@...hat.com>

> 
> > ---
> >  docs/specs/acpi_hest_ghes.rst | 28 +++++++++++++++++-----------
> >  1 file changed, 17 insertions(+), 11 deletions(-)
> > 
> > diff --git a/docs/specs/acpi_hest_ghes.rst b/docs/specs/acpi_hest_ghes.rst
> > index c3e9f8d9a702..4311a9536b21 100644
> > --- a/docs/specs/acpi_hest_ghes.rst
> > +++ b/docs/specs/acpi_hest_ghes.rst
> > @@ -89,12 +89,21 @@ Design Details
> >      addresses in the "error_block_address" fields with a pointer to the
> >      respective "Error Status Data Block" in the "etc/hardware_errors" blob.
> >  
> > -(8) QEMU defines a third and write-only fw_cfg blob which is called
> > -    "etc/hardware_errors_addr". Through that blob, the firmware can send back
> > -    the guest-side allocation addresses to QEMU. The "etc/hardware_errors_addr"
> > -    blob contains a 8-byte entry. QEMU generates a single WRITE_POINTER command
> > -    for the firmware. The firmware will write back the start address of
> > -    "etc/hardware_errors" blob to the fw_cfg file "etc/hardware_errors_addr".
> > +(8) QEMU defines a third and write-only fw_cfg blob to store the location
> > +    where the error block offsets, read ack registers and CPER records are
> > +    stored.
> > +
> > +    Up to QEMU 9.2, the location was at "etc/hardware_errors_addr", and
> > +    contains a GPA for the beginning of "etc/hardware_errors".
> > +
> > +    Newer versions place the location at "etc/acpi_table_hest_addr",
> > +    pointing to the GPA of the HEST table.
> > +
> > +    Through that such GPA values, the firmware can send back the guest-side  
> This confuses me.
>  Via those GPA values...? (maybe?)

it's not GPA here, it should be fwcfg.
Maybe something like this
 "Using above mentioned 'fwcfg' files,"

> 
> > +    allocation addresses to QEMU. They contain a 8-byte entry. QEMU generates
> > +    a single WRITE_POINTER command for the firmware. The firmware will write
> > +    back the start address of either "etc/hardware_errors" or HEST table at
> > +    the corresponding fw_cfg file.
> >  
> >  (9) When QEMU gets a SIGBUS from the kernel, QEMU writes CPER into corresponding
> >      "Error Status Data Block", guest memory, and then injects platform specific
> > @@ -105,8 +114,5 @@ Design Details
> >       kernel, on receiving notification, guest APEI driver could read the CPER error
> >       and take appropriate action.
> >  
> > -(11) kvm_arch_on_sigbus_vcpu() uses source_id as index in "etc/hardware_errors" to
> > -     find out "Error Status Data Block" entry corresponding to error source. So supported
> > -     source_id values should be assigned here and not be changed afterwards to make sure
> > -     that guest will write error into expected "Error Status Data Block" even if guest was
> > -     migrated to a newer QEMU.
> > +(11) kvm_arch_on_sigbus_vcpu() report RAS errors via a SEA notifications,
> > +     when a SIGBUS event is triggered.  
>