linux-kernel - Re: [PATCH v8 06/13] acpi/ghes: add support for generic error injection via QAPI

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Message-ID: <20240825052923.715f88bc@sal.lan>
Date: Sun, 25 Aug 2024 05:29:23 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Igor Mammedov <imammedo@...hat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, Shiju Jose
 <shiju.jose@...wei.com>, "Michael S. Tsirkin" <mst@...hat.com>, Ani Sinha
 <anisinha@...hat.com>, Dongjiu Geng <gengdongjiu1@...il.com>,
 linux-kernel@...r.kernel.org, qemu-arm@...gnu.org, qemu-devel@...gnu.org
Subject: Re: [PATCH v8 06/13] acpi/ghes: add support for generic error
 injection via QAPI

Em Mon, 19 Aug 2024 14:51:36 +0200
Igor Mammedov <imammedo@...hat.com> escreveu:

> > +        read_ack = 1;
> > +        cpu_physical_memory_write(read_ack_start_addr,
> > +                                  &read_ack, (uint64_t));  
> we don't do this for SEV so, why are you setting it to 1 here?

According with:
https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#generic-hardware-error-source-version-2-ghesv2-type-10

   "These are the steps the OS must take once detecting an error from a particular GHESv2 error source:

    OSPM detects error (via interrupt/exception or polling the block status)

    OSPM copies the error status block

    OSPM clears the block status field of the error status block

    OSPM acknowledges the error via Read Ack register. For example:

        OSPM reads the Read Ack register –> X

        OSPM writes –> (( X & ReadAckPreserve) | ReadAckWrite)"

So, basically the guest OS takes some time to detect that an error
is raised. When it detects, it needs to mark that the error was
handled.

IMO, this is needed, independently of the notification mechanism.

Regards,
Mauro