linux-kernel - Re: [PATCH v4 13/15] acpi/ghes: move offset calculus to a separate function

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Message-ID: <20241203125143.7171892a@imammedo.users.ipa.redhat.com>
Date: Tue, 3 Dec 2024 12:51:43 +0100
From: Igor Mammedov <imammedo@...hat.com>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
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 v4 13/15] acpi/ghes: move offset calculus to a separate
 function

On Fri, 22 Nov 2024 10:11:30 +0100
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:

> Currently, CPER address location is calculated as an offset of
> the hardware_errors table. It is also badly named, as the
> offset actually used is the address where the CPER data starts,
> and not the beginning of the error source.
> 
> Move the logic which calculates such offset to a separate
> function, in preparation for a patch that will be changing the
> logic to calculate it from the HEST table.
> 
> While here, properly name the variable which stores the cper
> address.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  hw/acpi/ghes.c | 41 ++++++++++++++++++++++++++++++++---------
>  1 file changed, 32 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/acpi/ghes.c b/hw/acpi/ghes.c
> index 87fd3feedd2a..d99697b20164 100644
> --- a/hw/acpi/ghes.c
> +++ b/hw/acpi/ghes.c
> @@ -364,10 +364,37 @@ void acpi_ghes_add_fw_cfg(AcpiGhesState *ags, FWCfgState *s,
>      ags->present = true;
>  }
>  
> +static void get_hw_error_offsets(uint64_t ghes_addr,
> +                                 uint64_t *cper_addr,
> +                                 uint64_t *read_ack_register_addr)
> +{


> +    if (!ghes_addr) {
> +        return;
> +    }

why do we need this check?

> +
> +    /*
> +     * non-HEST version supports only one source, so no need to change
> +     * the start offset based on the source ID. Also, we can't validate
> +     * the source ID, as it is stored inside the HEST table.
> +     */
> +
> +    cpu_physical_memory_read(ghes_addr, cper_addr,
> +                             sizeof(*cper_addr));
> +
> +    *cper_addr = le64_to_cpu(*cper_addr);
        1st bits flip, and then see later

> +
> +    /*
> +     * As the current version supports only one source, the ack offset is
> +     * just sizeof(uint64_t).
> +     */
> +    *read_ack_register_addr = ghes_addr +
> +			      ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t);
> +}
> +
>  void ghes_record_cper_errors(const void *cper, size_t len,
>                               uint16_t source_id, Error **errp)
>  {
> -    uint64_t error_block_addr, read_ack_register_addr, read_ack_register = 0;
> +    uint64_t cper_addr = 0, read_ack_register_addr = 0, read_ack_register;

if get_hw_error_offsets() isn't supposed to fail, then we do not need to initialize
above. So this hunk doesn't belong to this patch.

>      uint64_t start_addr;
>      AcpiGedState *acpi_ged_state;
>      AcpiGhesState *ags;
> @@ -389,18 +416,14 @@ void ghes_record_cper_errors(const void *cper, size_t len,
>  
>      start_addr += source_id * sizeof(uint64_t);
>  
> -    cpu_physical_memory_read(start_addr, &error_block_addr,
> -                             sizeof(error_block_addr));
> +    get_hw_error_offsets(start_addr, &cper_addr, &read_ack_register_addr);
>  
> -    error_block_addr = le64_to_cpu(error_block_addr);
> -    if (!error_block_addr) {
> +    cper_addr = le64_to_cpu(cper_addr);
                   ^^^^ 2nd bits flip turning it back to guest byte order again

suggest to keep only one of them in get_hw_error_offsets()

> +    if (!cper_addr) {
>          error_setg(errp, "can not find Generic Error Status Block");
>          return;
>      }
>  
> -    read_ack_register_addr = start_addr +
> -                             ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t);
> -
>      cpu_physical_memory_read(read_ack_register_addr,
>                               &read_ack_register, sizeof(read_ack_register));
>  
> @@ -421,7 +444,7 @@ void ghes_record_cper_errors(const void *cper, size_t len,
>          &read_ack_register, sizeof(uint64_t));
>  
>      /* Write the generic error data entry into guest memory */
> -    cpu_physical_memory_write(error_block_addr, cper, len);
> +    cpu_physical_memory_write(cper_addr, cper, len);
>  
>      return;
>  }