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

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Em Tue, 3 Dec 2024 12:51:43 +0100
Igor Mammedov <imammedo@redhat.com> escreveu:

> On Fri, 22 Nov 2024 10:11:30 +0100
> Mauro Carvalho Chehab <mchehab+huawei@kernel.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@kernel.org>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.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?

It is a safeguard measure to avoid crashes and OOM access. If fw_cfg 
callback doesn't fill it properly, this will be zero.

> > +
> > +    /*
> > +     * 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.

It may fail due to:

    if (!ghes_addr) {
        return;
    }

> 
> >      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()

Ok, I'll drop this one.

> > +    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;
> >  }  
> 

Thanks,
Mauro