Re: [PATCH v5 6/7] acpi/ghes: add support for generic error injection via QAPI

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Tue, 6 Aug 2024 16:31:13 +0200
Igor Mammedov <imammedo@redhat.com> wrote:

> On Fri,  2 Aug 2024 23:44:01 +0200
> Mauro Carvalho Chehab <mchehab+huawei@kernel.org> wrote:
> 
> > Provide a generic interface for error injection via GHESv2.
> > 
> > This patch is co-authored:
> >     - original ghes logic to inject a simple ARM record by Shiju Jose;
> >     - generic logic to handle block addresses by Jonathan Cameron;
> >     - generic GHESv2 error inject by Mauro Carvalho Chehab;
> > 
> > Co-authored-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Co-authored-by: Shiju Jose <shiju.jose@huawei.com>
> > Co-authored-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> > Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Cc: Shiju Jose <shiju.jose@huawei.com>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> > ---
> >  hw/acpi/ghes.c         | 159 ++++++++++++++++++++++++++++++++++++++---
> >  hw/acpi/ghes_cper.c    |   2 +-
> >  include/hw/acpi/ghes.h |   3 +
> >  3 files changed, 152 insertions(+), 12 deletions(-)
> > 
> > diff --git a/hw/acpi/ghes.c b/hw/acpi/ghes.c
> > index a745dcc7be5e..e125c9475773 100644
> > --- a/hw/acpi/ghes.c
> > +++ b/hw/acpi/ghes.c
> > @@ -395,23 +395,22 @@ void acpi_ghes_add_fw_cfg(AcpiGhesState *ags, FWCfgState *s,
> >      ags->present = true;
> >  }
> >  
> > +static uint64_t ghes_get_state_start_address(void)  
> 
> ghes_get_hardware_errors_address() might better reflect what address it will return
> 
> > +{
> > +    AcpiGedState *acpi_ged_state =
> > +        ACPI_GED(object_resolve_path_type("", TYPE_ACPI_GED, NULL));
> > +    AcpiGhesState *ags = &acpi_ged_state->ghes_state;
> > +
> > +    return le64_to_cpu(ags->ghes_addr_le);
> > +}
> > +
> >  int acpi_ghes_record_errors(uint8_t source_id, uint64_t physical_address)
> >  {
> >      uint64_t error_block_addr, read_ack_register_addr, read_ack_register = 0;
> > -    uint64_t start_addr;
> > +    uint64_t start_addr = ghes_get_state_start_address();
> >      bool ret = -1;
> > -    AcpiGedState *acpi_ged_state;
> > -    AcpiGhesState *ags;
> > -
> >      assert(source_id < ACPI_HEST_SRC_ID_RESERVED);
> >  
> > -    acpi_ged_state = ACPI_GED(object_resolve_path_type("", TYPE_ACPI_GED,
> > -                                                       NULL));
> > -    g_assert(acpi_ged_state);
> > -    ags = &acpi_ged_state->ghes_state;
> > -
> > -    start_addr = le64_to_cpu(ags->ghes_addr_le);
> > -
> >      if (physical_address) {
> >          start_addr += source_id * sizeof(uint64_t);  
> 
> above should be a separate patch
> 
> >  
> > @@ -448,9 +447,147 @@ int acpi_ghes_record_errors(uint8_t source_id, uint64_t physical_address)
> >      return ret;
> >  }
> >  
> > +/*
> > + * Error register block data layout
> > + *
> > + * | +---------------------+ ges.ghes_addr_le
> > + * | |error_block_address0 |
> > + * | +---------------------+
> > + * | |error_block_address1 |
> > + * | +---------------------+ --+--
> > + * | |    .............    | GHES_ADDRESS_SIZE
> > + * | +---------------------+ --+--
> > + * | |error_block_addressN |
> > + * | +---------------------+
> > + * | | read_ack0           |
> > + * | +---------------------+ --+--
> > + * | | read_ack1           | GHES_ADDRESS_SIZE
> > + * | +---------------------+ --+--
> > + * | |   .............     |
> > + * | +---------------------+
> > + * | | read_ackN           |
> > + * | +---------------------+ --+--
> > + * | |      CPER           |   |
> > + * | |      ....           | GHES_MAX_RAW_DATA_LENGT
> > + * | |      CPER           |   |
> > + * | +---------------------+ --+--
> > + * | |    ..........       |
> > + * | +---------------------+
> > + * | |      CPER           |
> > + * | |      ....           |
> > + * | |      CPER           |
> > + * | +---------------------+
> > + */  
> 
> no need to duplicate docs/specs/acpi_hest_ghes.rst,
> I'd just reffer to it and maybe add short comment as to why it's mentioned.
> 
> > +/* Map from uint32_t notify to entry offset in GHES */
> > +static const uint8_t error_source_to_index[] = { 0xff, 0xff, 0xff, 0xff,
> > +                                                 0xff, 0xff, 0xff, 1, 0};
> > +
> > +static bool ghes_get_addr(uint32_t notify, uint64_t *error_block_addr,
> > +                          uint64_t *read_ack_addr)
> > +{
> > +    uint64_t base;
> > +
> > +    if (notify >= ACPI_GHES_NOTIFY_RESERVED) {
> > +        return false;
> > +    }
> > +
> > +    /* Find and check the source id for this new CPER */
> > +    if (error_source_to_index[notify] == 0xff) {
> > +        return false;
> > +    }
> > +
> > +    base = ghes_get_state_start_address();
> > +
> > +    *read_ack_addr = base +
> > +        ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t) +
> > +        error_source_to_index[notify] * sizeof(uint64_t);
> > +
> > +    /* Could also be read back from the error_block_address register */
> > +    *error_block_addr = base +
> > +        ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t) +
> > +        ACPI_GHES_ERROR_SOURCE_COUNT * sizeof(uint64_t) +
> > +        error_source_to_index[notify] * ACPI_GHES_MAX_RAW_DATA_LENGTH;
> > +
> > +    return true;
> > +}  
> 
> I don't like all this pointer math, which is basically a reverse engineered
> QEMU actions on startup + guest provided etc/hardware_errors address.
> 
> For once, it assumes error_source_to_index[] matches order in which HEST
> error sources were described, which is fragile.
> 
> 2nd: migration-wive it's disaster, since old/new HEST/hardware_errors tables
> in RAM migrated from older version might not match above assumptions
> of target QEMU. 
> 
> I see 2 ways to rectify it:
>   1st: preferred/cleanest would be to tell QEMU (via fw_cfg) address of HEST table
>        in guest RAM, like we do with etc/hardware_errors, see
>             build_ghes_error_table()
>                ...
>                tell firmware to write hardware_errors GPA into
>        and then fetch from HEST table in RAM, the guest patched error/ack addresses
>        for given source_id
> 
>        code-wise: relatively simple once one wraps their own head over
>                  how this whole APEI thing works in QEMU
>                  workflow  is described in docs/specs/acpi_hest_ghes.rst
>                  look to me as sufficient to grasp it.
>                  (but my view is very biased given my prior knowledge,
>                   aka: docs/comments/examples wrt acpi patching are good enough)
>                  (if it's not clear how to do it, ask me for pointers)

Hi Igor, I think I follow what you mean but maybe this question will reveal
otherwise.  HEST is currently in ACPI_BUILD_TABLE_FILE.
Would you suggest splitting it to it's own file, or using table_offsets
to get the offset in ACPI_BUILD_TABLE_FILE GPA?