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

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 7 Aug 2024 15:25:47 +0100
Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:

> 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?
yep, offset taken right before HEST is to be created
doc comment for bios_linker_loader_write_pointer() explains how it works

we need something like:
       bios_linker_loader_write_pointer(linker,
           ACPI_HEST_TABLE_ADDR_FW_CFG_FILE, 0, sizeof(uint64_t),
           ACPI_BUILD_TABLE_FILE, hest_offset_within_ACPI_BUILD_TABLE_FILE); 

to register new file see:
   a08a64627 ACPI: Record the Generic Error Status Block address
   and to avoid copy past error maybe
   136fc6aa2 ACPI: Avoid infinite recursion when dump-vmstat
for this needs to be limited to new machine types and keep
old ones without this new feature. (I'd use hw_compat_ machinery for that)

while at it we should rename
  ACPI_GHES_DATA_ADDR_FW_CFG_FILE -> ACPI_GHES_ERRORS_ADDR_FW_CFG_FILE