Re: [PATCH v2 1/4] ACPICA: Fix PCC OperationRegion command offsets

On Wed, Aug 05, 2026 at 06:46:15PM +0200, Rafael J. Wysocki (Intel) wrote:
> On Wed, Jul 22, 2026 at 3:16 PM Sudeep Holla <[email protected]> wrote:
> >
> > ACPI 6.3, section 5.5.2.4.7.3, states that the PCC Operation
> > Region is associated with the region of shared memory that follows the
> > PCC signature.
> >
> > The generic and extended PCC shared memory layouts include the 4-byte
> > signature at offset 0, so their raw shared memory COMMAND fields are at
> > offsets 4 and 12 respectively. Since AML field offsets for the PCC
> > OperationRegion are relative to the region after that signature, ACPICA
> > must look for those COMMAND fields at OperationRegion offsets 0 and 8.
> >
> > Adjust the generic and master subspace command checks to use those
> > OperationRegion-relative offsets. Otherwise writes to the COMMAND field
> > can fail to invoke the PCC address space handler at the offset described
> > by the PCC OperationRegion definition.
> >
> > Fixes: aa6ec56b574d ("ACPICA: ACPI 6.3: add PCC operation region support for AML interpreter")
> > Signed-off-by: Sudeep Holla <[email protected]>
> > ---
> >  drivers/acpi/acpica/exfield.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/acpi/acpica/exfield.c b/drivers/acpi/acpica/exfield.c
> > index 9a55524ed8f4..a7fac63938b3 100644
> > --- a/drivers/acpi/acpica/exfield.c
> > +++ b/drivers/acpi/acpica/exfield.c
> > @@ -45,12 +45,13 @@ static const u8 acpi_protocol_lengths[] = {
> >
> >  /*
> >   * The following macros determine a given offset is a COMD field.
> > - * According to the specification, generic subspaces (types 0-2) contains a
> > - * 2-byte COMD field at offset 4 and master subspaces (type 3) contains a 4-byte
> > - * COMD field starting at offset 12.
> > + * According to the specification, the PCC OperationRegion begins after
> > + * the PCC signature. The raw shared memory COMD offsets of 4 for generic
> > + * subspaces (types 0-2) and 12 for master subspaces (type 3) therefore
> > + * appear at OperationRegion offsets 0 and 8.
> >   */
> > -#define GENERIC_SUBSPACE_COMMAND(a)     (4 == a || a == 5)
> > -#define MASTER_SUBSPACE_COMMAND(a)      (12 <= a && a <= 15)
> > +#define GENERIC_SUBSPACE_COMMAND(a)     ((a) < 2)
> > +#define MASTER_SUBSPACE_COMMAND(a)      (((a) - 8) < 4)
> >
> >  /*******************************************************************************
> >   *
> > --
> 
> Can you please see the corresponding upstream ACPICA pull request?
> There are concerns regarding it.
> 

Sorry for the delay in response, currently I am on vacation and don't
have all the setup to validate anything. I will follow up once I am back.
It is OK to miss v7.3

-- 
Regards,
Sudeep