Re: [PATCH v5 03/18] hw/arm/smmuv3: Fix encoding of CLASS in events

[Jean-Philippe Brucker]

Hi Eric,

On Wed, Jul 17, 2024 at 05:07:57PM +0200, Eric Auger wrote:
> Hi Jean,
> 
> On 7/15/24 10:45, Mostafa Saleh wrote:
> > The SMMUv3 spec (ARM IHI 0070 F.b - 7.3 Event records) defines the
> > class of events faults as:
> >
> > CLASS: The class of the operation that caused the fault:
> > - 0b00: CD, CD fetch.
> > - 0b01: TTD, Stage 1 translation table fetch.
> > - 0b10: IN, Input address
> >
> > However, this value was not set and left as 0 which means CD and not
> > IN (0b10).
> >
> > Another problem was that stage-2 class is considered IN not TT for
> > EABT, according to the spec:
> >     Translation of an IPA after successful stage 1 translation (or,
> >     in stage 2-only configuration, an input IPA)
> >     - S2 == 1 (stage 2), CLASS == IN (Input to stage)
> >
> > This would change soon when nested translations are supported.
> >
> > While at it, add an enum for class as it would be used for nesting.
> > However, at the moment stage-1 and stage-2 use the same class values,
> > except for EABT.
> >
> > Fixes: 9bde7f0674 “hw/arm/smmuv3: Implement translate callback”
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  hw/arm/smmuv3-internal.h | 6 ++++++
> >  hw/arm/smmuv3.c          | 8 +++++++-
> >  2 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/arm/smmuv3-internal.h b/hw/arm/smmuv3-internal.h
> > index e4dd11e1e6..0f3ecec804 100644
> > --- a/hw/arm/smmuv3-internal.h
> > +++ b/hw/arm/smmuv3-internal.h
> > @@ -32,6 +32,12 @@ typedef enum SMMUTranslationStatus {
> >      SMMU_TRANS_SUCCESS,
> >  } SMMUTranslationStatus;
> >  
> > +typedef enum SMMUTranslationClass {
> > +    SMMU_CLASS_CD,
> > +    SMMU_CLASS_TT,
> > +    SMMU_CLASS_IN,
> > +} SMMUTranslationClass;
> > +
> >  /* MMIO Registers */
> >  
> >  REG32(IDR0,                0x0)
> > diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> > index 9dd3ea48e4..3d214c9f57 100644
> > --- a/hw/arm/smmuv3.c
> > +++ b/hw/arm/smmuv3.c
> > @@ -942,7 +942,9 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion 
> > *mr, hwaddr addr,
> >              event.type = SMMU_EVT_F_WALK_EABT;
> >              event.u.f_walk_eabt.addr = addr;
> >              event.u.f_walk_eabt.rnw = flag & 0x1;
> > -            event.u.f_walk_eabt.class = 0x1;
> > +            /* Stage-2 (only) is class IN while stage-1 is class TT */
> > +            event.u.f_walk_eabt.class = (ptw_info.stage == 2) ?
> > +                                         SMMU_CLASS_IN : SMMU_CLASS_TT;
> does it match your expectations. While reading your previous comment I
> have the impression what you had in mind was more complicated than that
> 
> * s2 walk that encounters EABT on S2 descriptor while translating
>   non-descriptor IPA is reported as class=IN, even when doing s2-only.

At this point we only support single-stage, so I believe this is correct:
        "A stage 1-only table walk that encounters EABT ... CLASS == TT"
        "translation of ... in stage 2-only configuration, an input IPA...
         CLASS == IN"

Later in the series this code changes in order to support nesting, but I
think it's still correct, because the EABT class works similarly to
translation errors, except for stage-1 faults which have CLASS==TT

Thanks,
Jean

> 
> Thanks
> 
> Eric
> 
> >              event.u.f_walk_eabt.addr2 = ptw_info.addr;
> >              break;
> >          case SMMU_PTW_ERR_TRANSLATION:
> > @@ -950,6 +952,7 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion 
> > *mr, hwaddr addr,
> >                  event.type = SMMU_EVT_F_TRANSLATION;
> >                  event.u.f_translation.addr = addr;
> >                  event.u.f_translation.addr2 = ptw_info.addr;
> > +                event.u.f_translation.class = SMMU_CLASS_IN;
> >                  event.u.f_translation.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -958,6 +961,7 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion 
> > *mr, hwaddr addr,
> >                  event.type = SMMU_EVT_F_ADDR_SIZE;
> >                  event.u.f_addr_size.addr = addr;
> >                  event.u.f_addr_size.addr2 = ptw_info.addr;
> > +                event.u.f_translation.class = SMMU_CLASS_IN;
> >                  event.u.f_addr_size.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -966,6 +970,7 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion 
> > *mr, hwaddr addr,
> >                  event.type = SMMU_EVT_F_ACCESS;
> >                  event.u.f_access.addr = addr;
> >                  event.u.f_access.addr2 = ptw_info.addr;
> > +                event.u.f_translation.class = SMMU_CLASS_IN;
> >                  event.u.f_access.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -974,6 +979,7 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion 
> > *mr, hwaddr addr,
> >                  event.type = SMMU_EVT_F_PERMISSION;
> >                  event.u.f_permission.addr = addr;
> >                  event.u.f_permission.addr2 = ptw_info.addr;
> > +                event.u.f_translation.class = SMMU_CLASS_IN;
> >                  event.u.f_permission.rnw = flag & 0x1;
> >              }
> >              break;
>