Re: [RFC PATCH v3 07/18] hw/arm/smmuv3: Translate CD and TT using stage-2 table

[Mostafa Saleh <smostafa@google.com>]

Hi Eric,

On Wed, May 15, 2024 at 03:15:02PM +0200, Eric Auger wrote:
> Hi Mostafa,
> 
> On 4/29/24 05:23, Mostafa Saleh wrote:
> > According to ARM SMMU architecture specification (ARM IHI 0070 F.b),
> > In "5.2 Stream Table Entry":
> >  [51:6] S1ContextPtr
> >  If Config[1] == 1 (stage 2 enabled), this pointer is an IPA translated by
> >  stage 2 and the programmed value must be within the range of the IAS.
> >
> > In "5.4.1 CD notes":
> >  The translation table walks performed from TTB0 or TTB1 are always performed
> >  in IPA space if stage 2 translations are enabled.
> >
> > This patch implements translation of the S1 context descriptor pointer and
> > TTBx base addresses through the S2 stage (IPA -> PA)
> >
> > smmuv3_do_translate() is updated to have one arg which is translation
> > class, this is useful for:
> s/for/to?
Will do.
> >  - Decide wether a translation is stage-2 only or use the STE config.
> >  - Populate the class in case of faults, WALK_EABT is lefat as it as
> left unchanged?
Yup, that's a typo.
> >    it is always triggered from TT access so no need to use the input
> >    class.
> >
> > In case for stage-2 only translation, which only used in nesting, the
> in case of S2 translation used in the contexted of a nested translation, ...
Will do.
> > stage and asid are saved and restored before and after calling
> > smmu_translate().
> >
> > Translating CD or TTBx can fail for the following reasons:
> > 1) Large address size: This is described in
> >    (3.4.3 Address sizes of SMMU-originated accesses)
> >    - For CD ptr larger than IAS, for SMMUv3.1, it can trigger either
> >      C_BAD_STE or Translation fault, we implement the latter as it
> >      requires no extra code.
> >    - For TTBx, if larger than the effective stage 1 output address size, it
> >      triggers C_BAD_CD.
> >
> > 2) Faults from PTWs (7.3 Event records)
> >    - F_ADDR_SIZE: large address size after first level causes stage 2 Address
> >      Size fault (Also in 3.4.3 Address sizes of SMMU-originated accesses)
> >    - F_PERMISSION: Same as an address translation. However, when
> >      CLASS == CD, the access is implicitly Data and a read.
> >    - F_ACCESS: Same as an address translation.
> >    - F_TRANSLATION: Same as an address translation.
> >    - F_WALK_EABT: Same as an address translation.
> >   These are already implemented in the PTW logic, so no extra handling
> >   required.
> >
> > As, there is multiple locations where the address is calculated from
> > cached entry, a new macro is introduced CACHED_ENTRY_TO_ADDR.
> >
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  hw/arm/smmuv3.c              | 76 ++++++++++++++++++++++++++++++------
> >  include/hw/arm/smmu-common.h |  3 ++
> >  2 files changed, 66 insertions(+), 13 deletions(-)
> >
> > diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> > index cc61708160..cc61c82321 100644
> > --- a/hw/arm/smmuv3.c
> > +++ b/hw/arm/smmuv3.c
> > @@ -337,14 +337,33 @@ static int smmu_get_ste(SMMUv3State *s, dma_addr_t addr, STE *buf,
> >  
> >  }
> >  
> > +static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, hwaddr addr,
> > +                                                 SMMUTransCfg *cfg,
> > +                                                 SMMUEventInfo *event,
> > +                                                 IOMMUAccessFlags flag,
> > +                                                 SMMUTLBEntry **out_entry,
> > +                                                 SMMUTranslationClass class);
> >  /* @ssid > 0 not supported yet */
> > -static int smmu_get_cd(SMMUv3State *s, STE *ste, uint32_t ssid,
> > -                       CD *buf, SMMUEventInfo *event)
> > +static int smmu_get_cd(SMMUv3State *s, STE *ste, SMMUTransCfg *cfg,
> > +                       uint32_t ssid, CD *buf, SMMUEventInfo *event)
> >  {
> >      dma_addr_t addr = STE_CTXPTR(ste);
> >      int ret, i;
> > +    SMMUTranslationStatus status;
> > +    SMMUTLBEntry *entry;
> >  
> >      trace_smmuv3_get_cd(addr);
> > +
> > +    if (cfg->stage == SMMU_NESTED) {
> > +        status = smmuv3_do_translate(s, addr, cfg, event,
> > +                                     IOMMU_RO, &entry, SMMU_CLASS_CD);
> > +        if (status != SMMU_TRANS_SUCCESS) {
> So I guess you rely on event being populated by above CD S2 translate().
> it does not need to be patched, correct?
> May be worth a comment.
Yes, only the class is different, I will add a comment.
> > +            return -EINVAL;
> > +        }
> > +
> > +        addr = CACHED_ENTRY_TO_ADDR(entry, addr);
> > +    }
> > +
> >      /* TODO: guarantee 64-bit single-copy atomicity */
> >      ret = dma_memory_read(&address_space_memory, addr, buf, sizeof(*buf),
> >                            MEMTXATTRS_UNSPECIFIED);
> > @@ -659,10 +678,13 @@ static int smmu_find_ste(SMMUv3State *s, uint32_t sid, STE *ste,
> >      return 0;
> >  }
> >  
> > -static int decode_cd(SMMUTransCfg *cfg, CD *cd, SMMUEventInfo *event)
> > +static int decode_cd(SMMUv3State *s, SMMUTransCfg *cfg,
> > +                     CD *cd, SMMUEventInfo *event)
> >  {
> >      int ret = -EINVAL;
> >      int i;
> > +    SMMUTranslationStatus status;
> > +    SMMUTLBEntry *entry;
> >  
> >      if (!CD_VALID(cd) || !CD_AARCH64(cd)) {
> >          goto bad_cd;
> > @@ -713,9 +735,21 @@ static int decode_cd(SMMUTransCfg *cfg, CD *cd, SMMUEventInfo *event)
> >  
> >          tt->tsz = tsz;
> >          tt->ttb = CD_TTB(cd, i);
> > +
> >          if (tt->ttb & ~(MAKE_64BIT_MASK(0, cfg->oas))) {
> >              goto bad_cd;
> >          }
> > +
> > +        /* Translate the TTBx, from IPA to PA if nesting is enabled. */
> > +        if (cfg->stage == SMMU_NESTED) {
> > +            status = smmuv3_do_translate(s, tt->ttb, cfg, event, IOMMU_RO,
> > +                                         &entry, SMMU_CLASS_TT);
> > +            if (status != SMMU_TRANS_SUCCESS) {
> same here.
> > +                return -EINVAL;
> > +            }
> > +            tt->ttb = CACHED_ENTRY_TO_ADDR(entry, tt->ttb);
> > +        }
> > +
> >          tt->had = CD_HAD(cd, i);
> >          trace_smmuv3_decode_cd_tt(i, tt->tsz, tt->ttb, tt->granule_sz, tt->had);
> >      }
> > @@ -767,12 +801,12 @@ static int smmuv3_decode_config(IOMMUMemoryRegion *mr, SMMUTransCfg *cfg,
> >          return 0;
> >      }
> >  
> > -    ret = smmu_get_cd(s, &ste, 0 /* ssid */, &cd, event);
> > +    ret = smmu_get_cd(s, &ste, cfg, 0 /* ssid */, &cd, event);
> >      if (ret) {
> >          return ret;
> >      }
> >  
> > -    return decode_cd(cfg, &cd, event);
> > +    return decode_cd(s, cfg, &cd, event);
> >  }
> >  
> >  /**
> > @@ -832,13 +866,29 @@ static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, hwaddr addr,
> >                                                   SMMUTransCfg *cfg,
> >                                                   SMMUEventInfo *event,
> >                                                   IOMMUAccessFlags flag,
> > -                                                 SMMUTLBEntry **out_entry)
> > +                                                 SMMUTLBEntry **out_entry,
> > +                                                 SMMUTranslationClass class)
> >  {
> >      SMMUPTWEventInfo ptw_info = {};
> >      SMMUState *bs = ARM_SMMU(s);
> >      SMMUTLBEntry *cached_entry = NULL;
> > +    int asid, stage;
> > +    bool S2_only = class != SMMU_CLASS_IN;
> > +
> > +    if (S2_only) {
> Please add a comment explaining that class value is used to identify
> S2-only forced translation in the context of a nested translation.
> In that case we hackily override the original config to reach our goal
> and then restore the original config.
> That's pretty hacky. Let's see if any other reviewer has a better idea
> ;-) on my end I understand it and I can bear the trick :)
> 
Indeed, this is unclear, I will add a comment.
I thought about this case a lot, I found this to be the least intrusive
way while having tolerable readability, it'd be great if someone has a
better idea.

> 
> > +        asid = cfg->asid;
> > +        stage = cfg->stage;
> > +        cfg->asid = -1;
> > +        cfg->stage = SMMU_STAGE_2;
> > +    }
> >  
> >      cached_entry = smmu_translate(bs, cfg, addr, flag, &ptw_info);
> > +
> > +    if (S2_only) {
> > +        cfg->asid = asid;
> > +        cfg->stage = stage;
> > +    }
> > +
> >      if (!cached_entry) {
> >          /* All faults from PTW has S2 field. */
> >          event->u.f_walk_eabt.s2 = (ptw_info.stage == SMMU_STAGE_2);
> > @@ -855,7 +905,7 @@ static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, 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.class = class;
> >                  event->u.f_translation.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -864,7 +914,7 @@ static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, 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_addr_size.class = SMMU_CLASS_IN;
> > +                event->u.f_addr_size.class = class;
> >                  event->u.f_addr_size.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -873,7 +923,7 @@ static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, 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_access.class = SMMU_CLASS_IN;
> > +                event->u.f_access.class = class;
> >                  event->u.f_access.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -882,7 +932,7 @@ static SMMUTranslationStatus smmuv3_do_translate(SMMUv3State *s, 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_permission.class = SMMU_CLASS_IN;
> > +                event->u.f_permission.class = class;
> >                  event->u.f_permission.rnw = flag & 0x1;
> >              }
> >              break;
> > @@ -943,15 +993,15 @@ static IOMMUTLBEntry smmuv3_translate(IOMMUMemoryRegion *mr, hwaddr addr,
> >          goto epilogue;
> >      }
> >  
> > -    status = smmuv3_do_translate(s, addr, cfg, &event, flag, &cached_entry);
> > +    status = smmuv3_do_translate(s, addr, cfg, &event, flag,
> > +                                 &cached_entry, SMMU_CLASS_IN);
> >  
> >  epilogue:
> >      qemu_mutex_unlock(&s->mutex);
> >      switch (status) {
> >      case SMMU_TRANS_SUCCESS:
> >          entry.perm = cached_entry->entry.perm;
> > -        entry.translated_addr = cached_entry->entry.translated_addr +
> > -                                    (addr & cached_entry->entry.addr_mask);
> > +        entry.translated_addr = CACHED_ENTRY_TO_ADDR(cached_entry, addr);
> >          entry.addr_mask = cached_entry->entry.addr_mask;
> >          trace_smmuv3_translate_success(mr->parent_obj.name, sid, addr,
> >                                         entry.translated_addr, entry.perm,
> > diff --git a/include/hw/arm/smmu-common.h b/include/hw/arm/smmu-common.h
> > index 96eb017e50..09d3b9e734 100644
> > --- a/include/hw/arm/smmu-common.h
> > +++ b/include/hw/arm/smmu-common.h
> > @@ -37,6 +37,9 @@
> >  #define VMSA_IDXMSK(isz, strd, lvl)         ((1ULL << \
> >                                               VMSA_BIT_LVL(isz, strd, lvl)) - 1)
> >  
> > +#define CACHED_ENTRY_TO_ADDR(ent, addr)      (ent)->entry.translated_addr + \
> > +                                             ((addr) & (ent)->entry.addr_mask);
> > +
> nit; this could be introduced in a separate patch since you have a
> caller in smmuv3_translate(). This may help the reviewer to focus on the
> most important class related changes.

Sure, I can introduce a small patch before this one with this macro.

Thanks,
Mostafa

> Besides
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> 
> Eric
> 
> >  /*
> >   * Page table walk error types
> >   */
>