Re: [RFC PATCH v3 13/18] hw/arm/smmuv3: Support nested SMMUs in smmuv3_notify_iova()

[Mostafa Saleh <smostafa@google.com>]

Hi Eric,

On Mon, May 20, 2024 at 12:37:55PM +0200, Eric Auger wrote:
> Hi Mostafa,
> 
> On 4/29/24 05:23, Mostafa Saleh wrote:
> > IOMMUTLBEvent only understands IOVA, for stage-2 only SMMUs keep
> > the implementation, while only notify for stage-1 invalidation
> > in case of nesting.
> >
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  hw/arm/smmuv3.c     | 23 +++++++++++++++--------
> >  hw/arm/trace-events |  2 +-
> >  2 files changed, 16 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> > index e0fd494646..96d07234fe 100644
> > --- a/hw/arm/smmuv3.c
> > +++ b/hw/arm/smmuv3.c
> > @@ -1051,7 +1051,7 @@ static void smmuv3_notify_iova(IOMMUMemoryRegion *mr,
> >                                 IOMMUNotifier *n,
> >                                 int asid, int vmid,
> >                                 dma_addr_t iova, uint8_t tg,
> > -                               uint64_t num_pages)
> > +                               uint64_t num_pages, int stage)
> add the new param in the doc comment above
> >  {
> >      SMMUDevice *sdev = container_of(mr, SMMUDevice, iommu);
> >      IOMMUTLBEvent event;
> > @@ -1075,14 +1075,21 @@ static void smmuv3_notify_iova(IOMMUMemoryRegion *mr,
> >              return;
> >          }
> >  
> > -        if (STAGE1_SUPPORTED(s)) {
> > +        /*
> > +         * IOMMUTLBEvent only understands IOVA, for stage-2 only SMMUs
> > +         * keep the implementation, while only notify for stage-1
> > +         * invalidation in case of nesting.
> > +         */
> > +        if (stage == SMMU_STAGE_1) {
> >              tt = select_tt(cfg, iova);
> >              if (!tt) {
> >                  return;
> >              }
> >              granule = tt->granule_sz;
> > -        } else {
> > +        } else if (!STAGE1_SUPPORTED(s)) {
> I don't get why you don't test stage == SMMU_STAGE_2 instead
> in each block shouldn't you test if the corresponding state of supported?
> >              granule = cfg->s2cfg.granule_sz;
> > +        } else {
> I don't really understand the logic here. Please can you comment each case?

The current implementation will call memory_region_notify_iommu_one()
from smmuv3_notify_iova() for stage-1 or stage-2 based on which one is supported
and in each case this address is considered an “IOVA”.

However, with nested translation memory_region_notify_iommu_one() doesn’t distinguish
between stage-1 and stage-2, so only stage-1 is considered “IOVA”.

And the implementation basically as follows:
1) If the translation was stage-1, it’s an IOVA and
   memory_region_notify_iommu_one() is called.

2) If stage-1 is not supported (this is an stage-2 only instance) maintain
   the old behaviour by calling memory_region_notify_iommu_one()

3) This leaves us with stage-1 being supported and this is a stage-2
   translation, where the notification would be ignored, I think in
   this case if the SW configured only for stage-2 it would expect
   it to behave as 2) :/

Not sure how to fix that, maybe only ignore stage-2 if it was in a nested STE,
or just or always ignore stage-2?

Thanks,
Mostafa

> 
> Thanks
> 
> Eric
> > +            return;
> >          }
> >  
> >      } else {
> > @@ -1101,7 +1108,7 @@ static void smmuv3_notify_iova(IOMMUMemoryRegion *mr,
> >  /* invalidate an asid/vmid/iova range tuple in all mr's */
> >  static void smmuv3_inv_notifiers_iova(SMMUState *s, int asid, int vmid,
> >                                        dma_addr_t iova, uint8_t tg,
> > -                                      uint64_t num_pages)
> > +                                      uint64_t num_pages, int stage)
> >  {
> >      SMMUDevice *sdev;
> >  
> > @@ -1110,10 +1117,10 @@ static void smmuv3_inv_notifiers_iova(SMMUState *s, int asid, int vmid,
> >          IOMMUNotifier *n;
> >  
> >          trace_smmuv3_inv_notifiers_iova(mr->parent_obj.name, asid, vmid,
> > -                                        iova, tg, num_pages);
> > +                                        iova, tg, num_pages, stage);
> >  
> >          IOMMU_NOTIFIER_FOREACH(n, mr) {
> > -            smmuv3_notify_iova(mr, n, asid, vmid, iova, tg, num_pages);
> > +            smmuv3_notify_iova(mr, n, asid, vmid, iova, tg, num_pages, stage);
> >          }
> >      }
> >  }
> > @@ -1144,7 +1151,7 @@ static void smmuv3_range_inval(SMMUState *s, Cmd *cmd, SMMUStage stage)
> >  
> >      if (!tg) {
> >          trace_smmuv3_range_inval(vmid, asid, addr, tg, 1, ttl, leaf, stage);
> > -        smmuv3_inv_notifiers_iova(s, asid, vmid, addr, tg, 1);
> > +        smmuv3_inv_notifiers_iova(s, asid, vmid, addr, tg, 1, stage);
> >          if (stage == SMMU_STAGE_1) {
> >              smmu_iotlb_inv_iova(s, asid, vmid, addr, tg, 1, ttl);
> >          } else {
> > @@ -1167,7 +1174,7 @@ static void smmuv3_range_inval(SMMUState *s, Cmd *cmd, SMMUStage stage)
> >          num_pages = (mask + 1) >> granule;
> >          trace_smmuv3_range_inval(vmid, asid, addr, tg, num_pages,
> >                                   ttl, leaf, stage);
> > -        smmuv3_inv_notifiers_iova(s, asid, vmid, addr, tg, num_pages);
> > +        smmuv3_inv_notifiers_iova(s, asid, vmid, addr, tg, num_pages, stage);
> >          if (stage == SMMU_STAGE_1) {
> >              smmu_iotlb_inv_iova(s, asid, vmid, addr, tg, num_pages, ttl);
> >          } else {
> > diff --git a/hw/arm/trace-events b/hw/arm/trace-events
> > index 593cc571da..be6c8f720b 100644
> > --- a/hw/arm/trace-events
> > +++ b/hw/arm/trace-events
> > @@ -55,7 +55,7 @@ smmuv3_cmdq_tlbi_s12_vmid(int vmid) "vmid=%d"
> >  smmuv3_config_cache_inv(uint32_t sid) "Config cache INV for sid=0x%x"
> >  smmuv3_notify_flag_add(const char *iommu) "ADD SMMUNotifier node for iommu mr=%s"
> >  smmuv3_notify_flag_del(const char *iommu) "DEL SMMUNotifier node for iommu mr=%s"
> > -smmuv3_inv_notifiers_iova(const char *name, int asid, int vmid, uint64_t iova, uint8_t tg, uint64_t num_pages) "iommu mr=%s asid=%d vmid=%d iova=0x%"PRIx64" tg=%d num_pages=0x%"PRIx64
> > +smmuv3_inv_notifiers_iova(const char *name, int asid, int vmid, uint64_t iova, uint8_t tg, uint64_t num_pages, int stage) "iommu mr=%s asid=%d vmid=%d iova=0x%"PRIx64" tg=%d num_pages=0x%"PRIx64" stage=%d"
> >  
> >  # strongarm.c
> >  strongarm_uart_update_parameters(const char *label, int speed, char parity, int data_bits, int stop_bits) "%s speed=%d parity=%c data=%d stop=%d"
>