Hi Peter, On 6/25/20 5:15 PM, Peter Maydell wrote: > On Thu, 11 Jun 2020 at 17:15, Eric Auger <eric.au...@redhat.com> wrote: >> >> Compute the starting level on CD decoding and store it >> into SMMUTransTableInfo. We will need this information >> on IOTLB lookup so let's avoid to recompute it each time. >> >> Signed-off-by: Eric Auger <eric.au...@redhat.com> > >> --- a/hw/arm/smmu-common.c >> +++ b/hw/arm/smmu-common.c >> @@ -224,7 +224,7 @@ static int smmu_ptw_64(SMMUTransCfg *cfg, >> granule_sz = tt->granule_sz; >> stride = granule_sz - 3; >> inputsize = 64 - tt->tsz; >> - level = 4 - (inputsize - 4) / stride; >> + level = tt->starting_level; > > "4 - (x - 4) / y" doesn't really seem like it's complicated > enough to be worth caching given everything else we do on > a page table walk. Do you have perf figures to indicate that > this change is worthwhile?
no I don't have any figure or any setup at the moment to perform that bench. I thought it could only help, was not complicated to store and was of the same kind as the granule size, the input range, ... already stored in SMMUTransTableInfo. Thanks Eric > > thanks > -- PMM >
