Re: [PATCH 2/2] hw/arm/smmu-common: Fix TTB1 handling

[Jean-Philippe Brucker]

On Mon, Feb 13, 2023 at 05:30:03PM +0100, Eric Auger wrote:
> Hi Jean,
> 
> On 2/10/23 17:37, Jean-Philippe Brucker wrote:
> > Addresses targeting the second translation table (TTB1) in the SMMU have
> > all upper bits set (except for the top byte when TBI is enabled). Fix
> > the TTB1 check.
> >
> > Reported-by: Ola Hugosson <ola.hugosson@arm.com>
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > ---
> >  hw/arm/smmu-common.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
> > index 2b8c67b9a1..0a5a60ca1e 100644
> > --- a/hw/arm/smmu-common.c
> > +++ b/hw/arm/smmu-common.c
> > @@ -249,7 +249,7 @@ SMMUTransTableInfo *select_tt(SMMUTransCfg *cfg, 
> > dma_addr_t iova)
> >          /* there is a ttbr0 region and we are in it (high bits all zero) */
> >          return &cfg->tt[0];
> >      } else if (cfg->tt[1].tsz &&
> > -           !extract64(iova, 64 - cfg->tt[1].tsz, cfg->tt[1].tsz - 
> > tbi_byte)) {
> > +        sextract64(iova, 64 - cfg->tt[1].tsz, cfg->tt[1].tsz - tbi_byte) 
> > == -1) {
> >          /* there is a ttbr1 region and we are in it (high bits all one) */
> >          return &cfg->tt[1];
> >      } else if (!cfg->tt[0].tsz) {
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> 
> While reading the spec again, I noticed we do not support VAX. Is it
> something that we would need to support?

I guess it would be needed to support sharing page tables with the CPU, if
the CPU supports and the OS uses FEAT_LVA. But in order to share the
stage-1, Linux would need more complex features as well (ATS+PRI/Stall,
PASID).

For a private DMA address space, I think 48 bits of VA is already plenty.

Thanks,
Jean