Re: [PATCH 3/3] hw/arm/smmuv3: Advertise support for SMMUv3.2-BBML2

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 28 Apr 2022 at 09:37, Eric Auger <eric.auger@redhat.com> wrote:
> On 4/26/22 18:04, Peter Maydell wrote:
> >  TLB invalidation correctly removes all TLB entries matching
> > the specified address or address range (unless the guest specifies the
> > leaf level explicitly, in which case it gets what it asked for). So we
> "
>
> unless the guest specifies the
> leaf level explicitly, in which case it gets what it asked for
>
> "
> This is the less obvious part as the spec says:
>
> "A TLB invalidation operation removes all matching TLB entries even if
> overlapping entries exist for a given
> address."
>
> I failed to find further precisions about the range invalidation & BBML.

If the invalidate says "level 2" then a TLB entry that wasn't
put in at level 2 doesn't match the TLB invalidate request and so
isn't removed (whether it overlaps a matching one at the same
address or not). This is defined as part of the behaviour of TLB
invalidates which specify a TTL, eg on page 142.

An implementation which did something like "find the first entry
that matches the address, then notice that it doesn't match
the specified TTL, so ignore it and do nothing" wouldn't be
correct. But "invalidate all the entries which match for
both address and TTL and ignore the ones which don't match
on TTL" is fine.

> If you are confident about this, it looks good to me.
> Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks.

-- PMM