Re: [PATCH resend v2 1/5] tpm: mark correct memory region range dirty when clearing RAM

[Peter Xu <peterx@redhat.com>]

On Fri, Jul 23, 2021 at 09:15:43PM +0200, David Hildenbrand wrote:
> On 23.07.21 16:52, Peter Xu wrote:
> > On Tue, Jul 20, 2021 at 03:03:00PM +0200, David Hildenbrand wrote:
> > > @@ -30,11 +30,13 @@ void tpm_ppi_reset(TPMPPI *tpmppi)
> > >           guest_phys_blocks_init(&guest_phys_blocks);
> > >           guest_phys_blocks_append(&guest_phys_blocks);
> > >           QTAILQ_FOREACH(block, &guest_phys_blocks.head, next) {
> > > +            ram_addr_t mr_start = memory_region_get_ram_addr(block->mr);
> > > +
> > >               trace_tpm_ppi_memset(block->host_addr,
> > >                                    block->target_end - block->target_start);
> > >               memset(block->host_addr, 0,
> > >                      block->target_end - block->target_start);
> > > -            memory_region_set_dirty(block->mr, 0,
> > > +            memory_region_set_dirty(block->mr, block->target_start - mr_start,
> > >                                       block->target_end - block->target_start);
> > 
> > target_start should falls in gpa range, while mr_start is ram_addr_t.  I am not
> > sure whether this is right..
> 
> When I wrote that code I was under the impression that
> memory_region_get_ram_addr() would give the GPA where the memory region
> starts, but ... that's not correct as you point out. "offset" confusion :)
> 
> > 
> > Neither do I know how to get correct mr offset with the existing info we've got
> > from GuestPhysBlock.  Maybe we need to teach guest_phys_blocks_region_add() to
> > also record section->offset_within_region?
> 
> We might actually want offset_within_address_space + offset_within_region,
> so we can calculate the GPA difference to see where inside the ramblock we
> end up.

I still think offset_within_region is exactly what we want to fill in here, but
you can do a double check.

> 
> I'll have a look next week, thanks for noticing!

Sure!

-- 
Peter Xu