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

[David Hildenbrand]

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

--
Thanks,

David / dhildenb