On 12/05/2011 04:01 PM, Peter Maydell wrote:
> On 5 December 2011 13:40, Avi Kivity <a...@redhat.com> wrote:
> > On 12/05/2011 01:01 PM, Peter Maydell wrote:
> >> @@ -2677,7 +2674,11 @@ void
> >> cpu_register_physical_memory_log(target_phys_addr_t start_addr,
> >> if (phys_offset == IO_MEM_UNASSIGNED) {
> >> region_offset = start_addr;
> >> }
> >> - region_offset &= TARGET_PAGE_MASK;
> >> + /* Adjust the region offset to account for the start_addr possibly
> >> + * not being page aligned, so we end up passing the IO functions
> >> + * the true offset from the start of the region.
> >> + */
> >> + region_offset -= (start_addr & ~TARGET_PAGE_MASK);
> >> size = (size + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK;
> >> end_addr = start_addr + (target_phys_addr_t)size;
> >>
> >
> > region_offset is added to iotlb in tlb_set_page(), smashing the low bits
> > with your change. It's safe in subpage, since that doesn't happen there.
>
> OK, but we only need to avoid trashing the bottom 5 bits, right?
All TARGET_PAGE_BITS of them.
> So we could do
> region_offset -= (start_addr & ~TARGET_PAGE_MASK);
> if (size >= TARGET_PAGE_SIZE) {
> region_offset &= ~0x1F; /* can make this a #define IO_MEM_MASK */
> }
>
> which would allow regions to start on 0x20 granularity, or byte granularity
> if they're less than a page in size (and so guaranteed to be subpages only).
>
An alternative is to stash region_offset somewhere else. There's
CPUTLBEntry::addend, see comment above its definition.
--
error compiling committee.c: too many arguments to function
