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?
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).
-- PMM
