Re: [Qemu-devel] [PATCH 4/6] exec: Factor out cpu_watchpoint_address_matches

[Richard Henderson]

On 8/26/19 1:41 AM, David Hildenbrand wrote:
>> -    /* Make accesses to pages with watchpoints go via the
>> -       watchpoint trap routines.  */
>> -    QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
>> -        if (cpu_watchpoint_address_matches(wp, vaddr, TARGET_PAGE_SIZE)) {
>> -            /* Avoid trapping reads of pages with a write breakpoint. */
>> -            if ((prot & PAGE_WRITE) || (wp->flags & BP_MEM_READ)) {
>> -                iotlb = PHYS_SECTION_WATCH + paddr;
>> -                *address |= TLB_MMIO;
>> -                break;
> In the old code, we were able to break once we found a hit ...
> 
>> -            }
>> -        }
>> +    /* Avoid trapping reads of pages with a write breakpoint. */
>> +    match = (prot & PAGE_READ ? BP_MEM_READ : 0)
>> +          | (prot & PAGE_WRITE ? BP_MEM_WRITE : 0);
>> +    flags = cpu_watchpoint_address_matches(cpu, vaddr, TARGET_PAGE_SIZE);
>> +    if (flags & match) {
> ... now you cannot break early anymore. Maybe pass in the match to
> cpu_watchpoint_address_matches() ?

Hmm, yes, perhaps.

OTOH, summing a bitmask is a very quick operation.  Depending on the total
number of watchpoints, of course...


r~