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Re: [Qemu-devel] [PATCH 4/6] exec: Factor out cpu_watchpoint_address_mat
From: |
David Hildenbrand |
Subject: |
Re: [Qemu-devel] [PATCH 4/6] exec: Factor out cpu_watchpoint_address_matches |
Date: |
Wed, 28 Aug 2019 23:54:56 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 28.08.19 23:28, Richard Henderson wrote:
> 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...
And for anything that is not a hit, we have to walk all watchpoints
either way, so the speedup would most probably be neglectable.
--
Thanks,
David / dhildenb
- [Qemu-devel] [PATCH 0/6] exec: Cleanup watchpoints, Richard Henderson, 2019/08/24
- [Qemu-devel] [PATCH 3/6] cputlb: Fold TLB_RECHECK into TLB_INVALID_MASK, Richard Henderson, 2019/08/24
- [Qemu-devel] [PATCH 5/6] cputlb: Handle watchpoints via TLB_WATCHPOINT, Richard Henderson, 2019/08/24
- [Qemu-devel] [PATCH 6/6] tcg: Check for watchpoints in probe_write(), Richard Henderson, 2019/08/24
- Re: [Qemu-devel] [PATCH 0/6] exec: Cleanup watchpoints, Richard Henderson, 2019/08/28