From: "Alex Bennée" <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Cc: "Alexander Bulekov" <alxndr@bu.edu>,
"Richard Henderson" <rth@twiddle.net>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: [PATCH v2] exec: flush the whole TLB if a watchpoint crosses a page boundary
Date: Wed, 3 Jun 2020 12:24:42 +0100 [thread overview]
Message-ID: <20200603112442.22833-1-alex.bennee@linaro.org> (raw)
There is no particular reason why you can't have a watchpoint in TCG
that covers a large chunk of the address space. We could be clever
about it but these cases are pretty rare and we can assume the user
will expect a little performance degradation.
NB: In my testing gdb will silently squash a watchpoint like:
watch (char[0x7fffffffff]) *0x0
to a 4 byte watchpoint. Practically it will limit the maximum size
based on max-value-size. However given enough of a tweak the sky is
the limit.
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
v2
- use cleaner in_page = -(addr | TARGET_PAGE_MASK) logic per rth
---
exec.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/exec.c b/exec.c
index 5162f0d12f9..65a4376df37 100644
--- a/exec.c
+++ b/exec.c
@@ -1036,6 +1036,7 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, vaddr len,
int flags, CPUWatchpoint **watchpoint)
{
CPUWatchpoint *wp;
+ vaddr in_page;
/* forbid ranges which are empty or run off the end of the address space */
if (len == 0 || (addr + len - 1) < addr) {
@@ -1056,7 +1057,12 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, vaddr len,
QTAILQ_INSERT_TAIL(&cpu->watchpoints, wp, entry);
}
- tlb_flush_page(cpu, addr);
+ in_page = -(addr | TARGET_PAGE_MASK);
+ if (len <= in_page) {
+ tlb_flush_page(cpu, addr);
+ } else {
+ tlb_flush(cpu);
+ }
if (watchpoint)
*watchpoint = wp;
--
2.20.1
next reply other threads:[~2020-06-03 11:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 11:24 Alex Bennée [this message]
2020-06-03 12:46 ` [PATCH v2] exec: flush the whole TLB if a watchpoint crosses a page boundary Philippe Mathieu-Daudé
2020-06-05 16:11 ` Philippe Mathieu-Daudé
2020-06-05 16:27 ` Alex Bennée
2020-06-03 16:12 ` Richard Henderson
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