On 6/3/20 1:24 PM, Alex Bennée wrote:
> 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 <alx...@bu.edu>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
>
> ---
> v2
> - use cleaner in_page = -(addr | TARGET_PAGE_MASK) logic per rth
Can we have a macro for this?
Maybe QEMU_IN_PAGE_OFFSET(addr, TARGET_PAGE_MASK)?
or QEMU_OFFSET_IN_PAGE()...
> ---
> 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;
>
