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Re: [Qemu-devel] [PATCH 1/2] cpu: Add callback to check architectural wa
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] cpu: Add callback to check architectural watchpoint match |
Date: |
Fri, 18 Sep 2015 14:39:56 +0100 |
On 14 September 2015 at 11:50, Sergey Fedorov <address@hidden> wrote:
> When QEMU watchpoint matches, that is not definitely an architectural
> watchpoint match yet. If it is a stop-before-access watchpoint then that
> is hardly possible to ignore it after throwing a TCG exception.
>
> A special callback is introduced to check for architectural watchpoint
> match before raising a TCG exception.
>
> Signed-off-by: Sergey Fedorov <address@hidden>
> ---
> exec.c | 5 +++++
> include/qom/cpu.h | 3 +++
> qom/cpu.c | 9 +++++++++
> 3 files changed, 17 insertions(+)
>
> diff --git a/exec.c b/exec.c
> index 54cd70a..64ed543 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1921,6 +1921,7 @@ static const MemoryRegionOps notdirty_mem_ops = {
> static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int
> flags)
> {
> CPUState *cpu = current_cpu;
> + CPUClass *cc = CPU_GET_CLASS(cpu);
> CPUArchState *env = cpu->env_ptr;
> target_ulong pc, cs_base;
> target_ulong vaddr;
> @@ -1947,6 +1948,10 @@ static void check_watchpoint(int offset, int len,
> MemTxAttrs attrs, int flags)
> wp->hitattrs = attrs;
> if (!cpu->watchpoint_hit) {
> cpu->watchpoint_hit = wp;
> + if (wp->flags & BP_CPU && !cc->debug_check_watchpoint(cpu)) {
> + cpu->watchpoint_hit = NULL;
> + continue;
> + }
> tb_check_watchpoint(cpu);
> if (wp->flags & BP_STOP_BEFORE_ACCESS) {
> cpu->exception_index = EXCP_DEBUG;
Missed this on first readthrough, but this code doesn't clear the
BP_WATCHPOINT_HIT flags from wp->flags if we decide that the
architectural watchpoint shouldn't fire. That means that next time
around when we call check_watchpoint() it might decide spruriously
that it should fire.
thanks
-- PMM