Re: [PATCH] tcg: gdbstub: Fix missing breakpoint issue

[Richard Henderson]

On 1/24/20 2:17 AM, Changbin Du wrote:
> When inserting breakpoints, we need to invalidate related TBs to apply
> helper call. This is done by breakpoint_invalidate(). But many users
> found the BPs sometimes never hit.
> 
> In system mode emulation, the BPs are global in guest but not particular
> address space. The issue is that the current implementation only trys to
> invalidate TB of paddr corresponding to the target vaddr in current MMU
> context. Then some cached TBs continue running without BPs applied.
> 
> To fix this issue, we can just invalidate all TBs as what step mode does.
> (For old version users, issuing a step command can workaround this problem.)
> 
> Signed-off-by: Changbin Du <address@hidden>
> ---
>  exec.c | 29 +----------------------------
>  1 file changed, 1 insertion(+), 28 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 67e520d18e..9d9fd48519 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -997,36 +997,9 @@ static void breakpoint_invalidate(CPUState *cpu, 
> target_ulong pc)
>      tb_invalidate_phys_addr(pc);
>  }
>  #else
> -void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs)

You can't remove this function yet.
You should have seen that xtensa-softmmu no longer builds.

I've cc'd you into Max Filippov's thread that addresses the same problem, and
I'm going to apply his fix for now.


r~

> -{
> -    ram_addr_t ram_addr;
> -    MemoryRegion *mr;
> -    hwaddr l = 1;
> -
> -    if (!tcg_enabled()) {
> -        return;
> -    }
> -
> -    RCU_READ_LOCK_GUARD();
> -    mr = address_space_translate(as, addr, &addr, &l, false, attrs);
> -    if (!(memory_region_is_ram(mr)
> -          || memory_region_is_romd(mr))) {
> -        return;
> -    }
> -    ram_addr = memory_region_get_ram_addr(mr) + addr;
> -    tb_invalidate_phys_page_range(ram_addr, ram_addr + 1);
> -}
> -
>  static void breakpoint_invalidate(CPUState *cpu, target_ulong pc)
>  {
> -    MemTxAttrs attrs;
> -    hwaddr phys = cpu_get_phys_page_attrs_debug(cpu, pc, &attrs);
> -    int asidx = cpu_asidx_from_attrs(cpu, attrs);
> -    if (phys != -1) {
> -        /* Locks grabbed by tb_invalidate_phys_addr */
> -        tb_invalidate_phys_addr(cpu->cpu_ases[asidx].as,
> -                                phys | (pc & ~TARGET_PAGE_MASK), attrs);
> -    }
> +    tb_flush(cpu);
>  }
>  #endif
>  
>