Re: [Qemu-devel] [PATCH 0/8] target-i386: Implement debug extensions

[Eduardo Habkost]

On Mon, Sep 21, 2015 at 02:05:52PM +0200, Paolo Bonzini wrote:
> 
> 
> On 15/09/2015 20:45, Richard Henderson wrote:
> > Best guess, since I can't find any code that actually uses them.
> > Linux actively turns them off at boot...
> 
> I've sent a kvm-unit-tests patch to test debug extensions.  It shows
> that debug extensions work, but the following needs to be squashed in
> patch 4:

This can't be squashed directly into patch 4/8 because patch 7/8 touches
the same code, but I have solved the conflicts manually (the resulting
tree is exactly the same). I will send the conflict resolution diffs as
replies to patches 4/8 and 7/8.

> 
> diff --git a/target-i386/bpt_helper.c b/target-i386/bpt_helper.c
> index c258598..b24e446 100644
> --- a/target-i386/bpt_helper.c
> +++ b/target-i386/bpt_helper.c
> @@ -134,14 +134,14 @@ void cpu_x86_update_dr7(CPUX86State *env, uint32_t 
> new_dr7)
>          int mod = ((old_dr7 | old_dr7 * 2) ^ (new_dr7 | new_dr7 * 2)) & 0xff;
>  
>          for (i = 0; i < DR7_MAX_BP; i++) {
> -            if (mod & (2 << i * 2)) {
> -                /* We know that register i has changed enable state;
> -                   recheck what that state should be and apply.  */
> -                if (hw_breakpoint_enabled(new_dr7, i)) {
> -                    iobpt |= hw_breakpoint_insert(env, i);
> -                } else {
> -                    hw_breakpoint_remove(env, i);
> -                }
> +            if ((mod & (2 << i * 2)) && !hw_breakpoint_enabled(new_dr7, i)) {
> +                hw_breakpoint_remove(env, i);
> +            }
> +        }
> +        env->dr[7] = new_dr7 | DR7_FIXED_1;
> +        for (i = 0; i < DR7_MAX_BP; i++) {
> +            if (mod & (2 << i * 2) && hw_breakpoint_enabled(new_dr7, i)) {
> +                iobpt |= hw_breakpoint_insert(env, i);
>              } else if (hw_breakpoint_type(new_dr7, i) == DR7_TYPE_IO_RW
>                         && hw_breakpoint_enabled(new_dr7, i)) {
>                  iobpt |= HF_IOBPT_MASK;
> 
> Otherwise, hw_breakpoint_insert doesn't work because it expects to
> see an updated env->dr[7].
> 
> There are a couple other issues that the tests expose, but they are
> not regressions so I will send patches later.
> 
> Paolo
> 

-- 
Eduardo