[PATCH] Use hypercalls instead of accessing debug registers directly.

[PATCH] Use hypercalls instead of accessing debug registers directly.

[Arun Sharma]

Use hypercalls instead of accessing debug registers directly.

Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Arun Sharma <arun.sharma@intel.com>

--- a/linux-2.6.11-xen-sparse/arch/xen/x86_64/kernel/traps.c	Wed Jul  6 23:44:28 2005
+++ b/linux-2.6.11-xen-sparse/arch/xen/x86_64/kernel/traps.c	Thu Jul  7 14:38:19 2005
@@ -666,7 +666,7 @@
        }
 #endif
 
-	asm("movq %%db6,%0" : "=r" (condition));
+	condition = HYPERVISOR_get_debugreg(6);
 
 	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
 						SIGTRAP) == NOTIFY_STOP) {
@@ -714,7 +714,8 @@
 	info.si_addr = (void __user *)regs->rip;
 	force_sig_info(SIGTRAP, &info, tsk);	
 clear_dr7:
-	asm volatile("movq %0,%%db7"::"r"(0UL));
+	HYPERVISOR_set_debugreg(7, 0);
+
 	notify_die(DIE_DEBUG, "debug", regs, condition, 1, SIGTRAP);
 	return regs;

RE: [PATCH] Use hypercalls instead of accessing debug registers directly.

[Ian Pratt]

 

> Use hypercalls instead of accessing debug registers directly.

Is this based on measurement? If the debug registers aren't on the
critical path its probably not worth the change. If they are, they
should probably be part of a multicall.

Best,
Ian

> Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
> Signed-off-by: Arun Sharma <arun.sharma@intel.com>
> 
> --- a/linux-2.6.11-xen-sparse/arch/xen/x86_64/kernel/traps.c	
> Wed Jul  6 23:44:28 2005
> +++ b/linux-2.6.11-xen-sparse/arch/xen/x86_64/kernel/traps.c	
> Thu Jul  7 14:38:19 2005
> @@ -666,7 +666,7 @@
>         }
>  #endif
>  
> -	asm("movq %%db6,%0" : "=r" (condition));
> +	condition = HYPERVISOR_get_debugreg(6);
>  
>  	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
>  						SIGTRAP) == 
> NOTIFY_STOP) {
> @@ -714,7 +714,8 @@
>  	info.si_addr = (void __user *)regs->rip;
>  	force_sig_info(SIGTRAP, &info, tsk);	
>  clear_dr7:
> -	asm volatile("movq %0,%%db7"::"r"(0UL));
> +	HYPERVISOR_set_debugreg(7, 0);
> +
>  	notify_die(DIE_DEBUG, "debug", regs, condition, 1, SIGTRAP);
>  	return regs;
>  
> 

Re: [PATCH] Use hypercalls instead of accessing debug registers directly.

[Arun Sharma]

Ian Pratt wrote:
>  
> 
> 
>>Use hypercalls instead of accessing debug registers directly.
> 
> 
> Is this based on measurement? If the debug registers aren't on the
> critical path its probably not worth the change. If they are, they
> should probably be part of a multicall.

It's not on the critical path. We probably should just emulate the 
instruction on the GP fault.

	-Arun

Re: [PATCH] Use hypercalls instead of accessing debug registers directly.

[Keir Fraser]

On 8 Jul 2005, at 00:38, Arun Sharma wrote:

>>> Use hypercalls instead of accessing debug registers directly.
>> Is this based on measurement? If the debug registers aren't on the
>> critical path its probably not worth the change. If they are, they
>> should probably be part of a multicall.
>
> It's not on the critical path. We probably should just emulate the 
> instruction on the GP fault.

I've now added the emulation.

  -- keir