Re: [Xen-devel] NMI handling in HVM

[Keir Fraser <keir@xxxxxxx>]

Change needed to avoid getting a real NMI while handling the fake NMI
created by calling do_nmi() directly. It's a very valid fix.

You'll have to fix this subsequent issue by having a per-cpu bool_t exposed
from self_nmi():
 ...
 this_cpu(is_self_nmi) = 1;
 apic_icr_write(APIC_DM_NMI...);
 this_cpu(is_self_nmi) = 0;
 ...

You can check that flag from your NMI handler and if set, and current vcpu
is non-idle, you can go at guest_cpu_user_regs() to get the appropriate cpu
context for profiling. You could even do that check in the generic NMI
handler/dispatcher, and change the regs pointer you pass to the currently
registered specific NMI handler.

 -- Keir

On 31/12/2010 01:37, "Lv, Hui" <hui.lv@xxxxxxxxx> wrote:

> Dear all
>                 I saw a change about NMI handling in C/S 20059. So could
> anyone tell me what¹s the difference of these two ways?  We found that after
> changing to ?self_nmi()¹, xenoprofile cannot work correctly. Since
> ?self_nmi()¹ issue a hypervisor nmi and there is no change for xenoprofile to
> record HVM guest regs information.
> --- a/xen/arch/x86/hvm/vmx/vmx.c      Fri Aug 14 10:57:24 2009 +0100
> +++ b/xen/arch/x86/hvm/vmx/vmx.c      Fri Aug 14 10:58:32 2009 +0100
> @@ -945,8 +945,6 @@ static void vmx_enable_rdtsc_exiting(str
>     vmx_vmcs_exit(v);
>   }
>  
> -void do_nmi(struct cpu_user_regs *);
> -
>  static void vmx_init_hypercall_page(struct domain *d, void *hypercall_page)
>  {
>      char *p;
> @@ -2470,7 +2468,7 @@ asmlinkage void vmx_vmexit_handler(struc
>                  (X86_EVENTTYPE_NMI << 8) )
>                 goto exit_and_crash;
>             HVMTRACE_0D(NMI);
> -           do_nmi(regs); /* Real NMI, vector 2: normal processing. */
> +           self_nmi(); /* Real NMI, vector 2: normal processing. */
>             break;
>         case TRAP_machine_check:
>             HVMTRACE_0D(MCE);
>  
>  
> Best regards!
> Lv,hui
>  
> 
> 
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