Re: [Xen-devel] [PATCH RFC] hvm: Allow triple fault to imply crash rather than reboot

["Xuquan (Quan Xu)" <xuquan8@xxxxxxxxxx>]

On Feb 4, 2013, 6:25 AM, <andrew.cooper3@citrix> wrote:
> While the triple fault action on native hardware will result in a system
> reset, any modern operating system can and will make use of less violent
> reboot methods. As a result, the most likely cause of a triple fault is a
> fatal software bug.
>
> This patch allows the toolstack to indicate that a triple fault should mean a
> crash rather than a reboot. The default of reboot still remains the same.
>

hi, Andrew

this email has been ages ago. I am working for a triple fault related issues, 
and I have some doubts:

1)  as you mentioned here, 'fatal software bug', is it to xen hypervisor or 
guest os?
2)  why introduce 'crash'?  would the 'reboot' lead to a fatal problem ( i.e, 
xen hypervisor panic) ?
3)  are there any differences between __'crash the guest, destroy the guest , 
create the guest again'__
    And __'reboot guest'__ ?
4)  any ideas to reproduce triple fault?

Thanks
Quan



> Signed-off-by: Andrew Cooper <andrew.cooper3 [at] citrix>
>
> diff -r 5af4f2ab06f3 -r 6f8c532df545 xen/arch/x86/hvm/hvm.c
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -1233,9 +1233,14 @@ void hvm_hlt(unsigned long rflags)
> void hvm_triple_fault(void)
> {
> struct vcpu *v = current;
> + struct domain * d = v->domain;
> + u8 reason = d->arch.hvm_domain.params[HVM_PARAM_TRIPLE_FAULT_CRASH]
> + ? SHUTDOWN_crash : SHUTDOWN_reboot;
> +
> gdprintk(XENLOG_INFO, "Triple fault on VCPU%d - "
> - "invoking HVM system reset.\n", v->vcpu_id);
> - domain_shutdown(v->domain, SHUTDOWN_reboot);
> + "invoking HVM system %s.\n", v->vcpu_id,
> + reason == SHUTDOWN_crash ? "crash" : "reboot");
> + domain_shutdown(v->domain, reason);
> }
>
> void hvm_inject_trap(struct hvm_trap *trap)
> diff -r 5af4f2ab06f3 -r 6f8c532df545 xen/include/public/hvm/params.h
> --- a/xen/include/public/hvm/params.h
> +++ b/xen/include/public/hvm/params.h
> @@ -142,6 +142,9 @@
> #define HVM_PARAM_ACCESS_RING_PFN 28
> #define HVM_PARAM_SHARING_RING_PFN 29
>
> -#define HVM_NR_PARAMS 31
> +/* Boolean: Should a triple fault imply crash rather than reboot? */
> +#define HVM_PARAM_TRIPLE_FAULT_CRASH 31
> +
> +#define HVM_NR_PARAMS 32
>
> #endif /* __XEN_PUBLIC_HVM_PARAMS_H__ */

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