Re: [Xen-devel] [PATCH v4 15/17] x86/VPMU: NMI-based VPMU support

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 02/04/2014 11:41 AM, Jan Beulich wrote:
> > > > On 04.02.14 at 17:31, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> > On 02/04/2014 06:48 AM, Jan Beulich wrote:
> > > And then I'm still missing a reasonable level of analysis that the
> > > previously non-NMI-only interrupt handler is now safe to use in NMI
> > > context.
> > How about this?
> Looks okay, except ...
>
> > With send_guest_vcpu_virq() and hvm_get_segment_register() for PV(H) and
> > vlapic accesses for HVM moved to sofint, the only routines/macros that
> > vpmu_do_interrupt() calls in NMI mode are:
> > * memcpy()
> > * querying domain type (is_XX_domain())
> > * guest_cpu_user_regs()
> > * XLAT_cpu_user_regs()
> > * raise_softirq()
> > * vcpu_vpmu()
> > * vpmu_ops->arch_vpmu_save()
> > * vpmu_ops->do_interrupt() (in the future for PVH support)
> >
> > The latter two can only access PMU MSRs.
> ... that this additionally needs to exclude things like
> {rd,wr}msr_safe() (i.e. stuff raising exceptions that normally
> get recovered from).

I'll add that. And probably a comment in vendor-specific code to remind 
people that these routines need to be NMI-safe.

-boris

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