Re: LWP Interrupt Handler

[Keir Fraser <keir.xen@gmail.com>]

On 23/03/2012 22:03, "Wei Huang" <wei.huang2@amd.com> wrote:

> I am adding interrupt support for LWP, whose spec is available at
> http://support.amd.com/us/Processor_TechDocs/43724.pdf. Basically OS can
> specify an interrupt vector in LWP_CFG MSR; the interrupt will be
> triggered when event buffer overflows. For HVM guests, I want to
> re-inject this interrupt back into the guest VM. Here is one idea
> similar to virtualized PMU: It first registers a special interrupt
> handler (say on vector 0xf6) using set_intr_gate(). When triggered, this
> handler injects an IRQ (with vector copied from LWP_CFG) into guest VM
> via virtual local APIC. This worked from my test.
> 
> But adding a interrupt handler seems to be an overkill. Is there any
> better way to create a dummy interrupt receiver on be-behalf of guest
> VMs? I also looked into IRQ and MSI solutions inside Xen. But most of
> them assume that interrupts are from physical device (but not in this
> LWP case, where interrupt is initiated from CPU itself); so they don't
> fit very well.

I think just allocating a vector is fine. If we get too many we could move
to dynamic allocation of them.

 -- Keir

> Thanks,
> -Wei
> 
>