Re: [PATCH] kvm: device-assignment: Catch GSI overflow

[Sheng Yang <sheng@linux.intel.com>]

On Friday 08 May 2009 01:16:53 Alex Williamson wrote:
> On Thu, 2009-05-07 at 11:09 -0600, Alex Williamson wrote:
> > Fix the index at which we return -ENOSPC since the kernel side will
> > reject a GSI >= KVM_MAX_IRQ_ROUTES.  Also, mask as a signed int before
> > testing for error.
>
> Even with this, there still seems to be a fundamental problem with our
> consumption of GSIs in kvm.  For example, every time a guest writes to
> the MSI capabilities area and enables MSI support, we call
> kvm_get_irq_route_gsi() to get a new max_used_gsi + 1 value, then call
> kvm_add_routing_entry(), which updates max_used_gsi.  It doesn't take
> too long before we exhaust the GSI space and the device no longer works.
> This seems to happen within a minute or two of booting a guest with an
> e1000e device sitting idle on a busy network.  Do we need to keep a
> bitmap of used GSIs or maybe just attempt to reuse the GSI we've gotten
> previously for the device?  Thanks,

Yes, I think a bitmap is much better here.

Thanks.

-- 
regards
Yang, Sheng

>
> Alex
>
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