Re: [Xen-devel] [PATCH v5] interrupts: allow guest to set/clear MSI-X mask bit

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.08.13 at 16:03, Joby Poriyath <joby.poriyath@xxxxxxxxxx> wrote:
> Guest needs the ability to enable and disable MSI-X interrupts
> by setting the MSI-X control bit, for a passed-through device.
> Guest is allowed to write MSI-X mask bit only if Xen *thinks*
> that mask is clear (interrupts enabled). If the mask is set by
> Xen (interrupts disabled), writes to mask bit by the guest is
> ignored.
> 
> Currently, a write to MSI-X mask bit by the guest is silently
> ignored.
> 
> A likely scenario is where we have a 82599 SR-IOV nic passed
> through to a guest. From the guest if you do
> 
>   ifconfig <ETH_DEV> down
>   ifconfig <ETH_DEV> up
> 
> the interrupts remain masked. On VF reset, the mask bit is set
> by the controller. At this point, Xen is not aware that mask is set.
> However, interrupts are enabled by VF driver by clearing the mask
> bit by writing directly to BAR3 region containing the MSI-X table.
> 
> From dom0, we can verify that
> interrupts are being masked using 'xl debug-keys M'.
> 
> Initially, guest was allowed to modify MSI-X bit.
> Later this behaviour was changed.
> See changeset 74c213c506afcd74a8556dd092995fd4dc38b225.
> 
> Signed-off-by: Joby Poriyath <joby.poriyath@xxxxxxxxxx>
> ---

You should start getting used to describe the changes compared
to at least the most recent previous revision here.

> @@ -328,7 +358,8 @@ const struct hvm_mmio_handler msixtbl_mmio_handler = {
>  static void add_msixtbl_entry(struct domain *d,
>                                struct pci_dev *pdev,
>                                uint64_t gtable,
> -                              struct msixtbl_entry *entry)
> +                              struct msixtbl_entry *entry,
> +                              struct pirq *pirq)

Sill missing the const here (this is where Andrew had pointed it out
initially, the other change above just is a necessary consequence).

Jan


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