Re: [Xen-devel] [PATCH v4 5/6] xen/x86: add PHYSDEVOP_msi_set_enable

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Sun, Mar 03, 2019 at 02:10:24AM +0100, Marek Marczykowski wrote:
> On Thu, Feb 28, 2019 at 01:25:50PM +0100, Marek Marczykowski wrote:
> > On Thu, Feb 28, 2019 at 03:58:37AM -0700, Jan Beulich wrote:
> > > Another thing: You're also bypassing the MSI{,-X}-already-enabled
> > > checks that __pci_enable_msi{,x}() do, yet allowing to enable both
> > > on a device would be a security issue.
> > 
> > Ok.
> 
> Hmm, could you explain more? Is that only the case when interrupt
> remapping is missing?

I think what Jan mentions is that the hypercall to enable MSI(-X)
should make sure PCI INTx is disabled, and prevent enabling both MSI
and MSI-X on the same device.

The device model that manages the passthrough device should already
make sure of that, but Xen should also protect itself against
bad-behaved device models when possible.

Thanks, Roger.

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