Re: [PATCH 2/2] KVM: Use pci_store/load_saved_state() around VM device usage

[Avi Kivity <avi@redhat.com>]

On 04/18/2011 10:43 PM, Alex Williamson wrote:
> On Sun, 2011-04-17 at 12:25 +0300, Avi Kivity wrote:
> >  On 04/15/2011 10:54 PM, Alex Williamson wrote:
> >  >  Store the device saved state so that we can reload the device back
> >  >  to the original state when it's unassigned.  This has the benefit
> >  >  that the state survives across pci_reset_function() calls via
> >  >  the PCI sysfs reset interface while the VM is using the device.
> >
> >  >  @@ -516,7 +518,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
> >  >
> >  >    	pci_reset_function(dev);
> >  >    	pci_save_state(dev);
> >  >  -
> >  >  +	match->pci_saved_state = pci_store_saved_state(dev);
> >  >    	match->assigned_dev_id = assigned_dev->assigned_dev_id;
> >
> >  Error check?
> >
> >  It might be better to give up the opacity of the data structure and make
> >  pci_saved_state the full struct, not a pointer.
>
> pci_store_saved_state() returns NULL on error, which is correctly
> handled if we pass NULL to pci_load_saved_state() or a pointer to NULL
> to pci_load_and_free_saved_state().

But we silently swallow an error, this isn't good.

>    This is also why I changed the
> __pci_reset_function() back to a normal pci_reset_function(), so we're
> never left with an uninitialized device like we are now.
>
> We could be more verbose or return an error here, but we've gone for a
> long time not even doing this save/restore across VM usage, so I don't
> think it's worthy of preventing the device attachment if it fails.

At least a log?

Note avoiding the pointer would have removed the problem altogether.

-- 
error compiling committee.c: too many arguments to function