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Subject: Re: [PATCH v7 3/3] drivers/vfio: EEH support for VFIO PCI device
From: Alex Williamson <alex.williamson@redhat.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Tue, 27 May 2014 14:37:49 -0600
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Cc: aik@ozlabs.ru, Gavin Shan <gwshan@linux.vnet.ibm.com>,
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On Wed, 2014-05-28 at 06:30 +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2014-05-27 at 12:15 -0600, Alex Williamson wrote:
> 
> > > +/*
> > > + * Reset is the major step to recover problematic PE. The following
> > > + * command helps on that.
> > > + */
> > > +struct vfio_eeh_pe_reset {
> > > +	__u32 argsz;
> > > +	__u32 flags;
> > > +	__u32 option;
> > > +#define VFIO_EEH_PE_RESET_DEACTIVATE	0	/* Deactivate reset	*/
> > > +#define VFIO_EEH_PE_RESET_HOT		1	/* Hot reset		*/
> > > +#define VFIO_EEH_PE_RESET_FUNDAMENTAL	3	/* Fundamental reset	*/
> > 
> > How does a user know which of these to use?
> 
> The usual way is the driver asks for one or the other, this plumbs back
> into the guest EEH code which itself plumbs into the PCIe error recovery
> framework in Linux.

So magic?

> 
> However I do have a question for Gavin here: Why do we expose an
> explicit "deactivate" ? The reset functions should do the whole
> reset sequence (assertion, delay, deassertion). In fact the firmware
> doesn't really give you a choice for PERST right ? Or do we have
> a requirement to expose both phases for RTAS? (In that case I'm
> happy to ignore the deassertion there too).
> 
> Cheers,
> Ben.
>