On Fri, Sep 27, 2019 at 10:29:21AM +0200, Paul Durrant wrote: > > -----Original Message----- > > From: Roger Pau Monne <[email protected]> > > Sent: 26 September 2019 16:07 > > To: Paul Durrant <[email protected]> > > Cc: [email protected]; Ian Jackson <[email protected]>; > > Wei Liu <[email protected]>; Andrew > > Cooper <[email protected]>; George Dunlap > > <[email protected]>; Jan Beulich > > <[email protected]>; Julien Grall <[email protected]>; Konrad Rzeszutek > > Wilk > > <[email protected]>; Stefano Stabellini <[email protected]>; Tim > > (Xen.org) <[email protected]> > > Subject: Re: [PATCH v2 09/11] vpci: register as an internal ioreq server > > > > On Tue, Sep 10, 2019 at 03:49:41PM +0200, Paul Durrant wrote: > > > > -----Original Message----- > > > > From: Roger Pau Monne <[email protected]> > > > > Sent: 03 September 2019 17:14 > > > > To: [email protected] > > > > Cc: Roger Pau Monne <[email protected]>; Ian Jackson > > > > <[email protected]>; Wei Liu > > > > <[email protected]>; Andrew Cooper <[email protected]>; George > > > > Dunlap <[email protected]>; > > Jan > > > > Beulich <[email protected]>; Julien Grall <[email protected]>; > > > > Konrad Rzeszutek Wilk > > > > <[email protected]>; Stefano Stabellini <[email protected]>; > > > > Tim (Xen.org) > > <[email protected]>; > > > > Paul Durrant <[email protected]> > > > > Subject: [PATCH v2 09/11] vpci: register as an internal ioreq server > > > > @@ -478,6 +480,67 @@ void vpci_write(pci_sbdf_t sbdf, unsigned int reg, > > > > unsigned int size, > > > > spin_unlock(&pdev->vpci->lock); > > > > } > > > > > > > > +#ifdef __XEN__ > > > > +static int ioreq_handler(struct vcpu *v, ioreq_t *req, void *data) > > > > +{ > > > > + pci_sbdf_t sbdf; > > > > + > > > > + if ( req->type == IOREQ_TYPE_INVALIDATE ) > > > > + /* > > > > + * Ignore invalidate requests, those can be received even > > > > without > > > > + * having any memory ranges registered, see > > > > send_invalidate_req. > > > > + */ > > > > + return X86EMUL_OKAY; > > > > > > In general, I wonder whether internal servers will ever need to deal with > > > invalidate? The code only > > exists to get QEMU to drop its map cache after a decrease_reservation so > > that the page refs get > > dropped. > > > > I think the best solution here is to rename hvm_broadcast_ioreq to > > hvm_broadcast_ioreq_external and switch it's callers. Both > > send_timeoffset_req and send_invalidate_req seem only relevant to > > external ioreq servers. > > send_timeoffset_req() is relic which ought to be replaced with another > mechanism IMO... > > When an HVM guest writes its RTC, a new 'timeoffset' value (offset of RTC > from host time) is calculated (also applied to the PV wallclock) and > advertised via this ioreq. In XenServer, this is picked up by QEMU, forwarded > via QMP to XAPI and then written into the VM meta-data (which than causes it > to be written into xenstore too). All this is so that that guest's RTC can be > set correctly when it is rebooted... There has to be a better way (e.g. > extracting RTC via hvm context and saving it before cleaning up the domain). > > send_invalidate_req() is relevant for any emulator maintaining a cache of > guest->host memory mappings which, I guess, could include internal emulators > even if this is not the case at the moment.
Maybe, but I would expect an internal emulator to get a reference on the gfn if it does need to keep it in some kind of cache, or else I don't think code in the hypervisor should be keeping such references. IMO I would start by not forwarding invalidate requests to internal emulators. We can always change this in the future if we come up with a use-cases that needs it. Thanks, Roger. _______________________________________________ Xen-devel mailing list [email protected] https://lists.xenproject.org/mailman/listinfo/xen-devel
