[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC v2 3/6] xen/arm: Allow platform_hvc to handle guest SMC calls
On Thu, Feb 9, 2017 at 1:01 PM, Edgar E. Iglesias <edgar.iglesias@xxxxxxxxxx> wrote: > On Thu, Feb 09, 2017 at 12:42:09PM -0700, Tamas K Lengyel wrote: >> On Thu, Feb 9, 2017 at 11:39 AM, Julien Grall <julien.grall@xxxxxxx> wrote: >> > Hi Tamas, >> > >> > On 02/09/2017 06:11 PM, Tamas K Lengyel wrote: >> >> >> >> On Wed, Feb 8, 2017 at 5:08 PM, Julien Grall <julien.grall@xxxxxxx> wrote: >> >>> >> >>> On 08/02/2017 23:28, Tamas K Lengyel wrote: >> >>>> >> >>>> On Wed, Feb 8, 2017 at 3:04 PM, Julien Grall <julien.grall@xxxxxxx> >> >>>> wrote: >> >>> >> >>> You haven't understood my point. Xen is currently emulating PSCI call for >> >>> the guest to allow powering up and down the CPUs and other stuff. If you >> >>> decide to trap all the SMCs, you would have to handle them. >> >> >> >> >> >> Sure, it's more work on the monitor side, but other then that, what's >> >> the problem? >> > >> > >> > Because you will have to introduce hypercalls to get all the necessary >> > information from Xen that will not be available from outside. >> >> > Given that SMC has been designed to target different services (PSCI, >> > Trusted >> > OS...) it would be normal to have monitor app only monitoring a certain set >> > of SMC call. You cannot deny a such use case as it would avoid an monitor >> > app to handle every single call that would be consumed by XEN but not >> > forwarded to the secure firmware. >> > >> >> I have nothing against introducing a fine-tune option to the SMC >> monitoring system so the monitor app can determine if it wants all >> SMCs or only a subset. At the moment I don't know of any usecase that >> would require this option. I certainly don't need it. If this option >> gets implemented by someone, I would be happy to take it. > > Well, the reason it would be useful is the other way around. > On for example ZynqMP, enabling the monitor is useless since it will > turn off the ability to use the vital FW APIs needed for device > passthrough. > > So the monitor only works for PV guests that call SMC APIs to some > imaginary Firmware. > > While a monitor that didn't insist in consuming all SMC calls, > could very well be useful for monitoring/tracing purposes or > other stuff even with guests that actually use a "real" FW API. > > I don't think we need to implement support for the latter right away, > we can incrementally add support for these things (I hope). > Certainly, as I said I have nothing against adding such a feature. All I'm saying is that I don't know of any usecase that requires that option at the moment, so I would be OK with just making the two exclusive. If someone finds the time to implement such fine-tuning, I'm all for it. Tamas _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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