[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 2/5] Mini-OS: get own domid
Hi, On 13/11/2023 09:28, Jan Beulich wrote: On 13.11.2023 10:12, Julien Grall wrote:On 13/11/2023 07:37, Jan Beulich wrote:On 10.11.2023 18:38, Julien Grall wrote:Hi Jan, On 10/11/2023 12:44, Jan Beulich wrote:On 10.11.2023 13:23, Roger Pau Monné wrote:On Fri, Nov 10, 2023 at 12:34:32PM +0100, Juergen Gross wrote:Get the own domid via creation of a temporary event channel. There is no "official" way to read the own domid in PV guests, so use the event channel interface to get it: - allocate an unbound event channel specifying DOMID_SELF for the other end - read the event channel status which will contain the own domid in unbound.dom - close the event channelShould we look into introducing a way to expose the domid, so that in the future we might not need to resort to this workarounds to get the domid? Maybe in the PV-specific cpuid leaf? It's a shame we didn't put it in a non-HVM specific leaf when it was made available to HVM for pvshim reasons.Couldn't we retroactively generalize the type-agnostic parts of that leaf?This would only work for x86. I think we want to have a generic hypercalls so it can be used by all arch.Hmm, yes, perhaps. Otoh it would seem desirable to me if arch-es also provided some extension to an arch-natural way of feature detection (which CPUID is on x86), without the need to invoke any hypercalls.For Arm, I can't really think of anything other than hvc/smc which are used for calls to the hypervisor/monitor (so basically hypercalls). Please suggest if you have a better idea.I don't know enough Arm to properly suggest something. Arm64 has various id_* system registers, so I would be wondering whether having a properly virtual one reserved in system register space couldn't do the trick. AFAIK there are none available. But if such exists, then I don't see how that would suit with my requests to have an arch-agnostic approach. Each architecture would need to have to provide a way to expose those values. At which point, why not using hypercall? What's wrong with it? Cheers, -- Julien Grall
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