[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Xen hiding thermal capabilities from Dom0
On 21.11.19 14:39, Rishi wrote: On Tue, Nov 19, 2019 at 2:47 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:On 19.11.2019 06:23, Rishi wrote:ok, thanks for clearing it up. Would a patch be accepted if this option of showing EAX leaf is selectively done through command line (default disabled)?In general I'd expect this to be rather unlikely, but I guess much would depend on the actual reasoning done in the description.On longer run, what is an expected sane model of virtualizing this? With some guidance, may be I or someone else can code to bring the functionality back.Which functionality? So far you've talked of only CPUID bits I think, without explaining at all what functionality you want to have that depends on these. In general, as said earlier, CPU management is the hypervisor's responsibility, so I'd rather not see this virtualized, but the hypervisor be put into a position of doing whatever is needed. JanThe reasoning to have EAX(0x06h) exposed to Dom0 is for Thermal and Power management. Without EAX(0x06h) Dom0 is unable to sense presence of CPU core temperature or do Thermal management - including but not limited to operating Fan speed. Dom0 has to rely on other possible ways such as ipmi or BIOS which are optionally available. You are aware that dom0 can't easily control on which _physical_ cpu it is just running? So it could easily be that you are sampling lets say 3 MSRs in a function, but you are accessing different cpus each time due to the hypervisor re-scheduling the vcpu in between. And in case you want to adjust settings you can hit another cpu again. So: no, just giving dom0 access to the management hardware isn't going to fly. You need to have a proper virtualization layer for that purpose. Juergen _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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