> >>> struct pv_cpu_ops pv_cpu_ops; > >>> > >>> [only end up using cpuid. This one is a tricky one. We could > >>> arguable remove it but it does do some filtering - for example > >>> THERM is turned off, or MWAIT if a certain hypercall tells us > >>> to > >>> disable that. Since this is now a trapped operation this could > >>> be > >>> handled in the hypervisor - but then it would be in charge of > >>> filtering certain CPUID - and this is at bootup - so there is > >>> not > >>> user interaction. This needs a bit more of thinking] > >>> > >> read_msr/write_msr in this one make all msr accesses safe. IIRC there > >> are MSRs that Linux uses without checking cpuid bits. > >> IA32_PERF_CAPABILITIES for instance is used without checking PDCM bit. > > > > Right, those are needed as well. Completly forgot about them. > > CPUID is not too bad. RDMSR/WRMSR is actually worse since there are > some MSRs which are performance-critical. The really messy pvops are > the memory-related ones, as they don't match the hardware behavior.
Would you have a by any chance a nice test-case to demonstrate the rdmsr/wrmsr paths which performance-critical under baremetal? > > Similarly, beyond pvops, what new assumptions does this code add to the > code base? We have not yet narrowed down on how to "negotiate" the GDT values - as the VMX code in the hypervisor has setup those before it loads the kernel. I think Mukesh was thinking to extend the .Xen.note to enumerate some of the ones that are needed and somehow the hypervisor slurps them in. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
