[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 0/1] Introduce VCPUOP_reset_vcpu_info
On Wed, Aug 06, 2014 at 03:09:43PM +0100, Jan Beulich wrote: > >>> On 06.08.14 at 15:08, <vkuznets@xxxxxxxxxx> wrote: > > --- a/arch/x86/xen/enlighten.c > > +++ b/arch/x86/xen/enlighten.c > > @@ -183,8 +183,6 @@ static void xen_vcpu_setup(int cpu) > > * This path is called twice on PVHVM - first during bootup via > > * smp_init -> xen_hvm_cpu_notify, and then if the VCPU is being > > * hotplugged: cpu_up -> xen_hvm_cpu_notify. > > - * As we can only do the VCPUOP_register_vcpu_info once lets > > - * not over-write its result. > > * > > * For PV it is called during restore (xen_vcpu_restore) and bootup > > * (xen_setup_vcpu_info_placement). The hotplug mechanism does not > > @@ -207,14 +205,23 @@ static void xen_vcpu_setup(int cpu) > > info.mfn = arbitrary_virt_to_mfn(vcpup); > > info.offset = offset_in_page(vcpup); > > > > + /* > > + * Call VCPUOP_reset_vcpu_info before VCPUOP_register_vcpu_info, > > this > > + * is required if we boot after kexec. > > + */ > > + > > + if (cpu != 0) { > > + err = HYPERVISOR_vcpu_op(VCPUOP_reset_vcpu_info, cpu, NULL); > > + if (err) > > + pr_warn("VCPUOP_reset_vcpu_info for CPU%d failed: > > %d\n", > > + cpu, err); > > + } > > Just for my understanding of why exactly you need the new operation: > Why is this being done here, when you already do the reset in the > cpu-die/shutdown paths? And why not for CPU 0? For CPU0 it will always error out (as we can't do the hypercall on v != current as we are doing this on an BSP path) in the hypervisor. This path could also been taken when doing a kdump instead of kexec path - hence the reset hadn't happen in the cpu-die shutdown paths. > > Furthermore, what is the state of vCPU-s beyond 31 going to be after > they got their vCPU info reset? They won't have any other area as > fallback. Yet I don't think you can now and forever guarantee that > native_cpu_die() won't do anything requiring that structure. > > Jan > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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