[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] cpu_down() but no cpu_up() in drivers/xen/cpu_hotplug.c ?
>-----Original Message----- >From: Jeremy Fitzhardinge [mailto:jeremy@xxxxxxxx] >Sent: Thursday, May 13, 2010 12:27 AM >To: Jiang, Yunhong >Cc: Ian Campbell; xen-devel@xxxxxxxxxxxxxxxxxxx; Jan Beulich >Subject: Re: [Xen-devel] cpu_down() but no cpu_up() in >drivers/xen/cpu_hotplug.c ? > >On 05/11/2010 08:25 PM, Jiang, Yunhong wrote: >>> Yes, it was to make it consistent with native physical CPU hotplug. It >>> also replaced some other xen-specific mechanism to allow the domain to >>> control when the cpu was actually added (I forget the details; something >>> like "cpus allowed" vs "cpus active" or something?). >>> >> I remember for cpu remove, the xen's vcpu is different to native method. In >> native, >it will only trigger a uevent to user space (at least in version like 2.6.31), >while for >xen vcpu, it will remove the vcpu directly. >> > >I would think that Xen and native are much the same; if you pull out a I suspect if native has tested the CPU hotmove. But at least from the code in container_notify_cb() at drivers/acpi/container.c, seems it will trigger a uevent to user space and the user space will take action (mostly through eiject entry under sysfs, I think). But still I don't know if this has been tested on native environment. So maybe the difference from xen vcpu does not matter. case ACPI_NOTIFY_DEVICE_CHECK: printk(KERN_WARNING "Container driver received %s event\n", (type == ACPI_NOTIFY_BUS_CHECK) ? "ACPI_NOTIFY_BUS_CHECK" : "ACPI_NOTIFY_DEVICE_CHECK"); status = acpi_bus_get_device(handle, &device); if (present) { if (ACPI_FAILURE(status) || !device) { result = container_device_add(&device, handle); if (!result) kobject_uevent(&device->dev.kobj, KOBJ_ONLINE); else printk(KERN_WARNING "Failed to add container\n"); } } else { if (ACPI_SUCCESS(status)) { /* device exist and this is a remove request */ kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE); } } >physical CPU from the system, that's in no way advisory ;) Similarly, >if you remove a vcpu from a guest, that's an external policy being >imposed onto the guest, and it doesn't get much say in the matter, >beyond being able to clean up before the vcpu goes away. > >If the domain wants to stop using a vcpu, it can simply do that by >soft-downing the vcpu, but it remains attached to the domain (again, >analogous to the native case). > > J _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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