On 1/30/19 6:55 AM, Paul Mackerras wrote: > On Tue, Jan 29, 2019 at 06:44:50PM +0100, Cédric Le Goater wrote: >> On 1/29/19 5:12 AM, Paul Mackerras wrote: >>> On Mon, Jan 28, 2019 at 07:26:00PM +0100, Cédric Le Goater wrote: >>>> >>>> Is clearing the PTEs and repopulating the VMA unsafe ? >>> >>> Actually, now that I come to think of it, there could be any number of >>> VMAs (well, up to almost 64k of them), since once you have a file >>> descriptor you can call mmap on it multiple times. >>> >>> The more I think about it, the more I think that getting userspace to >>> manage the mappings with mmap() and munmap() is the right idea if it >>> can be made to work. >> >> We might be able to mmap() and munmap() regions of ESB pages in the RTAS >> call "ibm,change-msi". I think that's the right spot for it. > > I was thinking that the ESB pages should be mmapped for device > interrupts at VM startup or when a device is hot-plugged in, and > munmapped when the device is hot-removed. Maybe the mmap could be > done in conjunction with the KVM_IRQFD call? > > What is the reasoning behind doing it in the ibm,change-msi call? Because when the device is plugged in, it has no interrupts. These are allocated on demand only when the driver is loaded in the guest. C.
