On Thu, Aug 25, 2011 at 08:06:34AM +0300, Pekka Enberg wrote: > On Wed, 2011-08-24 at 21:49 -0700, David Evensky wrote: > > On Wed, Aug 24, 2011 at 10:27:18PM -0500, Alexander Graf wrote: > > > > > > On 24.08.2011, at 17:25, David Evensky wrote: > > > > > > > > > > > > > > > This patch adds a PCI device that provides PCI device memory to the > > > > guest. This memory in the guest exists as a shared memory segment in > > > > the host. This is similar memory sharing capability of Nahanni > > > > (ivshmem) available in QEMU. In this case, the shared memory segment > > > > is exposed as a PCI BAR only. > > > > > > > > A new command line argument is added as: > > > > --shmem pci:0xc8000000:16MB:handle=/newmem:create > > > > > > > > which will set the PCI BAR at 0xc8000000, the shared memory segment > > > > and the region pointed to by the BAR will be 16MB. On the host side > > > > the shm_open handle will be '/newmem', and the kvm tool will create > > > > the shared segment, set its size, and initialize it. If the size, > > > > handle, or create flag are absent, they will default to 16MB, > > > > handle=/kvm_shmem, and create will be false. The address family, > > > > 'pci:' is also optional as it is the only address family currently > > > > supported. Only a single --shmem is supported at this time. > > > > > > Did you have a look at ivshmem? It does that today, but also gives > > you an IRQ line so the guests can poke each other. For something as > > simple as this, I don't see why we'd need two competing > > implementations. > > > > Isn't ivshmem in QEMU? If so, then I don't think there isn't any > > competition. How do you feel that these are competing? > > It's obviously not competing. One thing you might want to consider is > making the guest interface compatible with ivshmem. Is there any reason > we shouldn't do that? I don't consider that a requirement, just nice to > have. I think it depends on what the goal is. For us, just having a hunk of memory shared between the host and guests that the guests can ioremap provides a lot. Having the rest of ivshmem's guest interface I don't think would impact our use above, but I haven't tested things with QEMU to verify that. \dae > > Pekka > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
