On Mon, Oct 25, 2021 at 08:21:22AM -0700, Elena wrote: > On Mon, Oct 25, 2021 at 01:42:56PM +0100, Stefan Hajnoczi wrote: > > On Mon, Oct 11, 2021 at 10:34:29PM -0700, elena wrote: > > > On Wed, Nov 25, 2020 at 12:44:07PM -0800, Elena Afanasova wrote: > > > > Hello, > > > > > > > > > > Hi > > > > > > Sorry for top-posting, just wanted to provide a quik update. > > > We are currently working on the support for ioregionfd in Qemu and will > > > be posting the patches soon. Plus the KVM patches will be posted based > > > of the RFC v3 with some fixes if there are no objections from Elena's side > > > who originally posted KVM RFC patchset. > > > > Hi Elena, > > Hello Stefan. > > > I'm curious what approach you want to propose for QEMU integration. A > > while back I thought about the QEMU API. It's possible to implement it > > along the lines of the memory_region_add_eventfd() API where each > > ioregionfd is explicitly added by device emulation code. An advantage of > > this approach is that a MemoryRegion can have multiple ioregionfds, but > > I'm not sure if that is a useful feature. > > > > This is the approach that is currently in the works. Agree, I dont see > much of the application here at this point to have multiple ioregions > per MemoryRegion. > I added Memory API/eventfd approach to the vfio-user as well to try > things out. > > > An alternative is to cover the entire MemoryRegion with one ioregionfd. > > That way the device emulation code can use ioregionfd without much fuss > > since there is a 1:1 mapping between MemoryRegions, which are already > > there in existing devices. There is no need to think deeply about which > > ioregionfds to create for a device. > > > > A new API called memory_region_set_aio_context(MemoryRegion *mr, > > AioContext *ctx) would cause ioregionfd (or a userspace fallback for > > non-KVM cases) to execute the MemoryRegion->read/write() accessors from > > the given AioContext. The details of ioregionfd are hidden behind the > > memory_region_set_aio_context() API, so the device emulation code > > doesn't need to know the capabilities of ioregionfd. > > > > > The second approach seems promising if we want more devices to use > > ioregionfd inside QEMU because it requires less ioregionfd-specific > > code. > > > I like this approach as well. > As you have mentioned, the device emulation code with first approach > does have to how to handle the region accesses. The second approach will > make things more transparent. Let me see how can I modify what there is > there now and may ask further questions. Thanks, I look forward to patches you are working on! Stefan
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