[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 4/4] hvmloader: add support to load extra ACPI tables from qemu
On Thu, Jan 21, 2016 at 01:23:31AM +0800, Xiao Guangrong wrote: > > > On 01/21/2016 01:18 AM, Konrad Rzeszutek Wilk wrote: > >>>>>>c) hotplug support > >>>>> > >>>>>How does that work? Ah the _DSM will point to the new ACPI NFIT for the > >>>>>OS > >>>>>to scan. That would require the hypervisor also reading this for it to > >>>>>update it's data-structures. > >>>> > >>>>Similar as you said. The NVDIMM root device in SSDT/DSDT dedicates a new > >>>>interface, > >>>>_FIT, which return the new NFIT once new device hotplugged. And yes, > >>>>domain 0 is > >>>>the better place handing this case too. > >>> > >>>That one is a bit difficult. Both the OS and the hypervisor would need to > >>>know about > >>>this (I think?). dom0 since it gets the ACPI event and needs to process > >>>it. Then > >>>the hypervisor needs to be told so it can slurp it up. > >> > >>Can dom0 receive the interrupt triggered by device hotplug? If yes, we can > >>let dom0 > > > >Yes of course it can. > >>handle all the things like native. If it can not, dom0 can interpret ACPI > >>and fetch > >>the irq info out and tell hypervior to pass the irq to dom0, it is doable? > >> > >>> > >>>However I don't know if the hypervisor needs to know all the details of an > >>>NVDIMM - or just the starting and ending ranges so that when an guest is > >>>created > >>>and the VT-d is constructed - it can be assured that the ranges are valid. > >>> > >>>I am not an expert on the P2M code - but I think that would need to be > >>>looked > >>>at to make sure it is OK with stitching an E820_NVDIMM type "MFN" into an > >>>guest PFN. > >> > >>We do better do not use "E820" as it lacks some advantages of ACPI, such > >>as, NUMA, hotplug, > >>lable support (namespace)... > > > ><hand-waves> I don't know what QEMU does for guests? I naively assumed it > >would > >create an E820_NVDIMM along with the ACPI MADT NFIT tables (and the SSDT to > >have > >the _DSM). > > Ah, ACPI eliminates this E820 entry. > > > > >Either way what I think you need to investigate is what is neccessary for the > >Xen hypervisor VT-d code (IOMMU) to have an entry which is the system > >address for > >the NVDIMM. Based on that - you will know what kind of exposure the > >hypervisor > >needs to the _FIT and NFIT tables. > > > > Interesting. I did not consider using NVDIMM as DMA. Do you have usecase for > this > kind of NVDIMM usage? An easy one is iSCSI target. You could have an SR-IOV NIC that would have TCM enabled (CONFIG_TCM_FILEIO or CONFIG_TCM_IBLOCK). Mount an file on the /dev/pmem0 (using DAX enabled FS) and export it as iSCSI LUN. The traffic would go over an SR-IOV NIC. The DMA transactions would be SR-IOV NIC <-> NVDIMM. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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