Messages in this thread | | | Subject | Re: [PATCH v2] vfio iommu: Add dma available capability | From | Matthew Rosato <> | Date | Mon, 14 Sep 2020 18:32:41 -0400 |
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On 9/14/20 6:25 PM, Matthew Rosato wrote: > Commit 492855939bdb ("vfio/type1: Limit DMA mappings per container") added > a limit to the number of concurrent DMA requests for a vfio container. > However, lazy unmapping in s390 can in fact cause quite a large number of > outstanding DMA requests to build up prior to being purged, potentially > the entire guest DMA space. This results in unexpected 'VFIO_MAP_DMA > failed: No space left on device' conditions seen in QEMU. > > This patch proposes to provide the remaining number of allowable DMA > requests via the VFIO_IOMMU_GET_INFO ioctl as a new capability. A > subsequent patchset to QEMU would collect this information and use it in > s390 PCI support to tap the guest on the shoulder before overrunning the > vfio limit.
Link to associated v2 QEMU patchset: https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg05067.html
> > Changes from v1: > - Report dma_avail instead of the limit, which might not have been accurate > anyway > - Text/naming changes throughout due to the above > > Matthew Rosato (1): > vfio iommu: Add dma available capability > > drivers/vfio/vfio_iommu_type1.c | 17 +++++++++++++++++ > include/uapi/linux/vfio.h | 16 ++++++++++++++++ > 2 files changed, 33 insertions(+) >
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