Re: [PATCH v6 12/19] vfio-user: IOMMU support for remote device

[Stefan Hajnoczi]

On Mon, Feb 28, 2022 at 07:54:38PM +0000, Jag Raman wrote:
> 
> 
> > On Feb 22, 2022, at 5:40 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > 
> > On Thu, Feb 17, 2022 at 02:48:59AM -0500, Jagannathan Raman wrote:
> >> +struct RemoteIommuElem {
> >> +    AddressSpace  as;
> >> +    MemoryRegion  mr;
> >> +};
> >> +
> >> +GHashTable *remote_iommu_elem_by_bdf;
> > 
> > A mutable global hash table requires synchronization when device
> > emulation runs in multiple threads.
> > 
> > I suggest using pci_setup_iommu()'s iommu_opaque argument to avoid the
> > global. If there is only 1 device per remote PCI bus, then there are no
> > further synchronization concerns.
> 
> OK, will avoid the global. We would need to access the hash table
> concurrently since there could be more than one device in the
> same bus - so a mutex would be needed here.

I thought the PCIe topology can be set up with a separate buf for each
x-vfio-user-server? I remember something like that in the previous
revision where a root port was instantiated for each x-vfio-user-server.

Stefan

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