tpuproxy: resolve FIXMEs added by cl/723723714 #11453
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- Remove the ability to mmap VFIO group FDs. As mentioned by the deleted FIXME, this is consistent with Linux. - Use MemoryTypeUncached for VFIO_GROUP_GET_DEVICE_FD FDs. On the KVM platform, this ensures that e.g. writes to memory-mapped device registers occur in program order and without combining, and no reads are cached or issued speculatively. On other platforms, this has no effect since application page table entries are controlled by the host Linux kernel. (Technically, on the KVM platform, this also has no effect on Intel CPUs for reasons described in gvisor.dev/issue/11436.) PiperOrigin-RevId: 724512151
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tpuproxy: resolve FIXMEs added by cl/723723714
Remove the ability to mmap VFIO group FDs. As mentioned by the deleted FIXME,
this is consistent with Linux.
Use MemoryTypeUncached for VFIO_GROUP_GET_DEVICE_FD FDs. On the KVM platform,
this ensures that e.g. writes to memory-mapped device registers occur in
program order and without combining, and no reads are cached or issued
speculatively. On other platforms, this has no effect since application page
table entries are controlled by the host Linux kernel. (Technically, on the
KVM platform, this also has no effect on Intel CPUs for reasons described in
gvisor.dev/issue/11436.)