In CoCo guests, guest memory is encrypted and untrusted (T=0) devices cannot DMA to it directly; such transfers must go through unencrypted bounce buffers. RDMA registers user pages for direct device access, bypassing the DMA layer and thus any bouncing, so registered memory does not work in this configuration. Until trusted (T=1) device detection is available, conservatively flag every device attached to a CoCo guest. Expose the condition to userspace as IB_UVERBS_DEVICE_CC_DMA_BOUNCE in device_cap_flags_ex so applications can avoid memory registration and fall back to copying buffers through send/recv.
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| @@ -1368,6 +1368,8 @@ enum ib_uverbs_device_cap_flags { · 1367 unmodified lines | ||
| 1368 | 1368 | IB_UVERBS_DEVICE_FLUSH_PERSISTENT = 1ULL << 39, |
| 1369 | 1369 | /* Atomic write attributes */ |
| 1370 | 1370 | IB_UVERBS_DEVICE_ATOMIC_WRITE = 1ULL << 40, |
| 1371 | + /* CoCo guest with DMA bounce buffering required */ | |
| 1372 | + IB_UVERBS_DEVICE_CC_DMA_BOUNCE = 1ULL << 41, | |
| 1371 | 1373 | }; |
| 1372 | 1374 | |
| 1373 | 1375 | enum ib_uverbs_raw_packet_caps { |