[PATCH] nvme: fix bit buckets

[Keith Busch]

We can't just ignore the bit buckets since the data offsets read from
disk need to be accounted for. We could either split into multiple reads
for the actual user data requested and skip the buckets, or we could
have a place holder for bucket data. Splitting is too much over head, so
just allocate a memory region to dump unwanted data.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
This came out easier than I thought, so we can ignore my previous
feature removal patch:
  https://lists.nongnu.org/archive/html/qemu-block/2022-04/msg00398.html

 hw/nvme/ctrl.c | 9 +++++----
 hw/nvme/nvme.h | 1 +
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 03760ddeae..711c6fac29 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -845,11 +845,11 @@ static uint16_t nvme_map_sgl_data(NvmeCtrl *n, NvmeSg *sg,
         trans_len = MIN(*len, dlen);
 
         if (type == NVME_SGL_DESCR_TYPE_BIT_BUCKET) {
-            goto next;
+            addr = n->bitBucket.addr;
+        } else {
+            addr = le64_to_cpu(segment[i].addr);
         }
 
-        addr = le64_to_cpu(segment[i].addr);
-
         if (UINT64_MAX - addr < dlen) {
             return NVME_DATA_SGL_LEN_INVALID | NVME_DNR;
         }
@@ -859,7 +859,6 @@ static uint16_t nvme_map_sgl_data(NvmeCtrl *n, NvmeSg *sg,
             return status;
         }
 
-next:
         *len -= trans_len;
     }
 
@@ -6686,6 +6685,8 @@ static int nvme_init_pci(NvmeCtrl *n, PCIDevice *pci_dev, 
Error **errp)
         nvme_init_pmr(n, pci_dev);
     }
 
+    memory_region_init(&n->bitBucket, OBJECT(n), NULL, 0x100000);
+
     return 0;
 }
 
diff --git a/hw/nvme/nvme.h b/hw/nvme/nvme.h
index 739c8b8f79..d59eadc69d 100644
--- a/hw/nvme/nvme.h
+++ b/hw/nvme/nvme.h
@@ -411,6 +411,7 @@ typedef struct NvmeCtrl {
     PCIDevice    parent_obj;
     MemoryRegion bar0;
     MemoryRegion iomem;
+    MemoryRegion bitBucket;
     NvmeBar      bar;
     NvmeParams   params;
     NvmeBus      bus;
-- 
2.30.2