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[v5,08/15] block/nvme: Use union of NvmeIdCtrl / NvmeIdNs structures

Message ID 20200820165901.1139109-9-philmd@redhat.com
State Superseded
Headers show
Series block/nvme: Various cleanups required to use multiple queues | expand

Commit Message

Philippe Mathieu-Daudé Aug. 20, 2020, 4:58 p.m. UTC 
We allocate an unique chunk of memory then use it for two
different structures. By using an union, we make it clear
the data is overlapping (and we can remove the casts).

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 block/nvme.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)
diff mbox series

Patch

diff --git a/block/nvme.c b/block/nvme.c
index 99822d9fd36..2bd1935f951 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -508,9 +508,10 @@  static int nvme_cmd_sync(BlockDriverState *bs, NVMeQueuePair *q,
 static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp)
 {
     BDRVNVMeState *s = bs->opaque;
-    NvmeIdCtrl *idctrl;
-    NvmeIdNs *idns;
-    uint8_t *id;
+    union {
+        NvmeIdCtrl ctrl;
+        NvmeIdNs ns;
+    } *id;
     NvmeLBAF *lbaf;
     uint16_t oncs;
     int r;
@@ -520,14 +521,12 @@  static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp)
         .cdw10 = cpu_to_le32(0x1),
     };
 
-    id = qemu_try_blockalign0(bs, sizeof(NvmeIdCtrl));
+    id = qemu_try_blockalign0(bs, sizeof(*id));
     if (!id) {
         error_setg(errp, "Cannot allocate buffer for identify response");
         goto out;
     }
-    idctrl = (NvmeIdCtrl *)id;
-    idns = (NvmeIdNs *)id;
-    r = qemu_vfio_dma_map(s->vfio, id, sizeof(NvmeIdCtrl), true, &iova);
+    r = qemu_vfio_dma_map(s->vfio, id, sizeof(*id), true, &iova);
     if (r) {
         error_setg(errp, "Cannot map buffer for DMA");
         goto out;
@@ -539,22 +538,22 @@  static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp)
         goto out;
     }
 
-    if (le32_to_cpu(idctrl->nn) < namespace) {
+    if (le32_to_cpu(id->ctrl.nn) < namespace) {
         error_setg(errp, "Invalid namespace");
         goto out;
     }
-    s->write_cache_supported = le32_to_cpu(idctrl->vwc) & 0x1;
-    s->max_transfer = (idctrl->mdts ? 1 << idctrl->mdts : 0) * s->page_size;
+    s->write_cache_supported = le32_to_cpu(id->ctrl.vwc) & 0x1;
+    s->max_transfer = (id->ctrl.mdts ? 1 << id->ctrl.mdts : 0) * s->page_size;
     /* For now the page list buffer per command is one page, to hold at most
      * s->page_size / sizeof(uint64_t) entries. */
     s->max_transfer = MIN_NON_ZERO(s->max_transfer,
                           s->page_size / sizeof(uint64_t) * s->page_size);
 
-    oncs = le16_to_cpu(idctrl->oncs);
+    oncs = le16_to_cpu(id->ctrl.oncs);
     s->supports_write_zeroes = !!(oncs & NVME_ONCS_WRITE_ZEROS);
     s->supports_discard = !!(oncs & NVME_ONCS_DSM);
 
-    memset(id, 0, 4096);
+    memset(id, 0, sizeof(*id));
     cmd.cdw10 = 0;
     cmd.nsid = cpu_to_le32(namespace);
     if (nvme_cmd_sync(bs, s->queues[INDEX_ADMIN], &cmd)) {
@@ -562,11 +561,11 @@  static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp)
         goto out;
     }
 
-    s->nsze = le64_to_cpu(idns->nsze);
-    lbaf = &idns->lbaf[NVME_ID_NS_FLBAS_INDEX(idns->flbas)];
+    s->nsze = le64_to_cpu(id->ns.nsze);
+    lbaf = &id->ns.lbaf[NVME_ID_NS_FLBAS_INDEX(id->ns.flbas)];
 
-    if (NVME_ID_NS_DLFEAT_WRITE_ZEROES(idns->dlfeat) &&
-            NVME_ID_NS_DLFEAT_READ_BEHAVIOR(idns->dlfeat) ==
+    if (NVME_ID_NS_DLFEAT_WRITE_ZEROES(id->ns.dlfeat) &&
+            NVME_ID_NS_DLFEAT_READ_BEHAVIOR(id->ns.dlfeat) ==
                     NVME_ID_NS_DLFEAT_READ_BEHAVIOR_ZEROES) {
         bs->supported_write_flags |= BDRV_REQ_MAY_UNMAP;
     }