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 <[email protected]> Signed-off-by: Philippe Mathieu-Daudé <[email protected]> --- block/nvme.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/block/nvme.c b/block/nvme.c index b9760ff04f..7ebd5be1f3 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[QUEUE_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; } -- 2.21.3
