[PATCH] nvme: Only allocate one dma bounce buffer for all nvme drives

[Kevin O'Connor]

There is no need to create multiple dma bounce buffers as the BIOS
disk code isn't reentrant capable.

Signed-off-by: Kevin O'Connor

---

This is a minor cleanup on top of the previous nvme code series.

-Kevin

--- 
src/hw/nvme-int.h |  3 ---
 src/hw/nvme.c     | 14 +++++++++-----
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h
index f0d717d..f9c807e 100644
--- a/src/hw/nvme-int.h
+++ b/src/hw/nvme-int.h
@@ -117,9 +117,6 @@ struct nvme_namespace {
     u32 block_size;
     u32 metadata_size;
     u32 max_req_size;
-
-    /* Page aligned buffer of size NVME_PAGE_SIZE. */
-    char *dma_buffer;
 };

/* Data structures for NVMe admin identify commands */
diff --git a/src/hw/nvme.c b/src/hw/nvme.c
index 39b9138..0ba981c 100644
--- a/src/hw/nvme.c
+++ b/src/hw/nvme.c
@@ -20,6 +20,9 @@
 #include "nvme.h"
 #include "nvme-int.h"

+// Page aligned "dma bounce buffer" of size NVME_PAGE_SIZE in high memory
+static void *nvme_dma_buffer;
+
 static void *
 zalloc_page_aligned(struct zone_s *zone, u32 size)
 {
@@ -294,7 +297,8 @@ nvme_probe_ns(struct nvme_ctrl *ctrl, u32 ns_idx, u8 mdts)
         ns->max_req_size = -1U;
     }

-    ns->dma_buffer = zalloc_page_aligned(&ZoneHigh, NVME_PAGE_SIZE);
+    if (!nvme_dma_buffer)
+        nvme_dma_buffer = zalloc_page_aligned(&ZoneHigh, NVME_PAGE_SIZE);

char *desc = znprintf(MAXDESCSIZE, "NVMe NS %u: %llu MiB (%llu %u-byte "
                           "blocks + %u-byte metadata)",
@@ -460,12 +464,12 @@ nvme_bounce_xfer(struct nvme_namespace *ns, u64 lba, void *buf, u16 count,
     u16 blocks = count < max_blocks ? count : max_blocks;

if (write)
-        memcpy(ns->dma_buffer, buf, blocks * ns->block_size);
+        memcpy(nvme_dma_buffer, buf, blocks * ns->block_size);

-    int res = nvme_io_xfer(ns, lba, ns->dma_buffer, NULL, blocks, write);
+    int res = nvme_io_xfer(ns, lba, nvme_dma_buffer, NULL, blocks, write);

if (!write && res >= 0)
-        memcpy(buf, ns->dma_buffer, res * ns->block_size);
+        memcpy(buf, nvme_dma_buffer, res * ns->block_size);

return res;
 }
@@ -499,7 +503,7 @@ nvme_prpl_xfer(struct nvme_namespace *ns, u64 lba, void *buf, u16 count,
     if ((ns->block_size * count) > (NVME_PAGE_SIZE * 2)) {
         /* We need to describe more than 2 pages, build PRP List */
         u32 prpl_len = 0;
-        u64 *prpl = (void*)ns->dma_buffer;
+        u64 *prpl = nvme_dma_buffer;
         int first_page = 1;
         for (; size > 0; base += NVME_PAGE_SIZE, size -= NVME_PAGE_SIZE) {
             if (first_page) {

[Alexander Graf]

On 19.01.22 20:11, Kevin O'Connor wrote:
> There is no need to create multiple dma bounce buffers as the BIOS
> disk code isn't reentrant capable.
>
> Signed-off-by: Kevin O'Connor

Reviewed-by: Alexander Graf

Alex
> This is a minor cleanup on top of the previous nvme code series.
>
> -Kevin
>
> src/hw/nvme-int.h |  3 ---
>   src/hw/nvme.c     | 14 +++++++++-----
>   2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h
> index f0d717d..f9c807e 100644
> --- a/src/hw/nvme-int.h
> +++ b/src/hw/nvme-int.h
> @@ -117,9 +117,6 @@ struct nvme_namespace {
>       u32 block_size;
>       u32 metadata_size;
>       u32 max_req_size;
>
> /* Page aligned buffer of size NVME_PAGE_SIZE. */
>
> char *dma_buffer;
> };
>
> /* Data structures for NVMe admin identify commands */
>
> diff --git a/src/hw/nvme.c b/src/hw/nvme.c
> index 39b9138..0ba981c 100644
> --- a/src/hw/nvme.c
> +++ b/src/hw/nvme.c
> @@ -20,6 +20,9 @@
>   #include "nvme.h"
>   #include "nvme-int.h"
>
> +// Page aligned "dma bounce buffer" of size NVME_PAGE_SIZE in high memory
> +static void *nvme_dma_buffer;
> static void *
> zalloc_page_aligned(struct zone_s *zone, u32 size)
> {
>
> @@ -294,7 +297,8 @@ nvme_probe_ns(struct nvme_ctrl *ctrl, u32 ns_idx, u8 mdts)
>           ns->max_req_size = -1U;
>       }
> ns->dma_buffer = zalloc_page_aligned(&ZoneHigh, NVME_PAGE_SIZE);
>
> if (!nvme_dma_buffer)
>    nvme_dma_buffer = zalloc_page_aligned(&ZoneHigh, NVME_PAGE_SIZE);
>
> char *desc = znprintf(MAXDESCSIZE, "NVMe NS %u: %llu MiB (%llu %u-byte "
>                       "blocks + %u-byte metadata)",
>
> @@ -460,12 +464,12 @@ nvme_bounce_xfer(struct nvme_namespace *ns, u64 lba, void *buf, u16 count,
>       u16 blocks = count < max_blocks ? count : max_blocks;
>   if (write)
>    memcpy(ns->dma_buffer, buf, blocks * ns->block_size);
>    memcpy(nvme_dma_buffer, buf, blocks * ns->block_size);
>
> int res = nvme_io_xfer(ns, lba, ns->dma_buffer, NULL, blocks, write);
>
> int res = nvme_io_xfer(ns, lba, nvme_dma_buffer, NULL, blocks, write);
>
> if (!write && res >= 0)
>    memcpy(buf, ns->dma_buffer, res * ns->block_size);
>    memcpy(buf, nvme_dma_buffer, res * ns->block_size);
>
> return res;
>
> }
>
> @@ -499,7 +503,7 @@ nvme_prpl_xfer(struct nvme_namespace *ns, u64 lba, void *buf, u16 count,
>       if ((ns->block_size * count) > (NVME_PAGE_SIZE * 2)) {
>           /* We need to describe more than 2 pages, build PRP List */
>           u32 prpl_len = 0;
>    u64 *prpl = (void*)ns->dma_buffer;
>    u64 *prpl = nvme_dma_buffer;
>     int first_page = 1;
>     for (; size > 0; base += NVME_PAGE_SIZE, size -= NVME_PAGE_SIZE) {
>         if (first_page) {

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