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Re: [Qemu-devel] [Qemu-block] [PATCH] nvme: add Get/Set Feature Timestam

From: Heitke, Kenneth
Subject: Re: [Qemu-devel] [Qemu-block] [PATCH] nvme: add Get/Set Feature Timestamp support
Date: Fri, 17 May 2019 19:49:18 -0600
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

On 5/17/2019 12:24 AM, Klaus Birkelund wrote:
On Fri, May 17, 2019 at 07:35:04AM +0200, Klaus Birkelund wrote:
Hi Kenneth,

On Thu, May 16, 2019 at 05:24:47PM -0600, Heitke, Kenneth wrote:
Hi Klaus, thank you for you review. I have one comment inline

On 5/14/2019 12:02 AM, Klaus Birkelund wrote:
On Fri, Apr 05, 2019 at 03:41:17PM -0600, Kenneth Heitke wrote:
Signed-off-by: Kenneth Heitke <address@hidden>
   hw/block/nvme.c       | 120 +++++++++++++++++++++++++++++++++++++++++-
   hw/block/nvme.h       |   3 ++
   hw/block/trace-events |   2 +
   include/block/nvme.h  |   2 +
   4 files changed, 125 insertions(+), 2 deletions(-)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 7caf92532a..e775e89299 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -219,6 +219,30 @@ static uint16_t nvme_map_prp(QEMUSGList *qsg, QEMUIOVector 
*iov, uint64_t prp1,
+static uint16_t nvme_dma_write_prp(NvmeCtrl *n, uint8_t *ptr, uint32_t len,
+                                   uint64_t prp1, uint64_t prp2)
+    QEMUSGList qsg;
+    QEMUIOVector iov;
+    uint16_t status = NVME_SUCCESS;
+    if (nvme_map_prp(&qsg, &iov, prp1, prp2, len, n)) {
+        return NVME_INVALID_FIELD | NVME_DNR;
+    }
+    if (qsg.nsg > 0) {
+        if (dma_buf_write(ptr, len, &qsg)) {
+            status = NVME_INVALID_FIELD | NVME_DNR;
+        }
+        qemu_sglist_destroy(&qsg);
+    } else {
+        if (qemu_iovec_from_buf(&iov, 0, ptr, len) != len) {

This should be `qemu_iovec_to_buf`.

This function is transferring data from the "host" to the device so I
believe I am using the correct function.

Exactly, but this means that you need to populate `ptr` with data
described by the prps, hence dma_buf_*write* and qemu_iovec_*to*_buf. In
this case `ptr` is set to the address of the uint64_t timestamp, and
that is what we need to write to.

I was going to argue with the fact that nvme_dma_read_prp uses
qemu_iovec_from_buf. But it uses _to_buf which as far as I can tell is
also wrong.

Okay, I'm onboard. You're correct. I'll update my patch and re-submit. I can also submit a patch to fix nvme_dma_read_prp() unless you or someone else wants to.


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