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[Qemu-devel] [PATCH 1/9] dma-helpers: Expose the sg mapping logic
From: |
Alex Pyrgiotis |
Subject: |
[Qemu-devel] [PATCH 1/9] dma-helpers: Expose the sg mapping logic |
Date: |
Wed, 16 Dec 2015 18:55:09 +0200 |
The mapping of scatter-gather lists from physical addresses (as
perceived by the guest kernel) to the virtual address space of the QEMU
process is a vital step for a DMA operation. This step is currently
implemented, amongst other things, in dma_blk_cb(), making it impossible
to be used by anyone else.
In order to pave the way for the DMA support of ioctl commands, expose
the aforementioned logic in a separate function called "dma_map_sg".
Also, expose some other important pieces too, such as the initialization
of the dbs structure.
Signed-off-by: Alex Pyrgiotis <address@hidden>
Signed-off-by: Dimitris Aragiorgis <address@hidden>
diff --git a/dma-helpers.c b/dma-helpers.c
index 4faec5d..c38661e 100644
--- a/dma-helpers.c
+++ b/dma-helpers.c
@@ -79,9 +79,10 @@ typedef struct {
QEMUIOVector iov;
QEMUBH *bh;
DMAIOFunc *io_func;
+ BlockCompletionFunc *dma_cb;
} DMAAIOCB;
-static void dma_blk_cb(void *opaque, int ret);
+static void dma_blk_io_cb(void *opaque, int ret);
static void reschedule_dma(void *opaque)
{
@@ -89,7 +90,7 @@ static void reschedule_dma(void *opaque)
qemu_bh_delete(dbs->bh);
dbs->bh = NULL;
- dma_blk_cb(dbs, 0);
+ dbs->dma_cb(dbs, 0);
}
static void dma_blk_unmap(DMAAIOCB *dbs)
@@ -120,21 +121,19 @@ static void dma_complete(DMAAIOCB *dbs, int ret)
qemu_aio_unref(dbs);
}
-static void dma_blk_cb(void *opaque, int ret)
+/*
+ * Create a QEMUIOVector from a scatter-gather list.
+ *
+ * This function does not copy the data of the scatter-gather list. Instead, it
+ * uses the dma_memory_map() function to map physical memory regions of the
+ * virtual device (as interpreted by the guest kernel) into the address space
+ * of the QEMU process, in order to have access to the data.
+ */
+static void dma_map_sg(DMAAIOCB *dbs)
{
- DMAAIOCB *dbs = (DMAAIOCB *)opaque;
dma_addr_t cur_addr, cur_len;
void *mem;
- trace_dma_blk_cb(dbs, ret);
-
- dbs->acb = NULL;
- dbs->sector_num += dbs->iov.size / 512;
-
- if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
- dma_complete(dbs, ret);
- return;
- }
dma_blk_unmap(dbs);
while (dbs->sg_cur_index < dbs->sg->nsg) {
@@ -162,9 +161,38 @@ static void dma_blk_cb(void *opaque, int ret)
if (dbs->iov.size & ~BDRV_SECTOR_MASK) {
qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & ~BDRV_SECTOR_MASK);
}
+}
+
+/*
+ * Callback function for DMA read/write operations.
+ *
+ * This function initiates the read/write operation and also acts as a
+ * completion callback. It uses the dma_map_sg() function to map the
+ * scatter-gather list to a QEMUIOVector and then passes this iovec to the
+ * underlying read/write I/O function.
+ *
+ * If the DMA operation cannot take place in one step, e.g. it couldn't map all
+ * the scatter-gather entries, then this function will do a partial I/O
+ * operation and once done, it will be called and will retry the I/O operation.
+ */
+static void dma_blk_io_cb(void *opaque, int ret)
+{
+ DMAAIOCB *dbs = (DMAAIOCB *)opaque;
+
+ trace_dma_blk_io_cb(dbs, ret);
+
+ dbs->acb = NULL;
+ dbs->sector_num += dbs->iov.size / 512;
+
+ if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
+ dma_complete(dbs, ret);
+ return;
+ }
+
+ dma_map_sg(dbs);
dbs->acb = dbs->io_func(dbs->blk, dbs->sector_num, &dbs->iov,
- dbs->iov.size / 512, dma_blk_cb, dbs);
+ dbs->iov.size / 512, dma_blk_io_cb, dbs);
assert(dbs->acb);
}
@@ -190,6 +218,22 @@ static const AIOCBInfo dma_aiocb_info = {
.cancel_async = dma_aio_cancel,
};
+/*
+ * Initialize the dbs structure and the QEMUIOVector to sane defaults.
+ */
+static void dma_init_dbs(DMAAIOCB *dbs, BlockBackend *blk, QEMUSGList *sg,
+ DMADirection dir)
+{
+ dbs->acb = NULL;
+ dbs->blk = blk;
+ dbs->sg = sg;
+ dbs->sg_cur_index = 0;
+ dbs->sg_cur_byte = 0;
+ dbs->dir = dir;
+ dbs->bh = NULL;
+ qemu_iovec_init(&dbs->iov, sg->nsg);
+}
+
BlockAIOCB *dma_blk_io(
BlockBackend *blk, QEMUSGList *sg, uint64_t sector_num,
DMAIOFunc *io_func, BlockCompletionFunc *cb,
@@ -199,21 +243,14 @@ BlockAIOCB *dma_blk_io(
trace_dma_blk_io(dbs, blk, sector_num, (dir == DMA_DIRECTION_TO_DEVICE));
- dbs->acb = NULL;
- dbs->blk = blk;
- dbs->sg = sg;
+ dma_init_dbs(dbs, blk, sg, dir);
dbs->sector_num = sector_num;
- dbs->sg_cur_index = 0;
- dbs->sg_cur_byte = 0;
- dbs->dir = dir;
dbs->io_func = io_func;
- dbs->bh = NULL;
- qemu_iovec_init(&dbs->iov, sg->nsg);
- dma_blk_cb(dbs, 0);
+ dbs->dma_cb = dma_blk_io_cb;
+ dbs->dma_cb(dbs, 0);
return &dbs->common;
}
-
BlockAIOCB *dma_blk_read(BlockBackend *blk,
QEMUSGList *sg, uint64_t sector,
void (*cb)(void *opaque, int ret), void *opaque)
diff --git a/trace-events b/trace-events
index 2fce98e..120cdd4 100644
--- a/trace-events
+++ b/trace-events
@@ -1127,7 +1127,7 @@ win_helper_retry(uint32_t tl) "tl=%d"
dma_blk_io(void *dbs, void *bs, int64_t sector_num, bool to_dev) "dbs=%p bs=%p
sector_num=%" PRId64 " to_dev=%d"
dma_aio_cancel(void *dbs) "dbs=%p"
dma_complete(void *dbs, int ret, void *cb) "dbs=%p ret=%d cb=%p"
-dma_blk_cb(void *dbs, int ret) "dbs=%p ret=%d"
+dma_blk_io_cb(void *dbs, int ret) "dbs=%p ret=%d"
dma_map_wait(void *dbs) "dbs=%p"
# ui/console.c
--
2.6.2
- Re: [Qemu-devel] [PATCH 0/9] Add full scatter-gather support for SCSI generic devices, (continued)
[Qemu-devel] [PATCH 5/9] scsi-generic: Separate `sg_io_hdr' initializations, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 4/9] scsi-generic: Add common functions, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 3/9] dma-helpers: Do not truncate small qiovs, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 7/9] scsi-generic: Make data-copying logic clearer, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 6/9] scsi-generic: Make request execution buf-specific, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 2/9] dma-helpers: Add support for ioctl operations, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 1/9] dma-helpers: Expose the sg mapping logic,
Alex Pyrgiotis <=
[Qemu-devel] [PATCH 8/9] scsi-generic: Factor out response interception, Alex Pyrgiotis, 2015/12/16
[Qemu-devel] [PATCH 9/9] scsi-generic: Allow full scatter-gather support, Alex Pyrgiotis, 2015/12/16