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Subject[PATCH 2/4] Drivers: hv: ring_buffer: wrap around mappings for ring buffers
Date
From: Vitaly Kuznetsov <vkuznets@redhat.com>

Make it possible to always use a single memcpy() or to provide a direct
link to a packet on the ring buffer by creating virtual mapping for two
copies of the ring buffer with vmap(). Utilize currently empty
hv_ringbuffer_cleanup() to do the unmap.

While on it, replace sizeof(struct hv_ring_buffer) check
in hv_ringbuffer_init() with BUILD_BUG_ON() as it is a compile time check.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Tested-by: Dexuan Cui <decui@microsoft.com>
---
drivers/hv/channel.c | 29 ++++++++++++++---------------
drivers/hv/hyperv_vmbus.h | 4 ++--
drivers/hv/ring_buffer.c | 39 +++++++++++++++++++++++++++++++++------
3 files changed, 49 insertions(+), 23 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 901b6ce..aad26da 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -75,7 +75,6 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
{
struct vmbus_channel_open_channel *open_msg;
struct vmbus_channel_msginfo *open_info = NULL;
- void *in, *out;
unsigned long flags;
int ret, err = 0;
unsigned long t;
@@ -113,23 +112,21 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
goto error_set_chnstate;
}

- out = page_address(page);
- in = (void *)((unsigned long)out + send_ringbuffer_size);
-
- newchannel->ringbuffer_pages = out;
+ newchannel->ringbuffer_pages = page_address(page);
newchannel->ringbuffer_pagecount = (send_ringbuffer_size +
recv_ringbuffer_size) >> PAGE_SHIFT;

- ret = hv_ringbuffer_init(
- &newchannel->outbound, out, send_ringbuffer_size);
+ ret = hv_ringbuffer_init(&newchannel->outbound, page,
+ send_ringbuffer_size >> PAGE_SHIFT);

if (ret != 0) {
err = ret;
goto error_free_pages;
}

- ret = hv_ringbuffer_init(
- &newchannel->inbound, in, recv_ringbuffer_size);
+ ret = hv_ringbuffer_init(&newchannel->inbound,
+ &page[send_ringbuffer_size >> PAGE_SHIFT],
+ recv_ringbuffer_size >> PAGE_SHIFT);
if (ret != 0) {
err = ret;
goto error_free_pages;
@@ -140,10 +137,10 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
newchannel->ringbuffer_gpadlhandle = 0;

ret = vmbus_establish_gpadl(newchannel,
- newchannel->outbound.ring_buffer,
- send_ringbuffer_size +
- recv_ringbuffer_size,
- &newchannel->ringbuffer_gpadlhandle);
+ page_address(page),
+ send_ringbuffer_size +
+ recv_ringbuffer_size,
+ &newchannel->ringbuffer_gpadlhandle);

if (ret != 0) {
err = ret;
@@ -219,8 +216,10 @@ error_free_gpadl:
vmbus_teardown_gpadl(newchannel, newchannel->ringbuffer_gpadlhandle);
kfree(open_info);
error_free_pages:
- free_pages((unsigned long)out,
- get_order(send_ringbuffer_size + recv_ringbuffer_size));
+ hv_ringbuffer_cleanup(&newchannel->outbound);
+ hv_ringbuffer_cleanup(&newchannel->inbound);
+ __free_pages(page,
+ get_order(send_ringbuffer_size + recv_ringbuffer_size));
error_set_chnstate:
newchannel->state = CHANNEL_OPEN_STATE;
return err;
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index ddcc348..a5b4442 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -522,8 +522,8 @@ extern unsigned int host_info_edx;
/* Interface */


-int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, void *buffer,
- u32 buflen);
+int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
+ struct page *pages, u32 pagecnt);

void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index e3edcae..7e21c2c 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -27,6 +27,8 @@
#include <linux/mm.h>
#include <linux/hyperv.h>
#include <linux/uio.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>

#include "hyperv_vmbus.h"

@@ -243,22 +245,46 @@ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,

/* Initialize the ring buffer. */
int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
- void *buffer, u32 buflen)
+ struct page *pages, u32 page_cnt)
{
- if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
- return -EINVAL;
+ int i;
+ struct page **pages_wraparound;
+
+ BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));

memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));

- ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
+ /*
+ * First page holds struct hv_ring_buffer, do wraparound mapping for
+ * the rest.
+ */
+ pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),
+ GFP_KERNEL);
+ if (!pages_wraparound)
+ return -ENOMEM;
+
+ pages_wraparound[0] = pages;
+ for (i = 0; i < 2 * (page_cnt - 1); i++)
+ pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
+
+ ring_info->ring_buffer = (struct hv_ring_buffer *)
+ vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
+
+ kfree(pages_wraparound);
+
+
+ if (!ring_info->ring_buffer)
+ return -ENOMEM;
+
ring_info->ring_buffer->read_index =
ring_info->ring_buffer->write_index = 0;

/* Set the feature bit for enabling flow control. */
ring_info->ring_buffer->feature_bits.value = 1;

- ring_info->ring_size = buflen;
- ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
+ ring_info->ring_size = page_cnt << PAGE_SHIFT;
+ ring_info->ring_datasize = ring_info->ring_size -
+ sizeof(struct hv_ring_buffer);

spin_lock_init(&ring_info->ring_lock);

@@ -268,6 +294,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
/* Cleanup the ring buffer. */
void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
{
+ vunmap(ring_info->ring_buffer);
}

/* Write to the ring buffer. */
--
1.7.4.1
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