[PATCH 4/6] Drivers: hv: vmbus: Introduce vmbus_request_addr_match()

Andrea Parri (Microsoft)
2022-04-07T04:32:47Z

The function can be used to retrieve and clear/remove a transation ID
from a channel requestor, provided the memory address corresponding to
the ID equals a specified address. The function, and its 'lockless'
variant __vmbus_request_addr_match(), will be used by hv_pci.

Refactor vmbus_request_addr() to reuse the 'newly' introduced code.

No functional change.

Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
---
drivers/hv/channel.c | 65 ++++++++++++++++++++++++++++++------------
include/linux/hyperv.h | 5 ++++
2 files changed, 52 insertions(+), 18 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 585a8084848bf..49f10a603a091 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -1279,17 +1279,11 @@ u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
}
EXPORT_SYMBOL_GPL(vmbus_next_request_id);

-/*
- * vmbus_request_addr - Returns the memory address stored at @trans_id
- * in @rqstor. Uses a spin lock to avoid race conditions.
- * @channel: Pointer to the VMbus channel struct
- * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
- * next request id.
- */
-u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
+/* As in vmbus_request_addr_match() but without the requestor lock */
+u64 __vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
+ u64 rqst_addr)
{
struct vmbus_requestor *rqstor = &channel->requestor;
- unsigned long flags;
u64 req_addr;

/* Check rqstor has been initialized */
@@ -1300,25 +1294,60 @@ u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
if (!trans_id)
return VMBUS_RQST_ERROR;

- spin_lock_irqsave(&rqstor->req_lock, flags);
-
/* Data corresponding to trans_id is stored at trans_id - 1 */
trans_id--;

/* Invalid trans_id */
- if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap)) {
- spin_unlock_irqrestore(&rqstor->req_lock, flags);
+ if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap))
return VMBUS_RQST_ERROR;
- }

req_addr = rqstor->req_arr[trans_id];
- rqstor->req_arr[trans_id] = rqstor->next_request_id;
- rqstor->next_request_id = trans_id;
+ if (rqst_addr == VMBUS_RQST_ADDR_ANY || req_addr == rqst_addr) {
+ rqstor->req_arr[trans_id] = rqstor->next_request_id;
+ rqstor->next_request_id = trans_id;

- /* The already held spin lock provides atomicity */
- bitmap_clear(rqstor->req_bitmap, trans_id, 1);
+ /* The already held spin lock provides atomicity */
+ bitmap_clear(rqstor->req_bitmap, trans_id, 1);
+ }
+
+ return req_addr;
+}
+EXPORT_SYMBOL_GPL(__vmbus_request_addr_match);
+
+/*
+ * vmbus_request_addr_match - Clears/removes @trans_id from the @channel's
+ * requestor, provided the memory address stored at @trans_id equals @rqst_addr
+ * (or provided @rqst_addr matches the sentinel value VMBUS_RQST_ADDR_ANY).
+ *
+ * Returns the memory address stored at @trans_id, or VMBUS_RQST_ERROR if
+ * @trans_id is not contained in the requestor.
+ *
+ * Acquires and releases the requestor spin lock.
+ */
+u64 vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
+ u64 rqst_addr)
+{
+ struct vmbus_requestor *rqstor = &channel->requestor;
+ unsigned long flags;
+ u64 req_addr;

+ spin_lock_irqsave(&rqstor->req_lock, flags);
+ req_addr = __vmbus_request_addr_match(channel, trans_id, rqst_addr);
spin_unlock_irqrestore(&rqstor->req_lock, flags);
+
return req_addr;
}
+EXPORT_SYMBOL_GPL(vmbus_request_addr_match);
+
+/*
+ * vmbus_request_addr - Returns the memory address stored at @trans_id
+ * in @rqstor. Uses a spin lock to avoid race conditions.
+ * @channel: Pointer to the VMbus channel struct
+ * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
+ * next request id.
+ */
+u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
+{
+ return vmbus_request_addr_match(channel, trans_id, VMBUS_RQST_ADDR_ANY);
+}
EXPORT_SYMBOL_GPL(vmbus_request_addr);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index a7cb596d893b1..c77d78f34b96a 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -788,6 +788,7 @@ struct vmbus_requestor {

#define VMBUS_NO_RQSTOR U64_MAX
#define VMBUS_RQST_ERROR (U64_MAX - 1)
+#define VMBUS_RQST_ADDR_ANY U64_MAX
/* NetVSC-specific */
#define VMBUS_RQST_ID_NO_RESPONSE (U64_MAX - 2)
/* StorVSC-specific */
@@ -1042,6 +1043,10 @@ struct vmbus_channel {
};

u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr);
+u64 __vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
+ u64 rqst_addr);
+u64 vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
+ u64 rqst_addr);
u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id);

static inline bool is_hvsock_channel(const struct vmbus_channel *c)
--
2.25.1