Drivers: hv: vmbus: Introduce vmbus_request_addr_match()

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>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220419122325.10078-5-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 585a8084848bf7de236a06a09d98cd23efa92c8b..49f10a603a0914bf472030be03d930c088262e4f 100644 (file)
--- 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 7cb8718825eeb2a2973a8e859b370fa304826334..2e4962a2fbec41f574edfe08be07b8bee2c8b5f8 100644 (file)
--- 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)