Add a function to query for the preferred ring buffer size of VMBus
device. This will allow the drivers (eg. UIO) to allocate the most
optimized ring buffer size for devices.
Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Long Li <longli@xxxxxxxxxxxxx>
---
[V2]
- Added more details in commit message.
- Added comments for preferred ring sizes and there values.
- Added reviewed-by from Long Li.
drivers/hv/channel_mgmt.c | 15 ++++++++++++---
drivers/hv/hyperv_vmbus.h | 5 +++++
include/linux/hyperv.h | 2 ++
3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 2f4d09ce027a..3c6011a48dab 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -120,7 +120,9 @@ const struct vmbus_device vmbus_devs[] = {
},
/* File copy */
- { .dev_type = HV_FCOPY,
+ /* fcopy always uses 16KB ring buffer size and is working well for last many years */
+ { .pref_ring_size = 0x4000,
+ .dev_type = HV_FCOPY,
HV_FCOPY_GUID,
.perf_device = false,
.allowed_in_isolated = false,
@@ -140,12 +142,19 @@ const struct vmbus_device vmbus_devs[] = {
.allowed_in_isolated = false,
},
- /* Unknown GUID */
- { .dev_type = HV_UNKNOWN,
+ /*
+ * Unknown GUID
+ * 64 KB ring buffer + 4 KB header should be sufficient size for any Hyper-V device apart
+ * from HV_NIC and HV_SCSI. This case avoid the fallback for unknown devices to allocate
+ * much bigger (2 MB) of ring size.
+ */
+ { .pref_ring_size = 0x11000,
+ .dev_type = HV_UNKNOWN,
.perf_device = false,
.allowed_in_isolated = false,
},
};
+EXPORT_SYMBOL_GPL(vmbus_devs);
static const struct {
guid_t guid;
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index f6b1e710f805..76ac5185a01a 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -417,6 +417,11 @@ static inline bool hv_is_perf_channel(struct vmbus_channel *channel)
return vmbus_devs[channel->device_id].perf_device;
}
+static inline size_t hv_dev_ring_size(struct vmbus_channel *channel)
+{
+ return vmbus_devs[channel->device_id].pref_ring_size;
+}
+
static inline bool hv_is_allocated_cpu(unsigned int cpu)
{
struct vmbus_channel *channel, *sc;
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 6ef0557b4bff..7de9f90d3f95 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -820,6 +820,8 @@ struct vmbus_requestor {
#define VMBUS_RQST_RESET (U64_MAX - 3)
struct vmbus_device {
+ /* preferred ring buffer size in KB, 0 means no preferred size for this device */
+ size_t pref_ring_size;
u16 dev_type;
guid_t guid;
bool perf_device;
--
2.34.1
