3.2.65-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: "K. Y. Srinivasan" <k...@microsoft.com>
commit b29ef3546aecb253a5552b198cef23750d56e1e4 upstream.
Minimize failures in this function by pre-allocating the buffer
for posting messages. The hypercall for posting the message can fail
for a number of reasons:
1. Transient resource related issues
2. Buffer alignment
3. Buffer cannot span a page boundry
We address issues 2 and 3 by preallocating a per-cpu page for the buffer.
Transient resource related failures are handled by retrying by the callers
of this function.
This patch is based on the investigation
done by Dexuan Cui <de...@microsoft.com>.
I would like to thank Sitsofe Wheeler <sits...@yahoo.com>
for reporting the issue and helping in debuggging.
Signed-off-by: K. Y. Srinivasan <k...@microsoft.com>
Reported-by: Sitsofe Wheeler <sits...@yahoo.com>
Tested-by: Sitsofe Wheeler <sits...@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
[bwh: Backported to 3.2:
- s/NR_CPUS/MAX_NUM_CPUS/
- Adjust context, indentation
- Also free the page in hv_synic_init() error path]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
drivers/hv/hv.c | 27 +++++++++++++++------------
drivers/hv/hyperv_vmbus.h | 4 ++++
2 files changed, 19 insertions(+), 12 deletions(-)
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -158,6 +158,8 @@ int hv_init(void)
memset(hv_context.synic_event_page, 0, sizeof(void *) * MAX_NUM_CPUS);
memset(hv_context.synic_message_page, 0,
sizeof(void *) * MAX_NUM_CPUS);
+ memset(hv_context.post_msg_page, 0,
+ sizeof(void *) * MAX_NUM_CPUS);
if (!query_hypervisor_presence())
goto cleanup;
@@ -258,26 +260,18 @@ u16 hv_post_message(union hv_connection_
enum hv_message_type message_type,
void *payload, size_t payload_size)
{
- struct aligned_input {
- u64 alignment8;
- struct hv_input_post_message msg;
- };
struct hv_input_post_message *aligned_msg;
u16 status;
- unsigned long addr;
if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
return -EMSGSIZE;
- addr = (unsigned long)kmalloc(sizeof(struct aligned_input), GFP_ATOMIC);
- if (!addr)
- return -ENOMEM;
-
aligned_msg = (struct hv_input_post_message *)
- (ALIGN(addr, HV_HYPERCALL_PARAM_ALIGN));
+ hv_context.post_msg_page[get_cpu()];
aligned_msg->connectionid = connection_id;
+ aligned_msg->reserved = 0;
aligned_msg->message_type = message_type;
aligned_msg->payload_size = payload_size;
memcpy((void *)aligned_msg->payload, payload, payload_size);
@@ -285,8 +279,7 @@ u16 hv_post_message(union hv_connection_
status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
& 0xFFFF;
- kfree((void *)addr);
-
+ put_cpu();
return status;
}
@@ -347,6 +340,14 @@ void hv_synic_init(void *irqarg)
goto cleanup;
}
+ hv_context.post_msg_page[cpu] =
+ (void *)get_zeroed_page(GFP_ATOMIC);
+
+ if (hv_context.post_msg_page[cpu] == NULL) {
+ pr_err("Unable to allocate post msg page\n");
+ goto cleanup;
+ }
+
/* Setup the Synic's message page */
rdmsrl(HV_X64_MSR_SIMP, simp.as_uint64);
simp.simp_enabled = 1;
@@ -388,6 +389,8 @@ cleanup:
if (hv_context.synic_message_page[cpu])
free_page((unsigned long)hv_context.synic_message_page[cpu]);
+ if (hv_context.post_msg_page[cpu])
+ free_page((unsigned long)hv_context.post_msg_page[cpu]);
return;
}
@@ -426,4 +429,5 @@ void hv_synic_cleanup(void *arg)
free_page((unsigned long)hv_context.synic_message_page[cpu]);
free_page((unsigned long)hv_context.synic_event_page[cpu]);
+ free_page((unsigned long)hv_context.post_msg_page[cpu]);
}
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -485,6 +485,10 @@ struct hv_context {
void *synic_message_page[MAX_NUM_CPUS];
void *synic_event_page[MAX_NUM_CPUS];
+ /*
+ * buffer to post messages to the host.
+ */
+ void *post_msg_page[MAX_NUM_CPUS];
};
extern struct hv_context hv_context;
--
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