This is a note to let you know that I've just added the patch titled
Drivers: hv: vmbus: Fix vmbus_wait_for_unload() to scan present CPUs
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drivers-hv-vmbus-fix-vmbus_wait_for_unload-to-scan-present-cpus.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 320805ab61e5f1e2a5729ae266e16bec2904050c Mon Sep 17 00:00:00 2001
From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Date: Thu, 18 May 2023 08:13:52 -0700
Subject: Drivers: hv: vmbus: Fix vmbus_wait_for_unload() to scan present CPUs
From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
commit 320805ab61e5f1e2a5729ae266e16bec2904050c upstream.
vmbus_wait_for_unload() may be called in the panic path after other
CPUs are stopped. vmbus_wait_for_unload() currently loops through
online CPUs looking for the UNLOAD response message. But the values of
CONFIG_KEXEC_CORE and crash_kexec_post_notifiers affect the path used
to stop the other CPUs, and in one of the paths the stopped CPUs
are removed from cpu_online_mask. This removal happens in both
x86/x64 and arm64 architectures. In such a case, vmbus_wait_for_unload()
only checks the panic'ing CPU, and misses the UNLOAD response message
except when the panic'ing CPU is CPU 0. vmbus_wait_for_unload()
eventually times out, but only after waiting 100 seconds.
Fix this by looping through *present* CPUs in vmbus_wait_for_unload().
The cpu_present_mask is not modified by stopping the other CPUs in the
panic path, nor should it be.
Also, in a CoCo VM the synic_message_page is not allocated in
hv_synic_alloc(), but is set and cleared in hv_synic_enable_regs()
and hv_synic_disable_regs() such that it is set only when the CPU is
online. If not all present CPUs are online when vmbus_wait_for_unload()
is called, the synic_message_page might be NULL. Add a check for this.
Fixes: cd95aad55793 ("Drivers: hv: vmbus: handle various crash scenarios")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: John Starks <jostarks@xxxxxxxxxxxxx>
Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Link: https://lore.kernel.org/r/1684422832-38476-1-git-send-email-mikelley@xxxxxxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/hv/channel_mgmt.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -813,11 +813,22 @@ static void vmbus_wait_for_unload(void)
if (completion_done(&vmbus_connection.unload_event))
goto completed;
- for_each_online_cpu(cpu) {
+ for_each_present_cpu(cpu) {
struct hv_per_cpu_context *hv_cpu
= per_cpu_ptr(hv_context.cpu_context, cpu);
+ /*
+ * In a CoCo VM the synic_message_page is not allocated
+ * in hv_synic_alloc(). Instead it is set/cleared in
+ * hv_synic_enable_regs() and hv_synic_disable_regs()
+ * such that it is set only when the CPU is online. If
+ * not all present CPUs are online, the message page
+ * might be NULL, so skip such CPUs.
+ */
page_addr = hv_cpu->synic_message_page;
+ if (!page_addr)
+ continue;
+
msg = (struct hv_message *)page_addr
+ VMBUS_MESSAGE_SINT;
@@ -851,11 +862,14 @@ completed:
* maybe-pending messages on all CPUs to be able to receive new
* messages after we reconnect.
*/
- for_each_online_cpu(cpu) {
+ for_each_present_cpu(cpu) {
struct hv_per_cpu_context *hv_cpu
= per_cpu_ptr(hv_context.cpu_context, cpu);
page_addr = hv_cpu->synic_message_page;
+ if (!page_addr)
+ continue;
+
msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
msg->header.message_type = HVMSG_NONE;
}
Patches currently in stable-queue which might be from mikelley@xxxxxxxxxxxxx are
queue-4.19/drivers-hv-vmbus-fix-vmbus_wait_for_unload-to-scan-present-cpus.patch
queue-4.19/pci-hv-fix-a-race-condition-bug-in-hv_pci_query_relations.patch
