From: Chris Co <chrco@linux.microsoft.com>
To: linux-hyperv@vger.kernel.org
Cc: kys@microsoft.com, haiyangz@microsoft.com,
sthemmin@microsoft.com, wei.liu@kernel.org, chrco@microsoft.com,
mikelley@microsoft.com, andrea.parri@microsoft.com,
parri.andrea@gmail.com, linux-kernel@vger.kernel.org
Subject: [PATCH] Drivers: hv: vmbus: Allow cleanup of VMBUS_CONNECT_CPU if disconnected
Date: Tue, 10 Nov 2020 19:01:18 +0000 [thread overview]
Message-ID: <20201110190118.15596-1-chrco@linux.microsoft.com> (raw)
From: Chris Co <chrco@microsoft.com>
When invoking kexec() on a Linux guest running on a Hyper-V host, the
kernel panics.
RIP: 0010:cpuhp_issue_call+0x137/0x140
Call Trace:
__cpuhp_remove_state_cpuslocked+0x99/0x100
__cpuhp_remove_state+0x1c/0x30
hv_kexec_handler+0x23/0x30 [hv_vmbus]
hv_machine_shutdown+0x1e/0x30
machine_shutdown+0x10/0x20
kernel_kexec+0x6d/0x96
__do_sys_reboot+0x1ef/0x230
__x64_sys_reboot+0x1d/0x20
do_syscall_64+0x6b/0x3d8
entry_SYSCALL_64_after_hwframe+0x44/0xa9
This was due to hv_synic_cleanup() callback returning -EBUSY to
cpuhp_issue_call() when tearing down the VMBUS_CONNECT_CPU, even
if the vmbus_connection.conn_state = DISCONNECTED. hv_synic_cleanup()
should succeed in the case where vmbus_connection.conn_state
is DISCONNECTED.
Fix is to add an extra condition to test for
vmbus_connection.conn_state == CONNECTED on the VMBUS_CONNECT_CPU and
only return early if true. This way the kexec() path can still shut
everything down while preserving the initial behavior of preventing
CPU offlining on the VMBUS_CONNECT_CPU while the VM is running.
Fixes: 8a857c55420f29 ("Drivers: hv: vmbus: Always handle the VMBus messages on CPU0")
Signed-off-by: Chris Co <chrco@microsoft.com>
Cc: stable@vger.kernel.org
---
drivers/hv/hv.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 0cde10fe0e71..f202ac7f4b3d 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -244,9 +244,13 @@ int hv_synic_cleanup(unsigned int cpu)
/*
* Hyper-V does not provide a way to change the connect CPU once
- * it is set; we must prevent the connect CPU from going offline.
+ * it is set; we must prevent the connect CPU from going offline
+ * while the VM is running normally. But in the panic or kexec()
+ * path where the vmbus is already disconnected, the CPU must be
+ * allowed to shut down.
*/
- if (cpu == VMBUS_CONNECT_CPU)
+ if (cpu == VMBUS_CONNECT_CPU &&
+ vmbus_connection.conn_state == CONNECTED)
return -EBUSY;
/*
--
2.17.1
next reply other threads:[~2020-11-10 19:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 19:01 Chris Co [this message]
2020-11-10 20:18 ` [PATCH] Drivers: hv: vmbus: Allow cleanup of VMBUS_CONNECT_CPU if disconnected Andrea Parri
2020-11-11 10:59 ` Wei Liu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201110190118.15596-1-chrco@linux.microsoft.com \
--to=chrco@linux.microsoft.com \
--cc=andrea.parri@microsoft.com \
--cc=chrco@microsoft.com \
--cc=haiyangz@microsoft.com \
--cc=kys@microsoft.com \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mikelley@microsoft.com \
--cc=parri.andrea@gmail.com \
--cc=sthemmin@microsoft.com \
--cc=wei.liu@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.