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[51.6.142.41]) by smtp.gmail.com with ESMTPSA id g2sm5779960wrs.42.2020.03.17.10.35.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Mar 2020 10:35:56 -0700 (PDT) Date: Tue, 17 Mar 2020 17:35:53 +0000 From: Wei Liu To: ltykernel@gmail.com Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, liuwe@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, michael.h.kelley@microsoft.com, Tianyu Lan , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, vkuznets@redhat.com, Wei Liu Subject: Re: [PATCH 0/4] x86/Hyper-V: Unload vmbus channel in hv panic callback Message-ID: <20200317173553.jerf6gjtaotqjbac@debian> References: <20200317132523.1508-1-Tianyu.Lan@microsoft.com> <20200317132523.1508-2-Tianyu.Lan@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200317132523.1508-2-Tianyu.Lan@microsoft.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 17, 2020 at 06:25:20AM -0700, ltykernel@gmail.com wrote: > From: Tianyu Lan > > Customer reported Hyper-V VM still responded network traffic > ack packets after kernel panic with kernel parameter "panic=0”. > This becauses vmbus driver interrupt handler still works > on the panic cpu after kernel panic. Panic cpu falls into > infinite loop of panic() with interrupt enabled at that point. > Vmbus driver can still handle network traffic. > > This confuses remote service that the panic system is still > alive when it gets ack packets. Unload vmbus channel in hv panic > callback and fix it. > > vmbus_initiate_unload() maybe double called during panic process > (e.g, hyperv_panic_event() and hv_crash_handler()). So check > and set connection state in vmbus_initiate_unload() to resolve > reenter issue. > > Signed-off-by: Tianyu Lan > --- > drivers/hv/channel_mgmt.c | 5 +++++ > drivers/hv/vmbus_drv.c | 17 +++++++++-------- > 2 files changed, 14 insertions(+), 8 deletions(-) > > diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c > index 0370364169c4..893493f2b420 100644 > --- a/drivers/hv/channel_mgmt.c > +++ b/drivers/hv/channel_mgmt.c > @@ -839,6 +839,9 @@ void vmbus_initiate_unload(bool crash) > { > struct vmbus_channel_message_header hdr; > > + if (vmbus_connection.conn_state == DISCONNECTED) > + return; > + > /* Pre-Win2012R2 hosts don't support reconnect */ > if (vmbus_proto_version < VERSION_WIN8_1) > return; > @@ -857,6 +860,8 @@ void vmbus_initiate_unload(bool crash) > wait_for_completion(&vmbus_connection.unload_event); > else > vmbus_wait_for_unload(); > + > + vmbus_connection.conn_state = DISCONNECTED; This is only set at the end of the function. I don't see how this solve the re-entrant issue with the check at the beginning. Do I miss anything here? Maybe this function should check and set the state to DISCONNECTING/DISCONNECTED at the beginning of this function? Wei.