Fix kexec() flow in HyperV (#415)
When invoking kexec() on a Linux guest running on a Hyper-V host, the kernel panics. Created and applied kernel patch that fixes this issue.
This commit is contained in:
Christopher Co
GitHub
parent
cf46eb9bca
commit
c51c6d44f9
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@ -3,7 +3,7 @@
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Summary: Signed Linux Kernel for aarch64 systems
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Name: kernel-signed-aarch64
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Version: 5.4.72
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Release: 3%{?dist}
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Release: 4%{?dist}
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License: GPLv2
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Vendor: Microsoft Corporation
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Distribution: Mariner
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@ -80,6 +80,9 @@ ln -sf linux-%{uname_r}.cfg /boot/mariner.cfg
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%config %{_localstatedir}/lib/initramfs/kernel/%{uname_r}
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%changelog
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* Mon Nov 23 2020 Chris Co <chrco@microsoft.com> - 5.4.72-4
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- Update release number to match kernel spec
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* Mon Nov 16 2020 Suresh Babu Chalamalasetty <schalam@microsoft.com> - 5.4.72-3
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- Update release number
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@ -3,7 +3,7 @@
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Summary: Signed Linux Kernel for x86_64 systems
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Name: kernel-signed-x64
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Version: 5.4.72
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Release: 3%{?dist}
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Release: 4%{?dist}
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License: GPLv2
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Vendor: Microsoft Corporation
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Distribution: Mariner
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@ -80,6 +80,9 @@ ln -sf linux-%{uname_r}.cfg /boot/mariner.cfg
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%config %{_localstatedir}/lib/initramfs/kernel/%{uname_r}
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%changelog
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* Mon Nov 23 2020 Chris Co <chrco@microsoft.com> - 5.4.72-4
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- Update release number to match kernel spec
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* Mon Nov 16 2020 Suresh Babu Chalamalasetty <schalam@microsoft.com> - 5.4.72-3
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- Update release number
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@ -0,0 +1,64 @@
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From 4ffcffdc2e06186f35ffd41f46489d2027f32940 Mon Sep 17 00:00:00 2001
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From: Chris Co <chrco@microsoft.com>
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Date: Fri, 30 Oct 2020 05:20:29 +0000
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Subject: [PATCH] Drivers: hv: vmbus: Allow cleanup of VMBUS_CONNECT_CPU if
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disconnected
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When invoking kexec() on a Linux guest running on a Hyper-V host, the
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kernel panics.
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RIP: 0010:cpuhp_issue_call+0x137/0x140
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Call Trace:
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__cpuhp_remove_state_cpuslocked+0x99/0x100
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__cpuhp_remove_state+0x1c/0x30
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hv_kexec_handler+0x23/0x30 [hv_vmbus]
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hv_machine_shutdown+0x1e/0x30
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machine_shutdown+0x10/0x20
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kernel_kexec+0x6d/0x96
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__do_sys_reboot+0x1ef/0x230
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__x64_sys_reboot+0x1d/0x20
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do_syscall_64+0x6b/0x3d8
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entry_SYSCALL_64_after_hwframe+0x44/0xa9
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This was due to hv_synic_cleanup() callback returning -EBUSY to
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cpuhp_issue_call() when tearing down the VMBUS_CONNECT_CPU, even
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if the vmbus_connection.conn_state = DISCONNECTED. hv_synic_cleanup()
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should succeed in the case where vmbus_connection.conn_state
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is DISCONNECTED.
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Fix is to add an extra condition to test for
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vmbus_connection.conn_state == CONNECTED on the VMBUS_CONNECT_CPU and
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only return early if true. This way the kexec() path can still shut
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everything down while preserving the initial behavior of preventing
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CPU offlining on the VMBUS_CONNECT_CPU while the VM is running.
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Fixes: 8a857c55420f29 ("Drivers: hv: vmbus: Always handle the VMBus messages on CPU0")
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Signed-off-by: Chris Co <chrco@microsoft.com>
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Cc: stable@vger.kernel.org
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---
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drivers/hv/hv.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
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index 0cde10fe0e71..f202ac7f4b3d 100644
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--- a/drivers/hv/hv.c
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+++ b/drivers/hv/hv.c
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@@ -244,9 +244,13 @@ int hv_synic_cleanup(unsigned int cpu)
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/*
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* Hyper-V does not provide a way to change the connect CPU once
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- * it is set; we must prevent the connect CPU from going offline.
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+ * it is set; we must prevent the connect CPU from going offline
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+ * while the VM is running normally. But in the panic or kexec()
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+ * path where the vmbus is already disconnected, the CPU must be
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+ * allowed to shut down.
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*/
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- if (cpu == VMBUS_CONNECT_CPU)
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+ if (cpu == VMBUS_CONNECT_CPU &&
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+ vmbus_connection.conn_state == CONNECTED)
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return -EBUSY;
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/*
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--
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2.17.1
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@ -3,7 +3,7 @@
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Summary: Linux Kernel
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Name: kernel
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Version: 5.4.72
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Release: 3%{?dist}
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Release: 4%{?dist}
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License: GPLv2
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Vendor: Microsoft Corporation
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Distribution: Mariner
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@ -14,6 +14,7 @@ Source1: config
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Source2: config_aarch64
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# Arm64 HyperV support required patch
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Patch0: ver5_4_72_arm64_hyperv_support.patch
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Patch1: 0001-Drivers-hv-vmbus-Allow-cleanup-of-VMBUS_CONNECT_CPU-.patch
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# Kernel CVEs are addressed by moving to a newer version of the stable kernel.
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# Since kernel CVEs are filed against the upstream kernel version and not the
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# stable kernel version, our automated tooling will still flag the CVE as not
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@ -184,6 +185,8 @@ This package contains the 'perf' performance analysis tools for Linux kernel.
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%patch0 -p1
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%endif
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%patch1 -p1
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%build
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make mrproper
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@ -403,6 +406,9 @@ ln -sf linux-%{uname_r}.cfg /boot/mariner.cfg
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%{_libdir}/perf/include/bpf/*
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%changelog
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* Mon Nov 23 2020 Chris Co <chrco@microsoft.com> - 5.4.72-4
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- Apply patch to fix kexec in HyperV
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* Mon Nov 16 2020 Suresh Babu Chalamalasetty <schalam@microsoft.com> - 5.4.72-3
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- Disable kernel config SLUB_DEBUG_ON due to tcp throughput perf impact
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