[Devel] [PATCH VZ9] x86/hyperv: fix kexec crash due to VP assist page corruption
Pavel Tikhomirov
ptikhomirov at virtuozzo.com
Thu Jan 23 09:21:39 MSK 2025
From: "Anirudh Rayabharam (Microsoft)" <anirudh at anirudhrb.com>
commit 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when
CPUs go online/offline") introduces a new cpuhp state for hyperv
initialization.
cpuhp_setup_state() returns the state number if state is
CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN and 0 for all other states.
For the hyperv case, since a new cpuhp state was introduced it would
return 0. However, in hv_machine_shutdown(), the cpuhp_remove_state() call
is conditioned upon "hyperv_init_cpuhp > 0". This will never be true and
so hv_cpu_die() won't be called on all CPUs. This means the VP assist page
won't be reset. When the kexec kernel tries to setup the VP assist page
again, the hypervisor corrupts the memory region of the old VP assist page
causing a panic in case the kexec kernel is using that memory elsewhere.
This was originally fixed in commit dfe94d4086e4 ("x86/hyperv: Fix kexec
panic/hang issues").
Get rid of hyperv_init_cpuhp entirely since we are no longer using a
dynamic cpuhp state and use CPUHP_AP_HYPERV_ONLINE directly with
cpuhp_remove_state().
Cc: stable at vger.kernel.org
Fixes: 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when CPUs go online/offline")
Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh at anirudhrb.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets at redhat.com>
Reviewed-by: Michael Kelley <mhklinux at outlook.com>
Link: https://lore.kernel.org/r/20240828112158.3538342-1-anirudh@anirudhrb.com
Signed-off-by: Wei Liu <wei.liu at kernel.org>
Message-ID: <20240828112158.3538342-1-anirudh at anirudhrb.com>
Note: This patch resets VP assist page before kexec on old kernel, this
means that kexec from the unfixed kernel to the fixed kernel will still
be crashing.
https://virtuozzo.atlassian.net/browse/VSTOR-97950
(cherry picked from commit b9af6418279c4cf73ca073f8ea024992b38be8ab)
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
arch/x86/hyperv/hv_init.c | 5 +----
arch/x86/include/asm/mshyperv.h | 1 -
arch/x86/kernel/cpu/mshyperv.c | 4 ++--
3 files changed, 3 insertions(+), 7 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index ee199f802bfa4..ecdfa0c485ee6 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -35,7 +35,6 @@
#include <clocksource/hyperv_timer.h>
#include <linux/highmem.h>
-int hyperv_init_cpuhp;
u64 hv_current_partition_id = ~0ull;
EXPORT_SYMBOL_GPL(hv_current_partition_id);
@@ -647,8 +646,6 @@ void __init hyperv_init(void)
register_syscore_ops(&hv_syscore_ops);
- hyperv_init_cpuhp = cpuhp;
-
if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID)
hv_get_partition_id();
@@ -677,7 +674,7 @@ void __init hyperv_init(void)
clean_guest_os_id:
wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);
- cpuhp_remove_state(cpuhp);
+ cpuhp_remove_state(CPUHP_AP_HYPERV_ONLINE);
free_ghcb_page:
free_percpu(hv_ghcb_pg);
free_vp_assist_page:
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 896445edc6a8e..ec95d6e9f1682 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -40,7 +40,6 @@ static inline unsigned char hv_get_nmi_reason(void)
}
#if IS_ENABLED(CONFIG_HYPERV)
-extern int hyperv_init_cpuhp;
extern bool hyperv_paravisor_present;
extern void *hv_hypercall_pg;
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 2c889b0d2a08b..abc8a7ab5c4e9 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -199,8 +199,8 @@ static void hv_machine_shutdown(void)
* Call hv_cpu_die() on all the CPUs, otherwise later the hypervisor
* corrupts the old VP Assist Pages and can crash the kexec kernel.
*/
- if (kexec_in_progress && hyperv_init_cpuhp > 0)
- cpuhp_remove_state(hyperv_init_cpuhp);
+ if (kexec_in_progress)
+ cpuhp_remove_state(CPUHP_AP_HYPERV_ONLINE);
/* The function calls stop_other_cpus(). */
native_machine_shutdown();
--
2.47.1
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