x86: vmclear vmcss on all cpus when doing kdump if necessary
Subsystems (5)
v9 cover x86: vmclear vmcss on all cpus when doing kdump if necessary
Currently, kdump just makes all the logical processors leave VMX operation by executing VMXOFF instruction, so any VMCSs active on the logical processors may be corrupted. But, sometimes, we need the VMCSs to debug guest images contained in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before executing the VMXOFF instruction.
The patch set provides a way to VMCLEAR vmcss related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
Changelog from v8 to v9:
1. KEXEC: use a callback function instead of a notifier.
2. KVM-INTEL: use a new vmclear function instead of just calling vmclear_local_loaded_vmcss to make sure we just do the core vmclear operation in kdump.
Changelog from v7 to v8:
1. KEXEC: regression for using name crash_notifier_list and remove comments related to KVM
and just call function atomic_notifier_call_chain directly.
Changelog from v6 to v7:
1. KVM-INTEL: in hardware_disable, we needn't disable the vmclear, so remove it.
Changelog from v5 to v6:
1. KEXEC: the atomic notifier list renamed:
crash_notifier_list --> vmclear_notifier_list
2. KVM-INTEL: provide empty functions if CONFIG_KEXEC is not defined and remove unnecessary #ifdef's.
Changelog from v4 to v5:
1. use an atomic notifier instead of function call, so have all the vmclear codes in vmx.c.
Changelog from v3 to v4:
1. add a new percpu variable vmclear_skipped to skip vmclear in kdump in some conditions.
Changelog from v2 to v3:
1. remove unnecessary conditions in function cpu_emergency_clear_loaded_vmcss as Marcelo suggested.
Changelog from v1 to v2:
1. remove the sysctl and clear VMCSs unconditionally.
Zhang Yanfei (2):
x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
KVM-INTEL: provide the vmclear function and a bitmap to support
VMCLEAR in kdump
arch/x86/include/asm/kexec.h | 2 + arch/x86/kernel/crash.c | 25 ++++++++++++++++ arch/x86/kvm/vmx.c | 65 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 92 insertions(+), 0 deletions(-)
PATCH v9 1/2 x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
This patch provides a way to VMCLEAR VMCSs related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
--- arch/x86/include/asm/kexec.h | 2 ++ arch/x86/kernel/crash.c | 25 +++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 0 deletions(-)
arch/x86/include/asm/kexec.h +2 -0
@@ -163,6 +163,8 @@ struct kimage_arch { };#endif +extern void (*crash_vmclear_loaded_vmcss)(void ); +#endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_KEXEC_H */
arch/x86/kernel/crash.c +25 -0
@@ -16,6 +16,7 @@#include <linux/delay.h> #include <linux/elf.h> #include <linux/elfcore.h> +#include <linux/module.h> #include <asm/processor.h> #include <asm/hardirq.h>
@@ -29,6 +30,20 @@#include <asm/virtext.h> int in_crash_kexec; + +/* +* This is used to VMCLEAR all VMCSs loaded on the +* processor. And when loading kvm_intel module, the +* callback function pointer will be assigned. +*/ +void (*crash_vmclear_loaded_vmcss)(void ) =NULL ; +EXPORT_SYMBOL_GPL (crash_vmclear_loaded_vmcss); + +static inline void cpu_emergency_vmclear_loaded_vmcss (void ) +{ +if (crash_vmclear_loaded_vmcss) +crash_vmclear_loaded_vmcss (); +}#if defined(CONFIG_SMP ) && defined(CONFIG_X86_LOCAL_APIC )
@@ -46,6 +61,11 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)#endif crash_save_cpu (regs, cpu); +/* +* VMCLEAR VMCSs loaded on all cpus if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Disable VMX or SVM if needed. * * We need to disable virtualization on all CPUs.
@@ -88,6 +108,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)kdump_nmi_shootdown_cpus (); +/* +* VMCLEAR VMCSs loaded on this cpu if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Booting kdump kernel with VMX or SVM enabled won't work, * because (among other limitations) we can't disable paging * with the virt flags.
Signature · 1 line
1.7.1
Re: [PATCH v9 1/2] x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
Eric, can you ACK it?
Quoted 83 lines · Zhang Yanfei
This patch provides a way to VMCLEAR VMCSs related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
Signed-off-by Zhang Yanfei <[email protected]>--- arch/x86/include/asm/kexec.h | 2 ++ arch/x86/kernel/crash.c | 25 +++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 0 deletions(-)arch/x86/include/asm/kexec.h +2
-0@@ -163,6 +163,8 @@ struct kimage_arch { };#endif +extern void (*crash_vmclear_loaded_vmcss)(void ); +#endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_KEXEC_H */ arch/x86/kernel/crash.c +25
-0@@ -16,6 +16,7 @@#include <linux/delay.h> #include <linux/elf.h> #include <linux/elfcore.h> +#include <linux/module.h> #include <asm/processor.h> #include <asm/hardirq.h> @@ -29,6 +30,20 @@#include <asm/virtext.h> int in_crash_kexec; + +/* +* This is used to VMCLEAR all VMCSs loaded on the +* processor. And when loading kvm_intel module, the +* callback function pointer will be assigned. +*/ +void (*crash_vmclear_loaded_vmcss)(void ) =NULL ; +EXPORT_SYMBOL_GPL (crash_vmclear_loaded_vmcss); + +static inline void cpu_emergency_vmclear_loaded_vmcss (void ) +{ +if (crash_vmclear_loaded_vmcss) +crash_vmclear_loaded_vmcss (); +}#if defined(CONFIG_SMP ) && defined(CONFIG_X86_LOCAL_APIC )@@ -46,6 +61,11 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)#endif crash_save_cpu (regs, cpu); +/* +* VMCLEAR VMCSs loaded on all cpus if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Disable VMX or SVM if needed. * * We need to disable virtualization on all CPUs. @@ -88,6 +108,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)kdump_nmi_shootdown_cpus (); +/* +* VMCLEAR VMCSs loaded on this cpu if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Booting kdump kernel with VMX or SVM enabled won't work, * because (among other limitations) we can't disable paging * with the virt flags. Signature · 1 line
1.7.1
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Gleb.
Re: [PATCH v9 1/2] x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
Quoted 2 lines · Gleb Natapov
Eric, can you ACK it?
Eric, ping.
Quoted 83 lines · Zhang Yanfei
Quoted 82 lines
This patch provides a way to VMCLEAR VMCSs related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
Signed-off-by Zhang Yanfei <[email protected]>--- arch/x86/include/asm/kexec.h | 2 ++ arch/x86/kernel/crash.c | 25 +++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 0 deletions(-)arch/x86/include/asm/kexec.h +2
-0@@ -163,6 +163,8 @@ struct kimage_arch { };#endif +extern void (*crash_vmclear_loaded_vmcss)(void ); +#endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_KEXEC_H */ arch/x86/kernel/crash.c +25
-0@@ -16,6 +16,7 @@#include <linux/delay.h> #include <linux/elf.h> #include <linux/elfcore.h> +#include <linux/module.h> #include <asm/processor.h> #include <asm/hardirq.h> @@ -29,6 +30,20 @@#include <asm/virtext.h> int in_crash_kexec; + +/* +* This is used to VMCLEAR all VMCSs loaded on the +* processor. And when loading kvm_intel module, the +* callback function pointer will be assigned. +*/ +void (*crash_vmclear_loaded_vmcss)(void ) =NULL ; +EXPORT_SYMBOL_GPL (crash_vmclear_loaded_vmcss); + +static inline void cpu_emergency_vmclear_loaded_vmcss (void ) +{ +if (crash_vmclear_loaded_vmcss) +crash_vmclear_loaded_vmcss (); +}#if defined(CONFIG_SMP ) && defined(CONFIG_X86_LOCAL_APIC )@@ -46,6 +61,11 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)#endif crash_save_cpu (regs, cpu); +/* +* VMCLEAR VMCSs loaded on all cpus if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Disable VMX or SVM if needed. * * We need to disable virtualization on all CPUs. @@ -88,6 +108,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)kdump_nmi_shootdown_cpus (); +/* +* VMCLEAR VMCSs loaded on this cpu if needed. +*/ +cpu_emergency_vmclear_loaded_vmcss (); +/* Booting kdump kernel with VMX or SVM enabled won't work, * because (among other limitations) we can't disable paging * with the virt flags.
Quoted 8 lines
Quoted 1 line
1.7.1
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Gleb.
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Gleb.
Re: [PATCH v9 1/2] x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
In reply to Zhang YanfeiQuoted 4 lines · Zhang Yanfei
This patch provides a way to VMCLEAR VMCSs related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
Apologies for the delay I have been travelling, and I wanted to at least read through the code.
Overall I think this is good but I have one nit, and I see one real problem with this code.
arch/x86/kernel/crash.c line 46
Quoted 13 lines
arch/x86/kernel/crash.c +13
-0+/* +* This is used to VMCLEAR all VMCSs loaded on the +* processor. And when loading kvm_intel module, the +* callback function pointer will be assigned. +*/ +void (*crash_vmclear_loaded_vmcss)(void ) =NULL ; +EXPORT_SYMBOL_GPL (crash_vmclear_loaded_vmcss); + +static inline void cpu_emergency_vmclear_loaded_vmcss (void ) +{ +if (crash_vmclear_loaded_vmcss) +crash_vmclear_loaded_vmcss (); +}
The nit is the use of emergency instead of crash in the name.
The problem is that this is potentially a NULL pointer dereference if kvm-intel is removed. The easist fix would be in your second patch to just make it impossible to unload the kvm-intel module. Otherwise there the deference of crash_vmclear_loaded_vmcss needs to be rcu protected, with a syncrhonize_rcu after the pointer is set to NULL in the unload path.
Otherwise I have no objections to this code.
Eric
Re: [PATCH v9 1/2] x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
Quoted 13 lines · Eric W. Biederman
Quoted 4 lines · Zhang Yanfei
This patch provides a way to VMCLEAR VMCSs related to guests on all cpus before executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the vmcore updated and non-corrupted.
Apologies for the delay I have been travelling, and I wanted to at least read through the code.
Overall I think this is good but I have one nit, and I see one real problem with this code.
Quoted 15 lines
arch/x86/kernel/crash.c line 46
Quoted 13 lines
arch/x86/kernel/crash.c +13
-0+/* +* This is used to VMCLEAR all VMCSs loaded on the +* processor. And when loading kvm_intel module, the +* callback function pointer will be assigned. +*/ +void (*crash_vmclear_loaded_vmcss)(void ) =NULL ; +EXPORT_SYMBOL_GPL (crash_vmclear_loaded_vmcss); + +static inline void cpu_emergency_vmclear_loaded_vmcss (void ) +{ +if (crash_vmclear_loaded_vmcss) +crash_vmclear_loaded_vmcss (); +}The nit is the use of emergency instead of crash in the name.
ok, emergency -> crash
Quoted 7 lines
The problem is that this is potentially a NULL pointer dereference if kvm-intel is removed. The easist fix would be in your second patch to just make it impossible to unload the kvm-intel module. Otherwise there the deference of
crash_vmclear_loaded_vmcssneeds to be rcu protected, with asyncrhonize_rcuafter the pointer is set to NULL in the unload path.
Ah, thanks for this comment.
I think I will use the rcu machanism to solve the problem.
Quoted 2 lines
Otherwise I have no objections to this code.
Thanks for your review. I will update the patch and resend it.
Thanks
Zhang Yanfei
PATCH v9 2/2 KVM-INTEL: provide the vmclear function and a bitmap to support VMCLEAR in kdump
In reply to Zhang YanfeiThe vmclear function will be assigned to the callback function pointer when loading kvm-intel module. And the bitmap indicates whether we should do VMCLEAR operation in kdump. The bits in the bitmap are set/unset according to different conditions.
--- arch/x86/kvm/vmx.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 65 insertions(+), 0 deletions(-)
arch/x86/kvm/vmx.c +65 -0
@@ -41,6 +41,7 @@#include <asm/i387.h> #include <asm/xcr.h> #include <asm/perf_event.h> +#include <asm/kexec.h> #include "trace.h"
@@ -963,6 +964,46 @@ static void vmcs_load(struct vmcs *vmcs) vmcs, phys_addr); } +#ifdef CONFIG_KEXEC +/* +* This bitmap is used to indicate whether the vmclear +* operation is enabled on all cpus. All disabled by +* default. +*/ +static cpumask_t crash_vmclear_enabled_bitmap =CPU_MASK_NONE ; + +static inline void crash_enable_local_vmclear (int cpu) +{ +cpumask_set_cpu (cpu, &crash_vmclear_enabled_bitmap); +} + +static inline void crash_disable_local_vmclear (int cpu) +{ +cpumask_clear_cpu (cpu, &crash_vmclear_enabled_bitmap); +} + +static inline int crash_local_vmclear_enabled (int cpu) +{ +return cpumask_test_cpu (cpu, &crash_vmclear_enabled_bitmap); +} + +static void crash_vmclear_local_loaded_vmcss (void ) +{ +int cpu =raw_smp_processor_id (); +struct loaded_vmcs *v; + +if (!crash_local_vmclear_enabled (cpu)) +return ; + +list_for_each_entry (v, &per_cpu (loaded_vmcss_on_cpu, cpu), + loaded_vmcss_on_cpu_link) +vmcs_clear (v->vmcs); +} +#else +static inline void crash_enable_local_vmclear (int cpu) { } +static inline void crash_disable_local_vmclear (int cpu) { } +#endif /* CONFIG_KEXEC */ +static void __loaded_vmcs_clear (void *arg) {struct loaded_vmcs *loaded_vmcs = arg;
@@ -972,8 +1013,10 @@ static void __loaded_vmcs_clear(void *arg)return ;/* vcpu migration can race with cpu offline */ if (per_cpu (current_vmcs, cpu) == loaded_vmcs->vmcs)per_cpu (current_vmcs, cpu) =NULL ; +crash_disable_local_vmclear (cpu);list_del (&loaded_vmcs->loaded_vmcss_on_cpu_link);loaded_vmcs_init (loaded_vmcs); +crash_enable_local_vmclear (cpu); }static void loaded_vmcs_clear (struct loaded_vmcs *loaded_vmcs)
@@ -1491,8 +1534,10 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)kvm_make_request (KVM_REQ_TLB_FLUSH , vcpu);local_irq_disable (); +crash_disable_local_vmclear (cpu);list_add (&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link, &per_cpu (loaded_vmcss_on_cpu, cpu)); +crash_enable_local_vmclear (cpu);local_irq_enable ();/*
@@ -2302,6 +2347,18 @@ static int hardware_enable(void *garbage)return -EBUSY ;INIT_LIST_HEAD (&per_cpu (loaded_vmcss_on_cpu, cpu)); + +/* +* Now we can enable the vmclear operation in kdump +* since the loaded_vmcss_on_cpu list on this cpu +* has been initialized. +* +* Though the cpu is not in VMX operation now, there +* is no problem to enable the vmclear operation +* for the loaded_vmcss_on_cpu list is empty! +*/ +crash_enable_local_vmclear (cpu); +rdmsrl (MSR_IA32_FEATURE_CONTROL , old); test_bits =FEATURE_CONTROL_LOCKED ;
@@ -7230,6 +7287,10 @@ static int __init vmx_init(void)if (r) goto out3; +#ifdef CONFIG_KEXEC + crash_vmclear_loaded_vmcss = crash_vmclear_local_loaded_vmcss; +#endif +vmx_disable_intercept_for_msr (MSR_FS_BASE , false);vmx_disable_intercept_for_msr (MSR_GS_BASE , false);vmx_disable_intercept_for_msr (MSR_KERNEL_GS_BASE , true);
@@ -7265,6 +7326,10 @@ static void __exit vmx_exit(void)free_page ((unsigned long )vmx_io_bitmap_b);free_page ((unsigned long )vmx_io_bitmap_a); +#ifdef CONFIG_KEXEC + crash_vmclear_loaded_vmcss =NULL ; +#endif +kvm_exit (); }
Signature · 1 line
1.7.1