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x86/kvm: Disable all PV features on crash 

Crash shutdown handler only disables kvmclock and steal time, other PV
features remain active so we risk corrupting memory or getting some
side-effects in kdump kernel. Move crash handler to kvm.c and unify
with CPU offline.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-5-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2021-04-14 14:35:43 +02:00 committed by Paolo Bonzini
parent c02027b574
commit 3d6b84132d
3 changed files with 32 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/include/asm/kvm_para.h
View File

@ -92,7 +92,6 @@ unsigned int kvm_arch_para_hints(void);
void kvm_async_pf_task_wait_schedule(u32 token);
void kvm_async_pf_task_wake(u32 token);
u32 kvm_read_and_reset_apf_flags(void);
void kvm_disable_steal_time(void);
bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token);
DECLARE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@ -137,11 +136,6 @@ static inline u32 kvm_read_and_reset_apf_flags(void)
return 0;
}
static inline void kvm_disable_steal_time(void)
{
return;
}
static __always_inline bool kvm_handle_async_pf(struct pt_regs *regs, u32 token)
{
return false;

44
arch/x86/kernel/kvm.c
View File

@ -38,6 +38,7 @@
#include <asm/tlb.h>
#include <asm/cpuidle_haltpoll.h>
#include <asm/ptrace.h>
#include <asm/reboot.h>
#include <asm/svm.h>
DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@ -375,6 +376,14 @@ static void kvm_pv_disable_apf(void)
pr_info("disable async PF for cpu %d\n", smp_processor_id());
}
static void kvm_disable_steal_time(void)
{
if (!has_steal_clock)
return;
wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}
static void kvm_pv_guest_cpu_reboot(void *unused)
{
/*
@ -417,14 +426,6 @@ static u64 kvm_steal_clock(int cpu)
return steal;
}
void kvm_disable_steal_time(void)
{
if (!has_steal_clock)
return;
wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}
static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
{
early_set_memory_decrypted((unsigned long) ptr, size);
@ -452,13 +453,14 @@ static void __init sev_map_percpu_data(void)
}
}
static void kvm_guest_cpu_offline(void)
static void kvm_guest_cpu_offline(bool shutdown)
{
kvm_disable_steal_time();
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
wrmsrl(MSR_KVM_PV_EOI_EN, 0);
kvm_pv_disable_apf();
apf_task_wake_all();
if (!shutdown)
apf_task_wake_all();
kvmclock_disable();
}
@ -661,7 +663,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
unsigned long flags;
local_irq_save(flags);
kvm_guest_cpu_offline();
kvm_guest_cpu_offline(false);
local_irq_restore(flags);
return 0;
}
@ -670,7 +672,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
static int kvm_suspend(void)
{
kvm_guest_cpu_offline();
kvm_guest_cpu_offline(false);
return 0;
}
@ -685,6 +687,20 @@ static struct syscore_ops kvm_syscore_ops = {
.resume = kvm_resume,
};
/*
* After a PV feature is registered, the host will keep writing to the
* registered memory location. If the guest happens to shutdown, this memory
* won't be valid. In cases like kexec, in which you install a new kernel, this
* means a random memory location will be kept being written.
*/
#ifdef CONFIG_KEXEC_CORE
static void kvm_crash_shutdown(struct pt_regs *regs)
{
kvm_guest_cpu_offline(true);
native_machine_crash_shutdown(regs);
}
#endif
static void __init kvm_guest_init(void)
{
int i;
@ -727,6 +743,10 @@ static void __init kvm_guest_init(void)
kvm_guest_cpu_init();
#endif
#ifdef CONFIG_KEXEC_CORE
machine_ops.crash_shutdown = kvm_crash_shutdown;
#endif
register_syscore_ops(&kvm_syscore_ops);
/*

21
arch/x86/kernel/kvmclock.c
View File

@ -20,7 +20,6 @@
#include <asm/hypervisor.h>
#include <asm/mem_encrypt.h>
#include <asm/x86_init.h>
#include <asm/reboot.h>
#include <asm/kvmclock.h>
static int kvmclock __initdata = 1;
@ -203,23 +202,6 @@ static void kvm_setup_secondary_clock(void)
}
#endif
/*
* After the clock is registered, the host will keep writing to the
* registered memory location. If the guest happens to shutdown, this memory
* won't be valid. In cases like kexec, in which you install a new kernel, this
* means a random memory location will be kept being written. So before any
* kind of shutdown from our side, we unregister the clock by writing anything
* that does not have the 'enable' bit set in the msr
*/
#ifdef CONFIG_KEXEC_CORE
static void kvm_crash_shutdown(struct pt_regs *regs)
{
native_write_msr(msr_kvm_system_time, 0, 0);
kvm_disable_steal_time();
native_machine_crash_shutdown(regs);
}
#endif
void kvmclock_disable(void)
{
native_write_msr(msr_kvm_system_time, 0, 0);
@ -349,9 +331,6 @@ void __init kvmclock_init(void)
#endif
x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
#ifdef CONFIG_KEXEC_CORE
machine_ops.crash_shutdown = kvm_crash_shutdown;
#endif
kvm_get_preset_lpj();
/*