lkml.org 
[lkml]   [2022]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 5/7] KVM: x86: never write to memory from kvm_vcpu_check_block
Date
kvm_vcpu_check_block() is called while not in TASK_RUNNING, and therefore
it cannot sleep. Writing to guest memory is therefore forbidden, but it
can happen on AMD processors if kvm_check_nested_events() causes a vmexit.

Fortunately, all events that are caught by kvm_check_nested_events() are
also recognized by kvm_vcpu_has_events() through vendor callbacks such as
kvm_x86_interrupt_allowed() or kvm_x86_ops.nested_ops->has_events(), so
remove the call and postpone the actual processing to vcpu_block().

Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/x86.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5c5341110876..f901cd872b6d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10637,6 +10637,15 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
return 1;
}

+ /*
+ * Evaluate nested events before exiting the halted state. This allows
+ * the halt state to be recorded properly in the VMCS12's activity
+ * state field (AMD does not have a similar field and a VM-Exit always
+ * causes a spurious wakeup from HLT).
+ */
+ if (is_guest_mode(vcpu))
+ kvm_check_nested_events(vcpu);
+
if (kvm_apic_accept_events(vcpu) < 0)
return 0;
switch(vcpu->arch.mp_state) {
@@ -10660,9 +10669,6 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)

static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
{
- if (is_guest_mode(vcpu))
- kvm_check_nested_events(vcpu);
-
return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted);
}
--
2.31.1

\
 
 \ /
  Last update: 2022-08-22 19:09    [W:0.070 / U:0.256 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site