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KVM: VMX: Move preemption timer <=> hrtimer dance to common x86

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commit 98c25ead5eda5e9d41abe57839ad3e8caf19500c upstream.

Handle the switch to/from the hypervisor/software timer when a vCPU is
blocking in common x86 instead of in VMX.  Even though VMX is the only
user of a hypervisor timer, the logic and all functions involved are
generic x86 (unless future CPUs do something completely different and
implement a hypervisor timer that runs regardless of mode).

Handling the switch in common x86 will allow for the elimination of the
pre/post_blocks hooks, and also lets KVM switch back to the hypervisor
timer if and only if it was in use (without additional params).  Add a
comment explaining why the switch cannot be deferred to kvm_sched_out()
or kvm_vcpu_block().

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20211208015236.1616697-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's
suggestion. Add Reported-by and Link tags.]
Reported-by: syzbot+b6a74be92b5063a0f1ff@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605
Tested-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-12-08 01:52:17 +00:00 committed by Greg Kroah-Hartman
parent a58d4e6671
commit 4483dc41d1
2 changed files with 21 additions and 6 deletions
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6
arch/x86/kvm/vmx/vmx.c
View File

@ -7597,17 +7597,11 @@ static int vmx_pre_block(struct kvm_vcpu *vcpu)
if (pi_pre_block(vcpu))
return 1;
if (kvm_lapic_hv_timer_in_use(vcpu))
kvm_lapic_switch_to_sw_timer(vcpu);
return 0;
}
static void vmx_post_block(struct kvm_vcpu *vcpu)
{
if (kvm_x86_ops.set_hv_timer)
kvm_lapic_switch_to_hv_timer(vcpu);
pi_post_block(vcpu);
}

21
arch/x86/kvm/x86.c
View File

@ -10043,12 +10043,28 @@ out:
static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
{
bool hv_timer;
if (!kvm_arch_vcpu_runnable(vcpu) &&
(!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) {
/*
* Switch to the software timer before halt-polling/blocking as
* the guest's timer may be a break event for the vCPU, and the
* hypervisor timer runs only when the CPU is in guest mode.
* Switch before halt-polling so that KVM recognizes an expired
* timer before blocking.
*/
hv_timer = kvm_lapic_hv_timer_in_use(vcpu);
if (hv_timer)
kvm_lapic_switch_to_sw_timer(vcpu);
srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
kvm_vcpu_block(vcpu);
vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
if (hv_timer)
kvm_lapic_switch_to_hv_timer(vcpu);
if (kvm_x86_ops.post_block)
static_call(kvm_x86_post_block)(vcpu);
@ -10287,6 +10303,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
r = -EINTR;
goto out;
}
/*
* It should be impossible for the hypervisor timer to be in
* use before KVM has ever run the vCPU.
*/
WARN_ON_ONCE(kvm_lapic_hv_timer_in_use(vcpu));
kvm_vcpu_block(vcpu);
if (kvm_apic_accept_events(vcpu) < 0) {
r = 0;