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x86/kvm: Move context tracking where it belongs

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Context tracking for KVM happens way too early in the vcpu_run()
code. Anything after guest_enter_irqoff() and before guest_exit_irqoff()
cannot use RCU and should also be not instrumented.

The current way of doing this covers way too much code. Move it closer to
the actual vmenter/exit code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200708195321.724574345@linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Thomas Gleixner 2020-07-08 21:51:54 +02:00 committed by Paolo Bonzini
parent 841c2be09f
commit 87fa7f3e98
3 changed files with 26 additions and 2 deletions
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16
arch/x86/kvm/svm/svm.c
View File

@ -3398,6 +3398,14 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
*/
x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl);
/*
* Tell context tracking that this CPU is about to enter guest
* mode. This has to be after x86_spec_ctrl_set_guest() because
* that can take locks (lockdep needs RCU) and calls into world and
* some more.
*/
guest_enter_irqoff();
__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);
#ifdef CONFIG_X86_64
@ -3408,6 +3416,14 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
loadsegment(gs, svm->host.gs);
#endif
#endif
/*
* Tell context tracking that this CPU is back.
*
* This needs to be done before the below as native_read_msr()
* contains a tracepoint and x86_spec_ctrl_restore_host() calls
* into world and some more.
*/
guest_exit_irqoff();
/*
* We do not use IBRS in the kernel. If this vCPU has used the

10
arch/x86/kvm/vmx/vmx.c
View File

@ -6731,6 +6731,11 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
*/
x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);
/*
* Tell context tracking that this CPU is about to enter guest mode.
*/
guest_enter_irqoff();
/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
@ -6745,6 +6750,11 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
vcpu->arch.cr2 = read_cr2();
/*
* Tell context tracking that this CPU is back.
*/
guest_exit_irqoff();
/*
* We do not use IBRS in the kernel. If this vCPU has used the
* SPEC_CTRL MSR it may have left it on; save the value and

2
arch/x86/kvm/x86.c
View File

@ -8522,7 +8522,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
}
trace_kvm_entry(vcpu->vcpu_id);
guest_enter_irqoff();
fpregs_assert_state_consistent();
if (test_thread_flag(TIF_NEED_FPU_LOAD))
@ -8585,7 +8584,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
local_irq_disable();
kvm_after_interrupt(vcpu);
guest_exit_irqoff();
if (lapic_in_kernel(vcpu)) {
s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
if (delta != S64_MIN) {