From: Andrew Jones <drjones@redhat.com>

Date: Sun, 4 Jun 2017 14:43:54 +0200

Subject: KVM: arm/arm64: properly use vcpu requests

Patch-mainline: v4.13-rc1

Git-commit: 6a6d73be12fbe492d0678cd84d3b35e2bc9698e4

References: bsc#1077761

arm/arm64 already has one VCPU request used when setting pause,

but it doesn't properly check requests in VCPU RUN. Check it

and also make sure we set vcpu->mode at the appropriate time

(before the check) and with the appropriate barriers. See

Documentation/virtual/kvm/vcpu-requests.rst. Also make sure we

don't leave any vcpu requests we don't intend to handle later

set in the request bitmap. If we don't clear them, then

kvm_request_pending() may return true when it shouldn't.

Using VCPU requests properly fixes a small race where pause

could get set just as a VCPU was entering guest mode.

Signed-off-by: Andrew Jones <drjones@redhat.com>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

Signed-off-by: Christoffer Dall <cdall@linaro.org>

Acked-by: Alexander Graf <agraf@suse.de>

---

 arch/arm/kvm/handle_exit.c   |    1 +

 arch/arm64/kvm/handle_exit.c |    1 +

 virt/kvm/arm/arm.c           |   14 ++++++++++++--

 virt/kvm/arm/psci.c          |    1 +

 4 files changed, 15 insertions(+), 2 deletions(-)

--- a/arch/arm/kvm/handle_exit.c

+++ b/arch/arm/kvm/handle_exit.c

@@ -72,6 +72,7 @@

 		trace_kvm_wfx(*vcpu_pc(vcpu), false);

 		vcpu->stat.wfi_exit_stat++;

 		kvm_vcpu_block(vcpu);

+		kvm_clear_request(KVM_REQ_UNHALT, vcpu);

 	}

 	kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));

--- a/arch/arm64/kvm/handle_exit.c

+++ b/arch/arm64/kvm/handle_exit.c

@@ -89,6 +89,7 @@

 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);

 		vcpu->stat.wfi_exit_stat++;

 		kvm_vcpu_block(vcpu);

+		kvm_clear_request(KVM_REQ_UNHALT, vcpu);

 	}

 	kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));

--- a/virt/kvm/arm/arm.c

+++ b/virt/kvm/arm/arm.c

@@ -546,6 +546,7 @@

 	kvm_for_each_vcpu(i, vcpu, kvm) {

 		vcpu->arch.pause = false;

+		kvm_clear_request(KVM_REQ_VCPU_EXIT, vcpu);

 		swake_up(kvm_arch_vcpu_wq(vcpu));

 	}

 }

@@ -638,8 +639,18 @@

 			run->exit_reason = KVM_EXIT_INTR;

 		}

+		/*

+		 * Ensure we set mode to IN_GUEST_MODE after we disable

+		 * interrupts and before the final VCPU requests check.

+		 * See the comment in kvm_vcpu_exiting_guest_mode() and

+		 * Documentation/virtual/kvm/vcpu-requests.rst

+		 */

+		smp_store_mb(vcpu->mode, IN_GUEST_MODE);

+

 		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||

-			vcpu->arch.power_off || vcpu->arch.pause) {

+		    kvm_request_pending(vcpu) ||

+		    vcpu->arch.power_off || vcpu->arch.pause) {

+			vcpu->mode = OUTSIDE_GUEST_MODE;

 			local_irq_enable();

 			kvm_pmu_sync_hwstate(vcpu);

 			kvm_timer_sync_hwstate(vcpu);

@@ -655,7 +666,6 @@

 		 */

 		trace_kvm_entry(*vcpu_pc(vcpu));

 		guest_enter_irqoff();

-		vcpu->mode = IN_GUEST_MODE;

 		ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);

--- a/virt/kvm/arm/psci.c

+++ b/virt/kvm/arm/psci.c

@@ -57,6 +57,7 @@

 	 * for KVM will preserve the register state.

 	 */

 	kvm_vcpu_block(vcpu);

+	kvm_clear_request(KVM_REQ_UNHALT, vcpu);

 	return PSCI_RET_SUCCESS;

 }