Commit 85738e05 authored by Julien Thierry's avatar Julien Thierry Committed by Catalin Marinas
Browse files

arm64: kvm: Unmask PMR before entering guest 



Interrupts masked by ICC_PMR_EL1 will not be signaled to the CPU. This
means that hypervisor will not receive masked interrupts while running a
guest.

We need to make sure that all maskable interrupts are masked from the
time we call local_irq_disable() in the main run loop, and remain so
until we call local_irq_enable() after returning from the guest, and we
need to ensure that we see no interrupts at all (including pseudo-NMIs)
in the middle of the VM world-switch, while at the same time we need to
ensure we exit the guest when there are interrupts for the host.

We can accomplish this with pseudo-NMIs enabled by:
  (1) local_irq_disable: set the priority mask
  (2) enter guest: set PSTATE.I
  (3)              clear the priority mask
  (4) eret to guest
  (5) exit guest:  set the priotiy mask
                   clear PSTATE.I (and restore other host PSTATE bits)
  (6) local_irq_enable: clear the priority mask.

Signed-off-by: default avatarJulien Thierry <julien.thierry@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: default avatarChristoffer Dall <christoffer.dall@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent a9806aa2

arch/arm64/include/asm/kvm_host.h

+16 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 


#include <linux/types.h>

#include <linux/kvm_types.h>

#include <asm/arch_gicv3.h>

#include <asm/cpufeature.h>

#include <asm/daifflags.h>

#include <asm/fpsimd.h>
@@ -474,10 +475,25 @@ static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) 
static inline void kvm_arm_vhe_guest_enter(void)

{

	local_daif_mask();



	/*

	 * Having IRQs masked via PMR when entering the guest means the GIC

	 * will not signal the CPU of interrupts of lower priority, and the

	 * only way to get out will be via guest exceptions.

	 * Naturally, we want to avoid this.

	 */

	if (system_uses_irq_prio_masking()) {

		gic_write_pmr(GIC_PRIO_IRQON);

		dsb(sy);

	}

}



static inline void kvm_arm_vhe_guest_exit(void)

{

	/*

	 * local_daif_restore() takes care to properly restore PSTATE.DAIF

	 * and the GIC PMR if the host is using IRQ priorities.

	 */

	local_daif_restore(DAIF_PROCCTX_NOIRQ);



	/*

arch/arm64/kvm/hyp/switch.c

+16 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 


#include <kvm/arm_psci.h>



#include <asm/arch_gicv3.h>

#include <asm/cpufeature.h>

#include <asm/kvm_asm.h>

#include <asm/kvm_emulate.h>
@@ -521,6 +522,17 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu) 
	struct kvm_cpu_context *guest_ctxt;

	u64 exit_code;



	/*

	 * Having IRQs masked via PMR when entering the guest means the GIC

	 * will not signal the CPU of interrupts of lower priority, and the

	 * only way to get out will be via guest exceptions.

	 * Naturally, we want to avoid this.

	 */

	if (system_uses_irq_prio_masking()) {

		gic_write_pmr(GIC_PRIO_IRQON);

		dsb(sy);

	}



	vcpu = kern_hyp_va(vcpu);



	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
@@ -573,6 +585,10 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu) 
	 */

	__debug_switch_to_host(vcpu);



	/* Returning to host will clear PSR.I, remask PMR if needed */

	if (system_uses_irq_prio_masking())

		gic_write_pmr(GIC_PRIO_IRQOFF);



	return exit_code;

}

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