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Commit e3feebf8 authored by Alex Bennée's avatar Alex Bennée Committed by Christoffer Dall
Browse files

kvm: arm64: handle single-step of hyp emulated mmio instructions 



There is a fast-path of MMIO emulation inside hyp mode. The handling
of single-step is broadly the same as kvm_arm_handle_step_debug()
except we just setup ESR/HSR so handle_exit() does the correct thing
as we exit.

For the case of an emulated illegal access causing an SError we will
exit via the ARM_EXCEPTION_EL1_SERROR path in handle_exit(). We behave
as we would during a real SError and clear the DBG_SPSR_SS bit for the
emulated instruction.

Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent e70dce73

arch/arm64/kvm/hyp/switch.c

+30 −7
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <asm/kvm_emulate.h>

#include <asm/kvm_hyp.h>

#include <asm/fpsimd.h>

#include <asm/debug-monitors.h>



static bool __hyp_text __fpsimd_enabled_nvhe(void)

{
@@ -269,7 +270,11 @@ static bool __hyp_text __populate_fault_info(struct kvm_vcpu *vcpu) 
	return true;

}



static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu)

/* Skip an instruction which has been emulated. Returns true if

 * execution can continue or false if we need to exit hyp mode because

 * single-step was in effect.

 */

static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu)

{

	*vcpu_pc(vcpu) = read_sysreg_el2(elr);
@@ -282,6 +287,14 @@ static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu) 
	}



	write_sysreg_el2(*vcpu_pc(vcpu), elr);



	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {

		vcpu->arch.fault.esr_el2 =

			(ESR_ELx_EC_SOFTSTP_LOW << ESR_ELx_EC_SHIFT) | 0x22;

		return false;

	} else {

		return true;

	}

}



int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
@@ -342,13 +355,21 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) 
			int ret = __vgic_v2_perform_cpuif_access(vcpu);



			if (ret == 1) {

				__skip_instr(vcpu);

				if (__skip_instr(vcpu))

					goto again;

				else

					exit_code = ARM_EXCEPTION_TRAP;

			}



			if (ret == -1) {

				/* Promote an illegal access to an SError */

				__skip_instr(vcpu);

				/* Promote an illegal access to an

				 * SError. If we would be returning

				 * due to single-step clear the SS

				 * bit so handle_exit knows what to

				 * do after dealing with the error.

				 */

				if (!__skip_instr(vcpu))

					*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;

				exit_code = ARM_EXCEPTION_EL1_SERROR;

			}
@@ -363,8 +384,10 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) 
		int ret = __vgic_v3_perform_cpuif_access(vcpu);



		if (ret == 1) {

			__skip_instr(vcpu);

			if (__skip_instr(vcpu))

				goto again;

			else

				exit_code = ARM_EXCEPTION_TRAP;

		}



		/* 0 falls through to be handled out of EL2 */