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Commit c94b0cf2 authored by James Morse's avatar James Morse Committed by Will Deacon
Browse files

arm64: hyp/kvm: Make hyp-stub reject kvm_call_hyp() 



A later patch implements kvm_arch_hardware_disable(), to remove kvm
from el2, and re-instate the hyp-stub.

This can happen while guests are running, particularly when kvm_reboot()
calls kvm_arch_hardware_disable() on each cpu. This can interrupt a guest,
remove kvm, then allow the guest to be scheduled again. This causes
kvm_call_hyp() to be run against the hyp-stub.

Change the hyp-stub to return a new exception type when this happens,
and add code to kvm's handle_exit() to tell userspace we failed to
enter the guest.

Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent ad72e59f

arch/arm64/include/asm/kvm_asm.h

+2 −0
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ 


#define ARM_EXCEPTION_IRQ	  0

#define ARM_EXCEPTION_TRAP	  1

/* The hyp-stub will return this for any kvm_call_hyp() call */

#define ARM_EXCEPTION_HYP_GONE	  2



#define KVM_ARM64_DEBUG_DIRTY_SHIFT	0

#define KVM_ARM64_DEBUG_DIRTY		(1 << KVM_ARM64_DEBUG_DIRTY_SHIFT)

arch/arm64/kernel/hyp-stub.S

+3 −2
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 


#include <asm/assembler.h>

#include <asm/kvm_arm.h>

#include <asm/kvm_asm.h>

#include <asm/ptrace.h>

#include <asm/virt.h>
@@ -70,8 +71,8 @@ el1_sync: 
	msr	vbar_el2, x1

	b	9f



	/* Unrecognised call type */

2:	mov     x0, xzr

	/* Someone called kvm_call_hyp() against the hyp-stub... */

2:	mov     x0, #ARM_EXCEPTION_HYP_GONE



9:	eret

ENDPROC(el1_sync)

arch/arm64/kvm/handle_exit.c

+7 −0
Original line number Diff line number Diff line
@@ -186,6 +186,13 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run, 
		exit_handler = kvm_get_exit_handler(vcpu);



		return exit_handler(vcpu, run);

	case ARM_EXCEPTION_HYP_GONE:

		/*

		 * EL2 has been reset to the hyp-stub. This happens when a guest

		 * is pre-empted by kvm_reboot()'s shutdown call.

		 */

		run->exit_reason = KVM_EXIT_FAIL_ENTRY;

		return 0;

	default:

		kvm_pr_unimpl("Unsupported exception type: %d",

			      exception_index);