Commit 9b661950 authored by Mark Rutland's avatar Mark Rutland Committed by Marc Zyngier
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KVM: arm64: Refactor exit handlers 



The hyp exit handling logic is largely shared between VHE and nVHE/hVHE,
with common logic in arch/arm64/kvm/hyp/include/hyp/switch.h. The code
in the header depends on function definitions provided by
arch/arm64/kvm/hyp/vhe/switch.c and arch/arm64/kvm/hyp/nvhe/switch.c
when they include the header.

This is an unusual header dependency, and prevents the use of
arch/arm64/kvm/hyp/include/hyp/switch.h in other files as this would
result in compiler warnings regarding missing definitions, e.g.

| In file included from arch/arm64/kvm/hyp/nvhe/hyp-main.c:8:
| ./arch/arm64/kvm/hyp/include/hyp/switch.h:733:31: warning: 'kvm_get_exit_handler_array' used but never defined
|   733 | static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu);
|       |                               ^~~~~~~~~~~~~~~~~~~~~~~~~~
| ./arch/arm64/kvm/hyp/include/hyp/switch.h:735:13: warning: 'early_exit_filter' used but never defined
|   735 | static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code);
|       |             ^~~~~~~~~~~~~~~~~

Refactor the logic such that the header doesn't depend on anything from
the C files. There should be no functional change as a result of this
patch.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarMark Brown <broonie@kernel.org>
Tested-by: default avatarMark Brown <broonie@kernel.org>
Acked-by: default avatarWill Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-7-mark.rutland@arm.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent ee14db31

arch/arm64/kvm/hyp/include/hyp/switch.h

+6 −24
Original line number Diff line number Diff line
@@ -679,23 +679,16 @@ static bool kvm_hyp_handle_dabt_low(struct kvm_vcpu *vcpu, u64 *exit_code) 


typedef bool (*exit_handler_fn)(struct kvm_vcpu *, u64 *);



static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu);



static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code);



/*

 * Allow the hypervisor to handle the exit with an exit handler if it has one.

 *

 * Returns true if the hypervisor handled the exit, and control should go back

 * to the guest, or false if it hasn't.

 */

static inline bool kvm_hyp_handle_exit(struct kvm_vcpu *vcpu, u64 *exit_code)

static inline bool kvm_hyp_handle_exit(struct kvm_vcpu *vcpu, u64 *exit_code,

				       const exit_handler_fn *handlers)

{

	const exit_handler_fn *handlers = kvm_get_exit_handler_array(vcpu);

	exit_handler_fn fn;



	fn = handlers[kvm_vcpu_trap_get_class(vcpu)];



	exit_handler_fn fn = handlers[kvm_vcpu_trap_get_class(vcpu)];

	if (fn)

		return fn(vcpu, exit_code);
@@ -725,20 +718,9 @@ static inline void synchronize_vcpu_pstate(struct kvm_vcpu *vcpu, u64 *exit_code 
 * the guest, false when we should restore the host state and return to the

 * main run loop.

 */

static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)

static inline bool __fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code,

				      const exit_handler_fn *handlers)

{

	/*

	 * Save PSTATE early so that we can evaluate the vcpu mode

	 * early on.

	 */

	synchronize_vcpu_pstate(vcpu, exit_code);



	/*

	 * Check whether we want to repaint the state one way or

	 * another.

	 */

	early_exit_filter(vcpu, exit_code);



	if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)

		vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
@@ -768,7 +750,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code) 
		goto exit;



	/* Check if there's an exit handler and allow it to handle the exit. */

	if (kvm_hyp_handle_exit(vcpu, exit_code))

	if (kvm_hyp_handle_exit(vcpu, exit_code, handlers))

		goto guest;

exit:

	/* Return to the host kernel and handle the exit */

arch/arm64/kvm/hyp/nvhe/switch.c

+16 −12
Original line number Diff line number Diff line
@@ -250,19 +250,21 @@ static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu) 
	return hyp_exit_handlers;

}



static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)

{

	const exit_handler_fn *handlers = kvm_get_exit_handler_array(vcpu);



	synchronize_vcpu_pstate(vcpu, exit_code);



	/*

 * Some guests (e.g., protected VMs) are not be allowed to run in AArch32.

 * The ARMv8 architecture does not give the hypervisor a mechanism to prevent a

 * guest from dropping to AArch32 EL0 if implemented by the CPU. If the

 * hypervisor spots a guest in such a state ensure it is handled, and don't

 * trust the host to spot or fix it.  The check below is based on the one in

	 * Some guests (e.g., protected VMs) are not be allowed to run in

	 * AArch32.  The ARMv8 architecture does not give the hypervisor a

	 * mechanism to prevent a guest from dropping to AArch32 EL0 if

	 * implemented by the CPU. If the hypervisor spots a guest in such a

	 * state ensure it is handled, and don't trust the host to spot or fix

	 * it.  The check below is based on the one in

	 * kvm_arch_vcpu_ioctl_run().

 *

 * Returns false if the guest ran in AArch32 when it shouldn't have, and

 * thus should exit to the host, or true if a the guest run loop can continue.

	 */

static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)

{

	if (unlikely(vcpu_is_protected(vcpu) && vcpu_mode_is_32bit(vcpu))) {

		/*

		 * As we have caught the guest red-handed, decide that it isn't
@@ -275,6 +277,8 @@ static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code) 
		*exit_code &= BIT(ARM_EXIT_WITH_SERROR_BIT);

		*exit_code |= ARM_EXCEPTION_IL;

	}



	return __fixup_guest_exit(vcpu, exit_code, handlers);

}



/* Switch to the guest for legacy non-VHE systems */

arch/arm64/kvm/hyp/vhe/switch.c

+4 −5
Original line number Diff line number Diff line
@@ -540,13 +540,10 @@ static const exit_handler_fn hyp_exit_handlers[] = { 
	[ESR_ELx_EC_MOPS]		= kvm_hyp_handle_mops,

};



static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu)

static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)

{

	return hyp_exit_handlers;

}

	synchronize_vcpu_pstate(vcpu, exit_code);



static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)

{

	/*

	 * If we were in HYP context on entry, adjust the PSTATE view

	 * so that the usual helpers work correctly.
@@ -566,6 +563,8 @@ static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code) 
		*vcpu_cpsr(vcpu) &= ~(PSR_MODE_MASK | PSR_MODE32_BIT);

		*vcpu_cpsr(vcpu) |= mode;

	}



	return __fixup_guest_exit(vcpu, exit_code, hyp_exit_handlers);

}



/* Switch to the guest for VHE systems running in EL2 */