Commit d2b2ecba authored by Jintack Lim's avatar Jintack Lim Committed by Oliver Upton
Browse files

KVM: arm64: nv: Forward FP/ASIMD traps to guest hypervisor 



Give precedence to the guest hypervisor's trap configuration when
routing an FP/ASIMD trap taken to EL2. Take advantage of the
infrastructure for translating CPTR_EL2 into the VHE (i.e. EL1) format
and base the trap decision solely on the VHE view of the register. The
in-memory value of CPTR_EL2 will always be up to date for the guest
hypervisor (more on that later), so just read it directly from memory.

Bury all of this behind a macro keyed off of the CPTR bitfield in
anticipation of supporting other traps (e.g. SVE).

[maz: account for HCR_EL2.E2H when testing for TFP/FPEN, with
 all the hard work actually being done by Chase Conklin]
[ oliver: translate nVHE->VHE format for testing traps; macro for reuse
 in other CPTR_EL2.xEN fields ]

Signed-off-by: default avatarJintack Lim <jintack.lim@linaro.org>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@arm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240620164653.1130714-2-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 83a7eefe

arch/arm64/include/asm/kvm_emulate.h

+43 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#ifndef __ARM64_KVM_EMULATE_H__

#define __ARM64_KVM_EMULATE_H__



#include <linux/bitfield.h>

#include <linux/kvm_host.h>



#include <asm/debug-monitors.h>
@@ -660,4 +661,46 @@ static __always_inline void kvm_reset_cptr_el2(struct kvm_vcpu *vcpu) 


	kvm_write_cptr_el2(val);

}



/*

 * Returns a 'sanitised' view of CPTR_EL2, translating from nVHE to the VHE

 * format if E2H isn't set.

 */

static inline u64 vcpu_sanitised_cptr_el2(const struct kvm_vcpu *vcpu)

{

	u64 cptr = __vcpu_sys_reg(vcpu, CPTR_EL2);



	if (!vcpu_el2_e2h_is_set(vcpu))

		cptr = translate_cptr_el2_to_cpacr_el1(cptr);



	return cptr;

}



static inline bool ____cptr_xen_trap_enabled(const struct kvm_vcpu *vcpu,

					     unsigned int xen)

{

	switch (xen) {

	case 0b00:

	case 0b10:

		return true;

	case 0b01:

		return vcpu_el2_tge_is_set(vcpu) && !vcpu_is_el2(vcpu);

	case 0b11:

	default:

		return false;

	}

}



#define __guest_hyp_cptr_xen_trap_enabled(vcpu, xen)				\

	(!vcpu_has_nv(vcpu) ? false :						\

	 ____cptr_xen_trap_enabled(vcpu,					\

				   SYS_FIELD_GET(CPACR_ELx, xen,		\

						 vcpu_sanitised_cptr_el2(vcpu))))



static inline bool guest_hyp_fpsimd_traps_enabled(const struct kvm_vcpu *vcpu)

{

	return __guest_hyp_cptr_xen_trap_enabled(vcpu, FPEN);

}





#endif /* __ARM64_KVM_EMULATE_H__ */

arch/arm64/kvm/handle_exit.c

+12 −4
Original line number Diff line number Diff line
@@ -94,11 +94,19 @@ static int handle_smc(struct kvm_vcpu *vcpu) 
}



/*

 * Guest access to FP/ASIMD registers are routed to this handler only

 * when the system doesn't support FP/ASIMD.

 * This handles the cases where the system does not support FP/ASIMD or when

 * we are running nested virtualization and the guest hypervisor is trapping

 * FP/ASIMD accesses by its guest guest.

 *

 * All other handling of guest vs. host FP/ASIMD register state is handled in

 * fixup_guest_exit().

 */

static int handle_no_fpsimd(struct kvm_vcpu *vcpu)

static int kvm_handle_fpasimd(struct kvm_vcpu *vcpu)

{

	if (guest_hyp_fpsimd_traps_enabled(vcpu))

		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));



	/* This is the case when the system doesn't support FP/ASIMD. */

	kvm_inject_undefined(vcpu);

	return 1;

}
@@ -304,7 +312,7 @@ static exit_handle_fn arm_exit_handlers[] = { 
	[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,

	[ESR_ELx_EC_BKPT32]	= kvm_handle_guest_debug,

	[ESR_ELx_EC_BRK64]	= kvm_handle_guest_debug,

	[ESR_ELx_EC_FP_ASIMD]	= handle_no_fpsimd,

	[ESR_ELx_EC_FP_ASIMD]	= kvm_handle_fpasimd,

	[ESR_ELx_EC_PAC]	= kvm_handle_ptrauth,

};

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

+3 −0
Original line number Diff line number Diff line
@@ -354,6 +354,9 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code) 
	/* Only handle traps the vCPU can support here: */

	switch (esr_ec) {

	case ESR_ELx_EC_FP_ASIMD:

		/* Forward traps to the guest hypervisor as required */

		if (guest_hyp_fpsimd_traps_enabled(vcpu))

			return false;

		break;

	case ESR_ELx_EC_SVE:

		if (!sve_guest)