[PATCH v3 02/15] KVM: arm64: Add helpers for ESR_ELx_ERET_ISS_ERET*

Marc Zyngier
2024-03-21T15:54:32Z

The ESR_ELx_ERET_ISS_ERET* macros are a bit confusing:

- ESR_ELx_ERET_ISS_ERET really indicates that we have trapped an
ERETA* instruction, as opposed to an ERET

- ESR_ELx_ERET_ISS_ERETA really indicates that we have trapped
an ERETAB instruction, as opposed to an ERETAA.

We could repaint those to make more sense, but these are the
names that are present in the ARM ARM, and we are sentimentally
attached to those.

Instead, add two new helpers:

- esr_iss_is_eretax() being true tells you that you need to
authenticate the ERET

- esr_iss_is_eretab() tells you that you need to use the B key
instead of the A key

Following patches will make use of these primitives.

Suggested-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/esr.h | 12 ++++++++++++
arch/arm64/kvm/handle_exit.c | 2 +-
2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 353fe08546cf..98008c16025e 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -407,6 +407,18 @@ static inline bool esr_fsc_is_access_flag_fault(unsigned long esr)
return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_ACCESS;
}

+/* Indicate whether ESR.EC==0x1A is for an ERETAx instruction */
+static inline bool esr_iss_is_eretax(unsigned long esr)
+{
+ return esr & ESR_ELx_ERET_ISS_ERET;
+}
+
+/* Indicate which key is used for ERETAx (false: A-Key, true: B-Key) */
+static inline bool esr_iss_is_eretab(unsigned long esr)
+{
+ return esr & ESR_ELx_ERET_ISS_ERETA;
+}
+
const char *esr_get_class_string(unsigned long esr);
#endif /* __ASSEMBLY */

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 617ae6dea5d5..15221e481ccd 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -219,7 +219,7 @@ static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu)

static int kvm_handle_eret(struct kvm_vcpu *vcpu)
{
- if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_ERET_ISS_ERET)
+ if (esr_iss_is_eretax(kvm_vcpu_get_esr(vcpu)))
return kvm_handle_ptrauth(vcpu);

/*
--
2.39.2