From: Christoffer Dall <christoffer.d...@arm.com>

When a guest hypervisor running virtual EL2 in EL1 executes an ERET
instruction, we will have set HCR_EL2.NV which traps ERET to EL2, so
that we can emulate the exception return in software.

Signed-off-by: Christoffer Dall <christoffer.d...@arm.com>
Signed-off-by: Marc Zyngier <m...@kernel.org>
---
 arch/arm64/include/asm/esr.h     |  5 +++++
 arch/arm64/include/asm/kvm_arm.h |  2 +-
 arch/arm64/kvm/handle_exit.c     | 10 ++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 22c81f1edda2..ab63b7b3ea14 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -251,6 +251,11 @@
                (((e) & ESR_ELx_SYS64_ISS_OP2_MASK) >>          \
                 ESR_ELx_SYS64_ISS_OP2_SHIFT))
 
+/* ISS field definitions for ERET/ERETAA/ERETAB trapping */
+
+#define ESR_ELx_ERET_ISS_ERET_ERETAx   0x2
+#define ESR_ELx_ERET_ISS_ERETA_ERATAB  0x1
+
 /*
  * ISS field definitions for floating-point exception traps
  * (FP_EXC_32/FP_EXC_64).
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index e9e10e498785..4cf745f79985 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -326,7 +326,7 @@
        ECN(SP_ALIGN), ECN(FP_EXC32), ECN(FP_EXC64), ECN(SERROR), \
        ECN(BREAKPT_LOW), ECN(BREAKPT_CUR), ECN(SOFTSTP_LOW), \
        ECN(SOFTSTP_CUR), ECN(WATCHPT_LOW), ECN(WATCHPT_CUR), \
-       ECN(BKPT32), ECN(VECTOR32), ECN(BRK64)
+       ECN(BKPT32), ECN(VECTOR32), ECN(BRK64), ECN(ERET)
 
 #define CPACR_EL1_FPEN         (3 << 20)
 #define CPACR_EL1_TTA          (1 << 28)
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 5245ac818e4f..56f8a77b9d4a 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -183,6 +183,15 @@ static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu)
        return 1;
 }
 
+static int kvm_handle_eret(struct kvm_vcpu *vcpu)
+{
+       if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_ERET_ISS_ERET_ERETAx)
+               return kvm_handle_ptrauth(vcpu);
+
+       kvm_emulate_nested_eret(vcpu);
+       return 1;
+}
+
 static exit_handle_fn arm_exit_handlers[] = {
        [0 ... ESR_ELx_EC_MAX]  = kvm_handle_unknown_ec,
        [ESR_ELx_EC_WFx]        = kvm_handle_wfx,
@@ -197,6 +206,7 @@ static exit_handle_fn arm_exit_handlers[] = {
        [ESR_ELx_EC_SMC64]      = handle_smc,
        [ESR_ELx_EC_SYS64]      = kvm_handle_sys_reg,
        [ESR_ELx_EC_SVE]        = handle_sve,
+       [ESR_ELx_EC_ERET]       = kvm_handle_eret,
        [ESR_ELx_EC_IABT_LOW]   = kvm_handle_guest_abort,
        [ESR_ELx_EC_DABT_LOW]   = kvm_handle_guest_abort,
        [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
-- 
2.29.2

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