Subject: [PATCH v2 11/94] KVM: arm64: nv: Handle trapped ERET from virtual EL2

From: Marc Zyngier <[email-masked]>
Date: Tue, 11 Feb 2020 17:48:15 +0000

From: Christoffer Dall <[email-masked]>

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 <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 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 cb29253ae86b..b15921dc889a 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -249,6 +249,11 @@
 		(((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 93469ac81fef..084844ec0b06 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -322,7 +322,7 @@
 	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 be5acf72c81e..c3398e6ebbbe 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -210,6 +210,15 @@ static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	return 1;
 }
 
+static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_ERET_ISS_ERET_ERETAx)
+		return kvm_handle_ptrauth(vcpu, run);
+
+	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,
@@ -224,6 +233,7 @@ 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,
-- 
2.20.1

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