[PATCH v6 11/64] KVM: arm64: nv: Handle trapped ERET from virtual EL2

Marc Zyngier
2022-01-28T12:30:41Z

From: Christoffer Dall <christoffer.dall@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.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/esr.h | 4 ++++
arch/arm64/include/asm/kvm_arm.h | 2 +-
arch/arm64/kvm/handle_exit.c | 10 ++++++++++
3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index d52a0b269ee8..3574c224889f 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -257,6 +257,10 @@
(((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 0x2
+#define ESR_ELx_ERET_ISS_ERETA 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 e6e3aae87a09..5acb153a82c8 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -353,7 +353,7 @@
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 6bfb5c31cad1..2bbeed8c9786 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -171,6 +171,15 @@ 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)
+ 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,
@@ -185,6 +194,7 @@ 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,