KVM: arm64: nv: Handle trapped ERET from virtual EL2

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>
Link: https://lore.kernel.org/r/20230209175820.1939006-12-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 206de10..d4dd949 100644 (file)
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -272,6 +272,10 @@
                (((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 bea827b..e24825d 100644 (file)
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -344,7 +344,7 @@
        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_TTA          (1 << 28)
 #define CPACR_EL1_DEFAULT      (CPACR_EL1_FPEN_EL0EN | CPACR_EL1_FPEN_EL1EN |\

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 2d8c09c..e75101f 100644 (file)
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -207,6 +207,15 @@ 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,
@@ -222,6 +231,7 @@ 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,