KVM/arm64: Early PSTATE evaluation fixes

In order to be able to use promitives such as vcpu_mode_is_32bit(), we need to synchronize the guest PSTATE. However, this is currently done deep imto the bowels of the world-switch code, and we do have helpers evaluating this much earlier (__vgic_v3_perform_cpuif_access and handle_aarch32_guest, for example).

Move the saving of the guest pstate into the early fixups, which cures the first issue. The second one will be addressed separately.

Signed-off-by Marc Zyngier <[email protected]>

---
 arch/arm64/kvm/hyp/include/hyp/switch.h    | 6 ++++++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 7 ++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

arch/arm64/kvm/hyp/include/hyp/switch.h +6 -0

index 7a0af1d39303..d79fd101615f 100644
@@ -429,6 +429,12 @@ static inline bool kvm_hyp_handle_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
  */
 static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 {
+       /*
+        * Save PSTATE early so that we can evaluate the vcpu mode
+        * early on.
+        */
+       vcpu->arch.ctxt.regs.pstate = read_sysreg_el2(SYS_SPSR);
+
        if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
                vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
 

arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h +6 -2

index de7e14c862e6..7ecca8b07851 100644
@@ -70,7 +70,12 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 static inline void __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
 {
        ctxt->regs.pc                   = read_sysreg_el2(SYS_ELR);
-       ctxt->regs.pstate               = read_sysreg_el2(SYS_SPSR);
+       /*
+        * Guest PSTATE gets saved at guest fixup time in all
+        * cases. We still need to handle the nVHE host side here.
+        */
+       if (!has_vhe() && ctxt->__hyp_running_vcpu)
+               ctxt->regs.pstate       = read_sysreg_el2(SYS_SPSR);
 
        if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN))
                ctxt_sys_reg(ctxt, DISR_EL1) = read_sysreg_s(SYS_VDISR_EL2);
--

2.30.2

Protected KVM is trying to turn AArch32 exceptions into an illegal exception entry. Unfortunately, it does that it a way that is a bit

abrupt, and too early for PSTATE to be available.

Instead, move it to the fixup code, which is a more reasonable place for it. This will also be useful for the NV code.

Signed-off-by Marc Zyngier <[email protected]>

---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 8 ++++++++
 arch/arm64/kvm/hyp/nvhe/switch.c        | 8 +-------
 arch/arm64/kvm/hyp/vhe/switch.c         | 4 ++++
 3 files changed, 13 insertions(+), 7 deletions(-)

arch/arm64/kvm/hyp/include/hyp/switch.h +8 -0

index d79fd101615f..96c5f3fb7838 100644
@@ -403,6 +403,8 @@ typedef bool (*exit_handler_fn)(struct kvm_vcpu *, u64 *);
 
 static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu);
 
+static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code);
+
 /*
  * Allow the hypervisor to handle the exit with an exit handler if it has one.
  *

@@ -435,6 +437,12 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
         */
        vcpu->arch.ctxt.regs.pstate = read_sysreg_el2(SYS_SPSR);
 
+       /*
+        * Check whether we want to repaint the state one way or
+        * another.
+        */
+       early_exit_filter(vcpu, exit_code);
+
        if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
                vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
 

arch/arm64/kvm/hyp/nvhe/switch.c +1 -7

index c0e3fed26d93..d13115a12434 100644
@@ -233,7 +233,7 @@ static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu)
  * Returns false if the guest ran in AArch32 when it shouldn't have, and
  * thus should exit to the host, or true if a the guest run loop can continue.
  */
-static bool handle_aarch32_guest(struct kvm_vcpu *vcpu, u64 *exit_code)
+static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)
 {
        struct kvm *kvm = kern_hyp_va(vcpu->kvm);
 

@@ -248,10 +248,7 @@ static bool handle_aarch32_guest(struct kvm_vcpu *vcpu, u64 *exit_code)
                vcpu->arch.target = -1;
                *exit_code &= BIT(ARM_EXIT_WITH_SERROR_BIT);
                *exit_code |= ARM_EXCEPTION_IL;
-               return false;
        }
-
-       return true;
 }
 
 /* Switch to the guest for legacy non-VHE systems */

@@ -316,9 +313,6 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
                /* Jump in the fire! */
                exit_code = __guest_enter(vcpu);
 
-               if (unlikely(!handle_aarch32_guest(vcpu, &exit_code)))
-                       break;
-
                /* And we're baaack! */
        } while (fixup_guest_exit(vcpu, &exit_code));
 

arch/arm64/kvm/hyp/vhe/switch.c +4 -1

index 5a2cb5d9bc4b..fbb26b93c347 100644
@@ -112,6 +112,10 @@ static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu)
        return hyp_exit_handlers;
 }
 
+static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)
+{
+}
+
 /* Switch to the guest for VHE systems running in EL2 */
 static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
 {
--

2.30.2