[PATCH v3 04/12] KVM: arm64: nVHE: Remove __guest_exit_panic path

[Pierre-Clément Tosi]

In invalid_host_el2_vect (i.e. EL2{t,h} handlers in nVHE guest context),
remove the duplicate vCPU context check that __guest_exit_panic also
performs, allowing an unconditional branch to it.

Rename __guest_exit_panic to __hyp_panic to better reflect that it might
not exit through the guest but will always (directly or indirectly) end
up executing hyp_panic(). Fix its wrong (probably bitrotten) ABI doc to
reflect the ABI expected by VHE and (now) nVHE.

Use CPU_LR_OFFSET to clarify that the routine returns to hyp_panic().

Restore x0, x1 before calling hyp_panic when __hyp_panic is executed in
host context (i.e. called from __kvm_hyp_vector).

Signed-off-by: Pierre-Clément Tosi <ptosi at google.com>
---
 arch/arm64/kvm/hyp/entry.S              | 14 +++++++++-----
 arch/arm64/kvm/hyp/hyp-entry.S          |  2 +-
 arch/arm64/kvm/hyp/include/hyp/switch.h |  4 ++--
 arch/arm64/kvm/hyp/nvhe/host.S          |  8 +-------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index bcaaf1a11b4e..6a1ce9d21e5b 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -83,7 +83,7 @@ alternative_else_nop_endif
 	eret
 	sb
 
-SYM_INNER_LABEL(__guest_exit_restore_elr_and_panic, SYM_L_GLOBAL)
+SYM_INNER_LABEL(__hyp_restore_elr_and_panic, SYM_L_GLOBAL)
 	// x0-x29,lr: hyp regs
 
 	stp	x0, x1, [sp, #-16]!
@@ -92,13 +92,15 @@ SYM_INNER_LABEL(__guest_exit_restore_elr_and_panic, SYM_L_GLOBAL)
 	msr	elr_el2, x0
 	ldp	x0, x1, [sp], #16
 
-SYM_INNER_LABEL(__guest_exit_panic, SYM_L_GLOBAL)
-	// x2-x29,lr: vcpu regs
-	// vcpu x0-x1 on the stack
+SYM_INNER_LABEL(__hyp_panic, SYM_L_GLOBAL)
+	// x0-x29,lr: vcpu regs
+
+	stp	x0, x1, [sp, #-16]!
 
 	// If the hyp context is loaded, go straight to hyp_panic
 	get_loaded_vcpu x0, x1
 	cbnz	x0, 1f
+	ldp	x0, x1, [sp], #16
 	b	hyp_panic
 
 1:
@@ -110,10 +112,12 @@ SYM_INNER_LABEL(__guest_exit_panic, SYM_L_GLOBAL)
 	// accurate if the guest had been completely restored.
 	adr_this_cpu x0, kvm_hyp_ctxt, x1
 	adr_l	x1, hyp_panic
-	str	x1, [x0, #CPU_XREG_OFFSET(30)]
+	str	x1, [x0, #CPU_LR_OFFSET]
 
 	get_vcpu_ptr	x1, x0
 
+	// Keep x0-x1 on the stack for __guest_exit
+
 SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL)
 	// x0: return code
 	// x1: vcpu
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 03f97d71984c..7e65ef738ec9 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -122,7 +122,7 @@ el2_error:
 	eret
 	sb
 
-.macro invalid_vector	label, target = __guest_exit_panic
+.macro invalid_vector	label, target = __hyp_panic
 	.align	2
 SYM_CODE_START_LOCAL(\label)
 	b \target
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 19a7ca2c1277..9387e3a0b680 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -753,7 +753,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
 
 static inline void __kvm_unexpected_el2_exception(void)
 {
-	extern char __guest_exit_restore_elr_and_panic[];
+	extern char __hyp_restore_elr_and_panic[];
 	unsigned long addr, fixup;
 	struct kvm_exception_table_entry *entry, *end;
 	unsigned long elr_el2 = read_sysreg(elr_el2);
@@ -776,7 +776,7 @@ static inline void __kvm_unexpected_el2_exception(void)
 
 	/* Trigger a panic after restoring the hyp context. */
 	this_cpu_ptr(&kvm_hyp_ctxt)->sys_regs[ELR_EL2] = elr_el2;
-	write_sysreg(__guest_exit_restore_elr_and_panic, elr_el2);
+	write_sysreg(__hyp_restore_elr_and_panic, elr_el2);
 }
 
 #endif /* __ARM64_KVM_HYP_SWITCH_H__ */
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 135cfb294ee5..7397b4f1838a 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -196,19 +196,13 @@ SYM_FUNC_END(__host_hvc)
 	tbz	x0, #PAGE_SHIFT, .L__hyp_sp_overflow\@
 	sub	x0, sp, x0			// x0'' = sp' - x0' = (sp + x0) - sp = x0
 	sub	sp, sp, x0			// sp'' = sp' - x0 = (sp + x0) - x0 = sp
-
 	/* If a guest is loaded, panic out of it. */
-	stp	x0, x1, [sp, #-16]!
-	get_loaded_vcpu x0, x1
-	cbnz	x0, __guest_exit_panic
-	add	sp, sp, #16
-
 	/*
 	 * The panic may not be clean if the exception is taken before the host
 	 * context has been saved by __host_exit or after the hyp context has
 	 * been partially clobbered by __host_enter.
 	 */
-	b	hyp_panic
+	b	__hyp_panic
 
 .L__hyp_sp_overflow\@:
 	/* Switch to the overflow stack */
-- 
2.45.0.118.g7fe29c98d7-goog