KVM: arm64: nVHE: Use separate vector for the host

The host is treated differently from the guests when an exception is
taken so introduce a separate vector that is specialized for the host.
This also allows the nVHE specific code to move out of hyp-entry.S and
into nvhe/host.S.

The host is only expected to make HVC calls and anything else is
considered invalid and results in a panic.

Hyp initialization is now passed the vector that is used for the host
and it is swapped for the guest vector during the context switch.

Signed-off-by: Andrew Scull <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm64/include/asm/kvm_asm.h

···
 struct kvm_s2_mmu;
 
 DECLARE_KVM_NVHE_SYM(__kvm_hyp_init);
+DECLARE_KVM_NVHE_SYM(__kvm_hyp_host_vector);
 DECLARE_KVM_HYP_SYM(__kvm_hyp_vector);
 #define __kvm_hyp_init		CHOOSE_NVHE_SYM(__kvm_hyp_init)
+#define __kvm_hyp_host_vector	CHOOSE_NVHE_SYM(__kvm_hyp_host_vector)
 #define __kvm_hyp_vector	CHOOSE_HYP_SYM(__kvm_hyp_vector)
 
 #ifdef CONFIG_KVM_INDIRECT_VECTORS

arch/arm64/kernel/image-vars.h

···
 /* Global kernel state accessed by nVHE hyp code. */
 KVM_NVHE_ALIAS(arm64_ssbd_callback_required);
 KVM_NVHE_ALIAS(kvm_host_data);
+KVM_NVHE_ALIAS(kvm_hyp_vector);
 KVM_NVHE_ALIAS(kvm_vgic_global_state);
 
 /* Kernel constant needed to compute idmap addresses. */

arch/arm64/kvm/arm.c

···
 
 	pgd_ptr = kvm_mmu_get_httbr();
 	hyp_stack_ptr = __this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE;
-	vector_ptr = __this_cpu_read(kvm_hyp_vector);
+	vector_ptr = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector));
 
 	/*
 	 * Call initialization code, and switch to the full blown HYP code.
···
 
 	for_each_possible_cpu(cpu) {
 		struct kvm_host_data *cpu_data;
+		unsigned long *vector;
 
 		cpu_data = per_cpu_ptr(&kvm_host_data, cpu);
 		err = create_hyp_mappings(cpu_data, cpu_data + 1, PAGE_HYP);
 
 		if (err) {
 			kvm_err("Cannot map host CPU state: %d\n", err);
+			goto out_err;
+		}
+
+		vector = per_cpu_ptr(&kvm_hyp_vector, cpu);
+		err = create_hyp_mappings(vector, vector + 1, PAGE_HYP);
+
+		if (err) {
+			kvm_err("Cannot map hyp guest vector address\n");
 			goto out_err;
 		}
 	}

arch/arm64/kvm/hyp/hyp-entry.S

···
 #include <asm/cpufeature.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
-#include <asm/kvm_mmu.h>
 #include <asm/mmu.h>
 
 .macro save_caller_saved_regs_vect
···
 
 	.text
 
-.macro do_el2_call
-	/*
-	 * Shuffle the parameters before calling the function
-	 * pointed to in x0. Assumes parameters in x[1,2,3].
-	 */
-	str	lr, [sp, #-16]!
-	mov	lr, x0
-	mov	x0, x1
-	mov	x1, x2
-	mov	x2, x3
-	blr	lr
-	ldr	lr, [sp], #16
-.endm
-
 el1_sync:				// Guest trapped into EL2
 
 	mrs	x0, esr_el2
···
 	ccmp	x0, #ESR_ELx_EC_HVC32, #4, ne
 	b.ne	el1_trap
 
-#ifdef __KVM_NVHE_HYPERVISOR__
-	mrs	x1, vttbr_el2		// If vttbr is valid, the guest
-	cbnz	x1, el1_hvc_guest	// called HVC
-
-	/* Here, we're pretty sure the host called HVC. */
-	ldp	x0, x1, [sp], #16
-
-	/* Check for a stub HVC call */
-	cmp	x0, #HVC_STUB_HCALL_NR
-	b.hs	1f
-
-	/*
-	 * Compute the idmap address of __kvm_handle_stub_hvc and
-	 * jump there. Since we use kimage_voffset, do not use the
-	 * HYP VA for __kvm_handle_stub_hvc, but the kernel VA instead
-	 * (by loading it from the constant pool).
-	 *
-	 * Preserve x0-x4, which may contain stub parameters.
-	 */
-	ldr	x5, =__kvm_handle_stub_hvc
-	ldr_l	x6, kimage_voffset
-
-	/* x5 = __pa(x5) */
-	sub	x5, x5, x6
-	br	x5
-
-1:
-	/*
-	 * Perform the EL2 call
-	 */
-	kern_hyp_va	x0
-	do_el2_call
-
-	eret
-	sb
-#endif /* __KVM_NVHE_HYPERVISOR__ */
-
-el1_hvc_guest:
 	/*
 	 * Fastest possible path for ARM_SMCCC_ARCH_WORKAROUND_1.
 	 * The workaround has already been applied on the host,
···
 	eret
 	sb
 
-#ifdef __KVM_NVHE_HYPERVISOR__
-SYM_FUNC_START(__hyp_do_panic)
-	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
-		      PSR_MODE_EL1h)
-	msr	spsr_el2, lr
-	ldr	lr, =panic
-	msr	elr_el2, lr
-	eret
-	sb
-SYM_FUNC_END(__hyp_do_panic)
-#endif
-
 .macro invalid_vector	label, target = hyp_panic
 	.align	2
 SYM_CODE_START(\label)
···
 	invalid_vector	el2t_irq_invalid
 	invalid_vector	el2t_fiq_invalid
 	invalid_vector	el2t_error_invalid
-	invalid_vector	el2h_sync_invalid
 	invalid_vector	el2h_irq_invalid
 	invalid_vector	el2h_fiq_invalid
 	invalid_vector	el1_fiq_invalid

arch/arm64/kvm/hyp/nvhe/Makefile

···
 asflags-y := -D__KVM_NVHE_HYPERVISOR__
 ccflags-y := -D__KVM_NVHE_HYPERVISOR__
 
-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o
+obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o
 

arch/arm64/kvm/hyp/nvhe/host.S

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 - Google Inc
+ * Author: Andrew Scull <[e-mail]>
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/assembler.h>
+#include <asm/kvm_asm.h>
+#include <asm/kvm_mmu.h>
+
+	.text
+
+SYM_FUNC_START(__hyp_do_panic)
+	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
+		      PSR_MODE_EL1h)
+	msr	spsr_el2, lr
+	ldr	lr, =panic
+	msr	elr_el2, lr
+	eret
+	sb
+SYM_FUNC_END(__hyp_do_panic)
+
+.macro host_el1_sync_vect
+	.align 7
+.L__vect_start\@:
+	esb
+	stp	x0, x1, [sp, #-16]!
+	mrs	x0, esr_el2
+	lsr	x0, x0, #ESR_ELx_EC_SHIFT
+	cmp	x0, #ESR_ELx_EC_HVC64
+	ldp	x0, x1, [sp], #16
+	b.ne	hyp_panic
+
+	/* Check for a stub HVC call */
+	cmp	x0, #HVC_STUB_HCALL_NR
+	b.hs	1f
+
+	/*
+	 * Compute the idmap address of __kvm_handle_stub_hvc and
+	 * jump there. Since we use kimage_voffset, do not use the
+	 * HYP VA for __kvm_handle_stub_hvc, but the kernel VA instead
+	 * (by loading it from the constant pool).
+	 *
+	 * Preserve x0-x4, which may contain stub parameters.
+	 */
+	ldr	x5, =__kvm_handle_stub_hvc
+	ldr_l	x6, kimage_voffset
+
+	/* x5 = __pa(x5) */
+	sub	x5, x5, x6
+	br	x5
+
+1:
+	/*
+	 * Shuffle the parameters before calling the function
+	 * pointed to in x0. Assumes parameters in x[1,2,3].
+	 */
+	kern_hyp_va	x0
+	str	lr, [sp, #-16]!
+	mov	lr, x0
+	mov	x0, x1
+	mov	x1, x2
+	mov	x2, x3
+	blr	lr
+	ldr	lr, [sp], #16
+
+	eret
+	sb
+.L__vect_end\@:
+.if ((.L__vect_end\@ - .L__vect_start\@) > 0x80)
+	.error "host_el1_sync_vect larger than vector entry"
+.endif
+.endm
+
+.macro invalid_host_vect
+	.align 7
+	b	hyp_panic
+.endm
+
+/*
+ * CONFIG_KVM_INDIRECT_VECTORS is not applied to the host vectors because the
+ * host knows about the EL2 vectors already, and there is no point in hiding
+ * them.
+ */
+	.align 11
+SYM_CODE_START(__kvm_hyp_host_vector)
+	invalid_host_vect			// Synchronous EL2t
+	invalid_host_vect			// IRQ EL2t
+	invalid_host_vect			// FIQ EL2t
+	invalid_host_vect			// Error EL2t
+
+	invalid_host_vect			// Synchronous EL2h
+	invalid_host_vect			// IRQ EL2h
+	invalid_host_vect			// FIQ EL2h
+	invalid_host_vect			// Error EL2h
+
+	host_el1_sync_vect			// Synchronous 64-bit EL1
+	invalid_host_vect			// IRQ 64-bit EL1
+	invalid_host_vect			// FIQ 64-bit EL1
+	invalid_host_vect			// Error 64-bit EL1
+
+	invalid_host_vect			// Synchronous 32-bit EL1
+	invalid_host_vect			// IRQ 32-bit EL1
+	invalid_host_vect			// FIQ 32-bit EL1
+	invalid_host_vect			// Error 32-bit EL1
+SYM_CODE_END(__kvm_hyp_host_vector)

arch/arm64/kvm/hyp/nvhe/switch.c

···
 	}
 
 	write_sysreg(val, cptr_el2);
+	write_sysreg(__hyp_this_cpu_read(kvm_hyp_vector), vbar_el2);
 
 	if (cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT)) {
 		struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
···
 
 static void __deactivate_traps(struct kvm_vcpu *vcpu)
 {
+	extern char __kvm_hyp_host_vector[];
 	u64 mdcr_el2;
 
 	___deactivate_traps(vcpu);
···
 	write_sysreg(mdcr_el2, mdcr_el2);
 	write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2);
 	write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
+	write_sysreg(__kvm_hyp_host_vector, vbar_el2);
 }
 
 static void __load_host_stage2(void)