KVM: arm64: nVHE: Migrate hyp interface to SMCCC

Rather than passing arbitrary function pointers to run at hyp, define
and equivalent set of SMCCC functions.

Since the SMCCC functions are strongly tied to the original function
prototypes, it is not expected for the host to ever call an invalid ID
but a warning is raised if this does ever occur.

As __kvm_vcpu_run is used for every switch between the host and a guest,
it is explicitly singled out to be identified before the other function
IDs to improve the performance of the hot path.
Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200915104643.2543892-18-ascull@google.com

arch/arm64/include/asm/kvm_asm.h

@@ -38,6 +38,30 @@
 
 #define __SMCCC_WORKAROUND_1_SMC_SZ 36
 
+#define KVM_HOST_SMCCC_ID(id)						\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
+			   ARM_SMCCC_SMC_64,				\
+			   ARM_SMCCC_OWNER_VENDOR_HYP,			\
+			   (id))
+
+#define KVM_HOST_SMCCC_FUNC(name) KVM_HOST_SMCCC_ID(__KVM_HOST_SMCCC_FUNC_##name)
+
+#define __KVM_HOST_SMCCC_FUNC___kvm_hyp_init			0
+#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run			1
+#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context		2
+#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa		3
+#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid		4
+#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_local_vmid	5
+#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff		6
+#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs			7
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_ich_vtr_el2		8
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr		9
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr		10
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs		11
+#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2		12
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs		13
+#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs		14
+
 #ifndef __ASSEMBLY__
 
 #include <linux/mm.h>

arch/arm64/include/asm/kvm_host.h

@@ -11,6 +11,7 @@
 #ifndef __ARM64_KVM_HOST_H__
 #define __ARM64_KVM_HOST_H__
 
+#include <linux/arm-smccc.h>
 #include <linux/bitmap.h>
 #include <linux/types.h>
 #include <linux/jump_label.h>
@@ -479,18 +480,20 @@ int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
-u64 __kvm_call_hyp(void *hypfn, ...);
+u64 __kvm_call_hyp_init(phys_addr_t pgd_ptr,
+			unsigned long hyp_stack_ptr,
+			unsigned long vector_ptr,
+			unsigned long tpidr_el2);
 
-#define kvm_call_hyp_nvhe(f, ...)					\
-	do {								\
-		DECLARE_KVM_NVHE_SYM(f);				\
-		__kvm_call_hyp(kvm_ksym_ref_nvhe(f), ##__VA_ARGS__);	\
-	} while(0)
-
-#define kvm_call_hyp_nvhe_ret(f, ...)					\
+#define kvm_call_hyp_nvhe(f, ...)						\
 	({								\
-		DECLARE_KVM_NVHE_SYM(f);				\
-		__kvm_call_hyp(kvm_ksym_ref_nvhe(f), ##__VA_ARGS__);	\
+		struct arm_smccc_res res;				\
+									\
+		arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(f),		\
+				  ##__VA_ARGS__, &res);			\
+		WARN_ON(res.a0 != SMCCC_RET_SUCCESS);			\
+									\
+		res.a1;							\
 	})
 
 /*
@@ -516,7 +519,7 @@ u64 __kvm_call_hyp(void *hypfn, ...);
 			ret = f(__VA_ARGS__);				\
 			isb();						\
 		} else {						\
-			ret = kvm_call_hyp_nvhe_ret(f, ##__VA_ARGS__);	\
+			ret = kvm_call_hyp_nvhe(f, ##__VA_ARGS__);	\
 		}							\
 									\
 		ret;							\

arch/arm64/kvm/arm.c

@@ -1288,7 +1288,7 @@ static void cpu_init_hyp_mode(void)
 	 * cpus_have_const_cap() wrapper.
 	 */
 	BUG_ON(!system_capabilities_finalized());
-	__kvm_call_hyp((void *)pgd_ptr, hyp_stack_ptr, vector_ptr, tpidr_el2);
+	__kvm_call_hyp_init(pgd_ptr, hyp_stack_ptr, vector_ptr, tpidr_el2);
 
 	/*
 	 * Disabling SSBD on a non-VHE system requires us to enable SSBS

arch/arm64/kvm/hyp.S

@@ -11,24 +11,12 @@
 #include <asm/cpufeature.h>
 
 /*
- * u64 __kvm_call_hyp(void *hypfn, ...);
- *
- * This is not really a variadic function in the classic C-way and care must
- * be taken when calling this to ensure parameters are passed in registers
- * only, since the stack will change between the caller and the callee.
- *
- * Call the function with the first argument containing a pointer to the
- * function you wish to call in Hyp mode, and subsequent arguments will be
- * passed as x0, x1, and x2 (a maximum of 3 arguments in addition to the
- * function pointer can be passed).  The function being called must be mapped
- * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
- * passed in x0.
- *
- * A function pointer with a value less than 0xfff has a special meaning,
- * and is used to implement hyp stubs in the same way as in
- * arch/arm64/kernel/hyp_stub.S.
+ * u64 __kvm_call_hyp_init(phys_addr_t pgd_ptr,
+ * 			   unsigned long hyp_stack_ptr,
+ * 			   unsigned long vector_ptr,
+ * 			   unsigned long tpidr_el2);
  */
-SYM_FUNC_START(__kvm_call_hyp)
+SYM_FUNC_START(__kvm_call_hyp_init)
 	hvc	#0
 	ret
-SYM_FUNC_END(__kvm_call_hyp)
+SYM_FUNC_END(__kvm_call_hyp_init)

arch/arm64/kvm/hyp/nvhe/hyp-main.c

@@ -12,25 +12,106 @@
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 
-typedef unsigned long (*hypcall_fn_t)
-	(unsigned long, unsigned long, unsigned long);
+#include <kvm/arm_hypercalls.h>
+
+static void handle_host_hcall(unsigned long func_id,
+			      struct kvm_cpu_context *host_ctxt)
+{
+	unsigned long ret = 0;
+
+	switch (func_id) {
+	case KVM_HOST_SMCCC_FUNC(__kvm_vcpu_run): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct kvm_vcpu *vcpu = (struct kvm_vcpu *)r1;
+
+		ret = __kvm_vcpu_run(vcpu);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__kvm_flush_vm_context):
+		__kvm_flush_vm_context();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_vmid_ipa): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1;
+		phys_addr_t ipa = host_ctxt->regs.regs[2];
+		int level = host_ctxt->regs.regs[3];
+
+		__kvm_tlb_flush_vmid_ipa(mmu, ipa, level);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_vmid): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1;
+
+		__kvm_tlb_flush_vmid(mmu);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_local_vmid): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1;
+
+		__kvm_tlb_flush_local_vmid(mmu);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__kvm_timer_set_cntvoff): {
+		u64 cntvoff = host_ctxt->regs.regs[1];
+
+		__kvm_timer_set_cntvoff(cntvoff);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__kvm_enable_ssbs):
+		__kvm_enable_ssbs();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_get_ich_vtr_el2):
+		ret = __vgic_v3_get_ich_vtr_el2();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_read_vmcr):
+		ret = __vgic_v3_read_vmcr();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_write_vmcr): {
+		u32 vmcr = host_ctxt->regs.regs[1];
+
+		__vgic_v3_write_vmcr(vmcr);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_init_lrs):
+		__vgic_v3_init_lrs();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__kvm_get_mdcr_el2):
+		ret = __kvm_get_mdcr_el2();
+		break;
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_save_aprs): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct vgic_v3_cpu_if *cpu_if = (struct vgic_v3_cpu_if *)r1;
+
+		__vgic_v3_save_aprs(cpu_if);
+		break;
+	}
+	case KVM_HOST_SMCCC_FUNC(__vgic_v3_restore_aprs): {
+		unsigned long r1 = host_ctxt->regs.regs[1];
+		struct vgic_v3_cpu_if *cpu_if = (struct vgic_v3_cpu_if *)r1;
+
+		__vgic_v3_restore_aprs(cpu_if);
+		break;
+	}
+	default:
+		/* Invalid host HVC. */
+		host_ctxt->regs.regs[0] = SMCCC_RET_NOT_SUPPORTED;
+		return;
+	}
+
+	host_ctxt->regs.regs[0] = SMCCC_RET_SUCCESS;
+	host_ctxt->regs.regs[1] = ret;
+}
 
 void handle_trap(struct kvm_cpu_context *host_ctxt)
 {
 	u64 esr = read_sysreg_el2(SYS_ESR);
-	hypcall_fn_t func;
-	unsigned long ret;
+	unsigned long func_id;
 
 	if (ESR_ELx_EC(esr) != ESR_ELx_EC_HVC64)
 		hyp_panic();
 
-	/*
-	 * __kvm_call_hyp takes a pointer in the host address space and
-	 * up to three arguments.
-	 */
-	func = (hypcall_fn_t)kern_hyp_va(host_ctxt->regs.regs[0]);
-	ret = func(host_ctxt->regs.regs[1],
-		   host_ctxt->regs.regs[2],
-		   host_ctxt->regs.regs[3]);
-	host_ctxt->regs.regs[0] = ret;
+	func_id = host_ctxt->regs.regs[0];
+	handle_host_hcall(func_id, host_ctxt);
 }