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From: Bibo Mao <maobibo@loongson.cn>
To: Huacai Chen <chenhuacai@kernel.org>,
	Tianrui Zhao <zhaotianrui@loongson.cn>,
	Juergen Gross <jgross@suse.com>
Cc: loongarch@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux.dev,
	kvm@vger.kernel.org
Subject: [PATCH 5/5] LoongArch: Add pv ipi support on LoongArch system
Date: Wed,  3 Jan 2024 15:16:15 +0800
Message-Id: <20240103071615.3422264-6-maobibo@loongson.cn>
In-Reply-To: <20240103071615.3422264-1-maobibo@loongson.cn>
References: <20240103071615.3422264-1-maobibo@loongson.cn>
Precedence: bulk
MIME-Version: 1.0
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On LoongArch system, ipi hw uses iocsr registers, there is one iocsr
register access on ipi sender and two iocsr access on ipi interrupt
handler. On VM mode all iocsr registers accessing will trap into
hypervisor.

This patch adds pv ipi support for VM, hypercall instruction is used
to ipi sender, and hypervisor will inject SWI on the VM. During SWI
interrupt handler, only estat CSR register is read and written. Estat
CSR register access will not trap into hypervisor. So with pv ipi
supported, pv ipi sender will trap into hypervsor, pv ipi interrupt
handler will not trap.

Also this patch adds ipi multicast support, the method is similar with
x86. With ipi multicast support, ipi notification can be sent to at most
64 vcpus at a time. And hw cpuid is equal to logic cpuid in LoongArch
kvm hypervisor now, will add hw cpuid search logic in kvm hypervisor
in the next patch.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
 arch/loongarch/include/asm/hardirq.h   |   1 +
 arch/loongarch/include/asm/kvm_para.h  | 124 +++++++++++++++++++++++++
 arch/loongarch/include/asm/loongarch.h |   1 +
 arch/loongarch/kernel/irq.c            |   2 +-
 arch/loongarch/kernel/paravirt.c       | 103 ++++++++++++++++++++
 arch/loongarch/kernel/smp.c            |   2 +-
 arch/loongarch/kvm/exit.c              |  66 ++++++++++++-
 7 files changed, 295 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/include/asm/hardirq.h b/arch/loongarch/include/asm/hardirq.h
index 9f0038e19c7f..998011f162d0 100644
--- a/arch/loongarch/include/asm/hardirq.h
+++ b/arch/loongarch/include/asm/hardirq.h
@@ -21,6 +21,7 @@ enum ipi_msg_type {
 typedef struct {
 	unsigned int ipi_irqs[NR_IPI];
 	unsigned int __softirq_pending;
+	atomic_t messages;
 } ____cacheline_aligned irq_cpustat_t;
 
 DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
index 41200e922a82..a25a84e372b9 100644
--- a/arch/loongarch/include/asm/kvm_para.h
+++ b/arch/loongarch/include/asm/kvm_para.h
@@ -9,6 +9,10 @@
 #define HYPERVISOR_VENDOR_SHIFT		8
 #define HYPERCALL_CODE(vendor, code)	((vendor << HYPERVISOR_VENDOR_SHIFT) + code)
 
+#define KVM_HC_CODE_SERVICE		0
+#define KVM_HC_SERVICE			HYPERCALL_CODE(HYPERVISOR_KVM, KVM_HC_CODE_SERVICE)
+#define  KVM_HC_FUNC_IPI		1
+
 /*
  * LoongArch hypcall return code
  */
@@ -16,6 +20,126 @@
 #define KVM_HC_INVALID_CODE		-1UL
 #define KVM_HC_INVALID_PARAMETER	-2UL
 
+/*
+ * Hypercalls interface for KVM hypervisor
+ *
+ * a0: function identifier
+ * a1-a6: args
+ * Return value will be placed in v0.
+ * Up to 6 arguments are passed in a1, a2, a3, a4, a5, a6.
+ */
+static __always_inline long kvm_hypercall(u64 fid)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+
+	__asm__ __volatile__(
+		"hvcl "__stringify(KVM_HC_SERVICE)
+		: "=r" (ret)
+		: "r" (fun)
+		: "memory"
+		);
+
+	return ret;
+}
+
+static __always_inline long kvm_hypercall1(u64 fid, unsigned long arg0)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+	register unsigned long a1  asm("a1") = arg0;
+
+	__asm__ __volatile__(
+		"hvcl "__stringify(KVM_HC_SERVICE)
+		: "=r" (ret)
+		: "r" (fun), "r" (a1)
+		: "memory"
+		);
+
+	return ret;
+}
+
+static __always_inline long kvm_hypercall2(u64 fid,
+		unsigned long arg0, unsigned long arg1)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+	register unsigned long a1  asm("a1") = arg0;
+	register unsigned long a2  asm("a2") = arg1;
+
+	__asm__ __volatile__(
+			"hvcl "__stringify(KVM_HC_SERVICE)
+			: "=r" (ret)
+			: "r" (fun), "r" (a1), "r" (a2)
+			: "memory"
+			);
+
+	return ret;
+}
+
+static __always_inline long kvm_hypercall3(u64 fid,
+	unsigned long arg0, unsigned long arg1, unsigned long arg2)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+	register unsigned long a1  asm("a1") = arg0;
+	register unsigned long a2  asm("a2") = arg1;
+	register unsigned long a3  asm("a3") = arg2;
+
+	__asm__ __volatile__(
+		"hvcl "__stringify(KVM_HC_SERVICE)
+		: "=r" (ret)
+		: "r" (fun), "r" (a1), "r" (a2), "r" (a3)
+		: "memory"
+		);
+
+	return ret;
+}
+
+static __always_inline long kvm_hypercall4(u64 fid,
+		unsigned long arg0, unsigned long arg1, unsigned long arg2,
+		unsigned long arg3)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+	register unsigned long a1  asm("a1") = arg0;
+	register unsigned long a2  asm("a2") = arg1;
+	register unsigned long a3  asm("a3") = arg2;
+	register unsigned long a4  asm("a4") = arg3;
+
+	__asm__ __volatile__(
+		"hvcl "__stringify(KVM_HC_SERVICE)
+		: "=r" (ret)
+		: "r"(fun), "r" (a1), "r" (a2), "r" (a3), "r" (a4)
+		: "memory"
+		);
+
+	return ret;
+}
+
+static __always_inline long kvm_hypercall5(u64 fid,
+		unsigned long arg0, unsigned long arg1, unsigned long arg2,
+		unsigned long arg3, unsigned long arg4)
+{
+	register long ret asm("v0");
+	register unsigned long fun asm("a0") = fid;
+	register unsigned long a1  asm("a1") = arg0;
+	register unsigned long a2  asm("a2") = arg1;
+	register unsigned long a3  asm("a3") = arg2;
+	register unsigned long a4  asm("a4") = arg3;
+	register unsigned long a5  asm("a5") = arg4;
+
+	__asm__ __volatile__(
+		"hvcl "__stringify(KVM_HC_SERVICE)
+		: "=r" (ret)
+		: "r"(fun), "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a5)
+		: "memory"
+		);
+
+	return ret;
+}
+
+
 static inline unsigned int kvm_arch_para_features(void)
 {
 	return 0;
diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index a03b466555a1..a787b69f6fb0 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -167,6 +167,7 @@
 #define CPUCFG_KVM_SIG			CPUCFG_KVM_BASE
 #define  KVM_SIGNATURE			"KVM\0"
 #define CPUCFG_KVM_FEATURE		(CPUCFG_KVM_BASE + 4)
+#define  KVM_FEATURE_PV_IPI		BIT(1)
 #ifndef __ASSEMBLY__
 
 /* CSR */
diff --git a/arch/loongarch/kernel/irq.c b/arch/loongarch/kernel/irq.c
index 1b58f7c3eed9..b5bd298c981f 100644
--- a/arch/loongarch/kernel/irq.c
+++ b/arch/loongarch/kernel/irq.c
@@ -113,5 +113,5 @@ void __init init_IRQ(void)
 			per_cpu(irq_stack, i), per_cpu(irq_stack, i) + IRQ_STACK_SIZE);
 	}
 
-	set_csr_ecfg(ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 | ECFGF_IPI | ECFGF_PMC);
+	set_csr_ecfg(ECFGF_SIP0 | ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 | ECFGF_IPI | ECFGF_PMC);
 }
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index 21d01d05791a..a70eba278607 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/export.h>
 #include <linux/types.h>
+#include <linux/interrupt.h>
 #include <linux/jump_label.h>
 #include <linux/kvm_para.h>
 #include <asm/paravirt.h>
@@ -16,6 +17,94 @@ static u64 native_steal_clock(int cpu)
 
 DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
 
+#ifdef CONFIG_SMP
+static void pv_send_ipi_single(int cpu, unsigned int action)
+{
+	unsigned int min, old_action;
+	unsigned long ipi_bitmap = 0;
+	irq_cpustat_t *info = &per_cpu(irq_stat, cpu);
+
+	action = 1UL << action;
+	old_action = atomic_fetch_or(action, &info->messages);
+	if (old_action == 0) {
+		min = cpu_logical_map(cpu);
+		ipi_bitmap = 1;
+		kvm_hypercall2(KVM_HC_FUNC_IPI, ipi_bitmap, min);
+	}
+}
+
+static void pv_send_ipi_mask(const struct cpumask *mask, unsigned int action)
+{
+	unsigned int cpu, i, min = 0, max = 0, old_action;
+	u64 ipi_bitmap = 0;
+	irq_cpustat_t *info;
+
+	if (cpumask_empty(mask))
+		return;
+
+	action = 1UL << action;
+	for_each_cpu(i, mask) {
+		cpu = cpu_logical_map(i);
+		if (!ipi_bitmap) {
+			min = max = cpu;
+		} else if (cpu < min && (max - cpu) < BITS_PER_LONG) {
+			ipi_bitmap <<= min - cpu;
+			min = cpu;
+		} else if (cpu > min && cpu < min + BITS_PER_LONG) {
+			max = cpu < max ? max : cpu;
+		} else {
+			kvm_hypercall2(KVM_HC_FUNC_IPI, ipi_bitmap, min);
+			min = max = cpu;
+			ipi_bitmap = 0;
+		}
+		info = &per_cpu(irq_stat, i);
+		old_action = atomic_fetch_or(action, &info->messages);
+		if (old_action == 0)
+			__set_bit(cpu - min, (unsigned long *)&ipi_bitmap);
+	}
+
+	if (ipi_bitmap)
+		kvm_hypercall2(KVM_HC_FUNC_IPI, ipi_bitmap, min);
+}
+
+static irqreturn_t loongson_do_swi(int irq, void *dev)
+{
+	irq_cpustat_t *info;
+	long action;
+
+	clear_csr_estat(1 << INT_SWI0);
+
+	info = this_cpu_ptr(&irq_stat);
+	do {
+		action = atomic_xchg(&info->messages, 0);
+		if (action & SMP_CALL_FUNCTION) {
+			generic_smp_call_function_interrupt();
+			info->ipi_irqs[IPI_CALL_FUNCTION]++;
+		}
+
+		if (action & SMP_RESCHEDULE) {
+			scheduler_ipi();
+			info->ipi_irqs[IPI_RESCHEDULE]++;
+		}
+	} while (action);
+
+	return IRQ_HANDLED;
+}
+
+static void pv_ipi_init(void)
+{
+	int r, swi0;
+
+	swi0 = get_percpu_irq(INT_SWI0);
+	if (swi0 < 0)
+		panic("SIP0 IRQ mapping failed\n");
+	irq_set_percpu_devid(swi0);
+	r = request_percpu_irq(swi0, loongson_do_swi, "SWI0", &irq_stat);
+	if (r < 0)
+		panic("SIP0 IRQ request failed\n");
+}
+#endif
+
 static bool kvm_para_available(void)
 {
 	static int hypervisor_type;
@@ -32,10 +121,24 @@ static bool kvm_para_available(void)
 
 int __init pv_guest_init(void)
 {
+	int feature;
+
 	if (!cpu_has_hypervisor)
 		return 0;
 	if (!kvm_para_available())
 		return 0;
 
+	/*
+	 * check whether KVM hypervisor supports pv_ipi or not
+	 */
+#ifdef CONFIG_SMP
+	feature = read_cpucfg(CPUCFG_KVM_FEATURE);
+	if (feature & KVM_FEATURE_PV_IPI) {
+		smp_ops.call_func_single_ipi	= pv_send_ipi_single;
+		smp_ops.call_func_ipi		= pv_send_ipi_mask;
+		smp_ops.ipi_init		= pv_ipi_init;
+	}
+#endif
+
 	return 1;
 }
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 8cce7839b22f..ebcf2ac8a9c2 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -283,7 +283,7 @@ void loongson_boot_secondary(int cpu, struct task_struct *idle)
 void loongson_init_secondary(void)
 {
 	unsigned int cpu = smp_processor_id();
-	unsigned int imask = ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 |
+	unsigned int imask = ECFGF_SIP0 | ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 |
 			     ECFGF_IPI | ECFGF_PMC | ECFGF_TIMER;
 
 	change_csr_ecfg(ECFG0_IM, imask);
diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index e233d7b3b76d..bd8a631d8626 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -227,6 +227,9 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
 	case CPUCFG_KVM_SIG:
 		vcpu->arch.gprs[rd] = *(unsigned int *)KVM_SIGNATURE;
 		break;
+	case CPUCFG_KVM_FEATURE:
+		vcpu->arch.gprs[rd] = KVM_FEATURE_PV_IPI;
+		break;
 	default:
 		vcpu->arch.gprs[rd] = 0;
 		break;
@@ -664,12 +667,71 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu)
 	return RESUME_GUEST;
 }
 
+static int kvm_pv_send_ipi(struct kvm_vcpu *vcpu, int sgi)
+{
+	int ret = 0;
+	u64 ipi_bitmap;
+	unsigned int min, cpu;
+	struct kvm_vcpu *dest;
+
+	ipi_bitmap = vcpu->arch.gprs[LOONGARCH_GPR_A1];
+	min = vcpu->arch.gprs[LOONGARCH_GPR_A2];
+
+	if (ipi_bitmap) {
+		cpu = find_first_bit((void *)&ipi_bitmap, BITS_PER_LONG);
+		while (cpu < BITS_PER_LONG) {
+			if ((cpu + min) < KVM_MAX_VCPUS) {
+				dest = kvm_get_vcpu_by_id(vcpu->kvm, cpu + min);
+				kvm_queue_irq(dest, sgi);
+				kvm_vcpu_kick(dest);
+			}
+			cpu = find_next_bit((void *)&ipi_bitmap, BITS_PER_LONG, cpu + 1);
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * hypcall emulation always return to guest, Caller should check retval.
+ */
+static void kvm_handle_pv_hcall(struct kvm_vcpu *vcpu)
+{
+	unsigned long func = vcpu->arch.gprs[LOONGARCH_GPR_A0];
+	long ret;
+
+	switch (func) {
+	case KVM_HC_FUNC_IPI:
+		kvm_pv_send_ipi(vcpu, INT_SWI0);
+		ret = KVM_HC_STATUS_SUCCESS;
+		break;
+	default:
+		ret = KVM_HC_INVALID_CODE;
+		break;
+	};
+
+	vcpu->arch.gprs[LOONGARCH_GPR_A0] = ret;
+}
+
 static int kvm_handle_hypcall(struct kvm_vcpu *vcpu)
 {
+	larch_inst inst;
+	unsigned int code;
+
+	inst.word = vcpu->arch.badi;
+	code = inst.reg0i15_format.immediate;
 	update_pc(&vcpu->arch);
 
-	/* Treat it as noop intruction, only set return value */
-	vcpu->arch.gprs[LOONGARCH_GPR_A0] = KVM_HC_INVALID_CODE;
+	switch (code) {
+	case KVM_HC_SERVICE:
+		kvm_handle_pv_hcall(vcpu);
+		break;
+	default:
+		/* Treat it as noop intruction, only set return value */
+		vcpu->arch.gprs[LOONGARCH_GPR_A0] = KVM_HC_INVALID_CODE;
+		break;
+	}
+
 	return RESUME_GUEST;
 }
 
-- 
2.39.3