KVM: MIPS: Add Loongson-3 Virtual IPI interrupt support

This patch add Loongson-3 Virtual IPI interrupt support in the kernel.
The current implementation of IPI emulation in QEMU is based on GIC for
MIPS, but Loongson-3 doesn't use GIC. Furthermore, IPI emulation in QEMU
is too expensive for performance (because of too many context switches
between Host and Guest). With current solution, the IPI delay may even
cause RCU stall warnings in a multi-core Guest. So, we design a faster
solution that emulate IPI interrupt in kernel (only used by Loongson-3
now).

Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Co-developed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <1590220602-3547-11-git-send-email-chenhc@lemote.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index bee961997de3..c4e6b1e954f5 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -23,6 +23,8 @@
 #include <asm/inst.h>
 #include <asm/mipsregs.h>
 
+#include <kvm/iodev.h>
+
 /* MIPS KVM register ids */
 #define MIPS_CP0_32(_R, _S)					\
 	(KVM_REG_MIPS_CP0 | KVM_REG_SIZE_U32 | (8 * (_R) + (_S)))
@@ -183,11 +185,39 @@ struct kvm_vcpu_stat {
 struct kvm_arch_memory_slot {
 };
 
+#ifdef CONFIG_CPU_LOONGSON64
+struct ipi_state {
+	uint32_t status;
+	uint32_t en;
+	uint32_t set;
+	uint32_t clear;
+	uint64_t buf[4];
+};
+
+struct loongson_kvm_ipi;
+
+struct ipi_io_device {
+	int node_id;
+	struct loongson_kvm_ipi *ipi;
+	struct kvm_io_device device;
+};
+
+struct loongson_kvm_ipi {
+	spinlock_t lock;
+	struct kvm *kvm;
+	struct ipi_state ipistate[16];
+	struct ipi_io_device dev_ipi[4];
+};
+#endif
+
 struct kvm_arch {
 	/* Guest physical mm */
 	struct mm_struct gpa_mm;
 	/* Mask of CPUs needing GPA ASID flush */
 	cpumask_t asid_flush_mask;
+#ifdef CONFIG_CPU_LOONGSON64
+	struct loongson_kvm_ipi ipi;
+#endif
 };
 
 #define N_MIPS_COPROC_REGS	32
@@ -1135,6 +1165,8 @@ extern int kvm_mips_trans_mtc0(union mips_instruction inst, u32 *opc,
 /* Misc */
 extern void kvm_mips_dump_stats(struct kvm_vcpu *vcpu);
 extern unsigned long kvm_mips_get_ramsize(struct kvm *kvm);
+extern int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
+			     struct kvm_mips_interrupt *irq);
 
 static inline void kvm_arch_hardware_unsetup(void) {}
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}