LoongArch: KVM: Supplement kvm document about LoongArch-specific part

Supplement kvm document about LoongArch-specific part, such as add
api introduction for GET/SET_ONE_REG, GET/SET_FPU, GET/SET_MP_STATE,
etc.
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Documentation/virt/kvm/api.rst

@@ -416,6 +416,13 @@ Reads the general purpose registers from the vcpu.
 	__u64 pc;
   };
 
+  /* LoongArch */
+  struct kvm_regs {
+	/* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
+	unsigned long gpr[32];
+	unsigned long pc;
+  };
+
 
 4.12 KVM_SET_REGS
 -----------------
@@ -506,7 +513,7 @@ translation mode.
 ------------------
 
 :Capability: basic
-:Architectures: x86, ppc, mips, riscv
+:Architectures: x86, ppc, mips, riscv, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_interrupt (in)
 :Returns: 0 on success, negative on failure.
@@ -592,6 +599,14 @@ b) KVM_INTERRUPT_UNSET
 
 This is an asynchronous vcpu ioctl and can be invoked from any thread.
 
+LOONGARCH:
+^^^^^^^^^^
+
+Queues an external interrupt to be injected into the virtual CPU. A negative
+interrupt number dequeues the interrupt.
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
 
 4.17 KVM_DEBUG_GUEST
 --------------------
@@ -737,7 +752,7 @@ signal mask.
 ----------------
 
 :Capability: basic
-:Architectures: x86
+:Architectures: x86, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_fpu (out)
 :Returns: 0 on success, -1 on error
@@ -746,7 +761,7 @@ Reads the floating point state from the vcpu.
 
 ::
 
-  /* for KVM_GET_FPU and KVM_SET_FPU */
+  /* x86: for KVM_GET_FPU and KVM_SET_FPU */
   struct kvm_fpu {
 	__u8  fpr[8][16];
 	__u16 fcw;
@@ -761,12 +776,21 @@ Reads the floating point state from the vcpu.
 	__u32 pad2;
   };
 
+  /* LoongArch: for KVM_GET_FPU and KVM_SET_FPU */
+  struct kvm_fpu {
+	__u32 fcsr;
+	__u64 fcc;
+	struct kvm_fpureg {
+		__u64 val64[4];
+	}fpr[32];
+  };
+
 
 4.23 KVM_SET_FPU
 ----------------
 
 :Capability: basic
-:Architectures: x86
+:Architectures: x86, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_fpu (in)
 :Returns: 0 on success, -1 on error
@@ -775,7 +799,7 @@ Writes the floating point state to the vcpu.
 
 ::
 
-  /* for KVM_GET_FPU and KVM_SET_FPU */
+  /* x86: for KVM_GET_FPU and KVM_SET_FPU */
   struct kvm_fpu {
 	__u8  fpr[8][16];
 	__u16 fcw;
@@ -790,6 +814,15 @@ Writes the floating point state to the vcpu.
 	__u32 pad2;
   };
 
+  /* LoongArch: for KVM_GET_FPU and KVM_SET_FPU */
+  struct kvm_fpu {
+	__u32 fcsr;
+	__u64 fcc;
+	struct kvm_fpureg {
+		__u64 val64[4];
+	}fpr[32];
+  };
+
 
 4.24 KVM_CREATE_IRQCHIP
 -----------------------
@@ -1387,7 +1420,7 @@ documentation when it pops into existence).
 -------------------
 
 :Capability: KVM_CAP_ENABLE_CAP
-:Architectures: mips, ppc, s390, x86
+:Architectures: mips, ppc, s390, x86, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_enable_cap (in)
 :Returns: 0 on success; -1 on error
@@ -1442,7 +1475,7 @@ for vm-wide capabilities.
 ---------------------
 
 :Capability: KVM_CAP_MP_STATE
-:Architectures: x86, s390, arm64, riscv
+:Architectures: x86, s390, arm64, riscv, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_mp_state (out)
 :Returns: 0 on success; -1 on error
@@ -1460,7 +1493,7 @@ Possible values are:
 
    ==========================    ===============================================
    KVM_MP_STATE_RUNNABLE         the vcpu is currently running
-                                 [x86,arm64,riscv]
+                                 [x86,arm64,riscv,loongarch]
    KVM_MP_STATE_UNINITIALIZED    the vcpu is an application processor (AP)
                                  which has not yet received an INIT signal [x86]
    KVM_MP_STATE_INIT_RECEIVED    the vcpu has received an INIT signal, and is
@@ -1516,11 +1549,14 @@ For riscv:
 The only states that are valid are KVM_MP_STATE_STOPPED and
 KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
 
+On LoongArch, only the KVM_MP_STATE_RUNNABLE state is used to reflect
+whether the vcpu is runnable.
+
 4.39 KVM_SET_MP_STATE
 ---------------------
 
 :Capability: KVM_CAP_MP_STATE
-:Architectures: x86, s390, arm64, riscv
+:Architectures: x86, s390, arm64, riscv, loongarch
 :Type: vcpu ioctl
 :Parameters: struct kvm_mp_state (in)
 :Returns: 0 on success; -1 on error
@@ -1538,6 +1574,9 @@ For arm64/riscv:
 The only states that are valid are KVM_MP_STATE_STOPPED and
 KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
 
+On LoongArch, only the KVM_MP_STATE_RUNNABLE state is used to reflect
+whether the vcpu is runnable.
+
 4.40 KVM_SET_IDENTITY_MAP_ADDR
 ------------------------------
 
@@ -2841,6 +2880,19 @@ Following are the RISC-V D-extension registers:
   0x8020 0000 0600 0020 fcsr      Floating point control and status register
 ======================= ========= =============================================
 
+LoongArch registers are mapped using the lower 32 bits. The upper 16 bits of
+that is the register group type.
+
+LoongArch csr registers are used to control guest cpu or get status of guest
+cpu, and they have the following id bit patterns::
+
+  0x9030 0000 0001 00 <reg:5> <sel:3>   (64-bit)
+
+LoongArch KVM control registers are used to implement some new defined functions
+such as set vcpu counter or reset vcpu, and they have the following id bit patterns::
+
+  0x9030 0000 0002 <reg:16>
+
 
 4.69 KVM_GET_ONE_REG
 --------------------