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Subject[PATCH v10 18/19] RISC-V: KVM: Document RISC-V specific parts of KVM API.
Date
Document RISC-V specific parts of the KVM API, such as:
- The interrupt numbers passed to the KVM_INTERRUPT ioctl.
- The states supported by the KVM_{GET,SET}_MP_STATE ioctls.
- The registers supported by the KVM_{GET,SET}_ONE_REG interface
and the encoding of those register ids.
- The exit reason KVM_EXIT_RISCV_SBI for SBI calls forwarded to
userspace tool.

CC: Jonathan Corbet <corbet@lwn.net>
CC: linux-doc@vger.kernel.org
Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
Documentation/virt/kvm/api.txt | 169 +++++++++++++++++++++++++++++++--
1 file changed, 162 insertions(+), 7 deletions(-)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index ebb37b34dcfc..381a2e6df8c6 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -471,7 +471,7 @@ struct kvm_translation {
4.16 KVM_INTERRUPT

Capability: basic
-Architectures: x86, ppc, mips
+Architectures: x86, ppc, mips, riscv
Type: vcpu ioctl
Parameters: struct kvm_interrupt (in)
Returns: 0 on success, negative on failure.
@@ -531,6 +531,22 @@ interrupt number dequeues the interrupt.

This is an asynchronous vcpu ioctl and can be invoked from any thread.

+RISC-V:
+
+Queues an external interrupt to be injected into the virutal CPU. This ioctl
+is overloaded with 2 different irq values:
+
+a) KVM_INTERRUPT_SET
+
+ This sets external interrupt for a virtual CPU and it will receive
+ once it is ready.
+
+b) KVM_INTERRUPT_UNSET
+
+ This clears pending external interrupt for a virtual CPU.
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+

4.17 KVM_DEBUG_GUEST

@@ -1239,7 +1255,7 @@ for vm-wide capabilities.
4.38 KVM_GET_MP_STATE

Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
+Architectures: x86, s390, arm, arm64, riscv
Type: vcpu ioctl
Parameters: struct kvm_mp_state (out)
Returns: 0 on success; -1 on error
@@ -1253,7 +1269,8 @@ uniprocessor guests).

Possible values are:

- - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64]
+ - KVM_MP_STATE_RUNNABLE: the vcpu is currently running
+ [x86,arm/arm64,riscv]
- 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
@@ -1262,7 +1279,7 @@ Possible values are:
is waiting for an interrupt [x86]
- KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
accessible via KVM_GET_VCPU_EVENTS) [x86]
- - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
+ - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64,riscv]
- KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390]
- KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted)
[s390]
@@ -1273,7 +1290,7 @@ On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
in-kernel irqchip, the multiprocessing state must be maintained by userspace on
these architectures.

-For arm/arm64:
+For arm/arm64/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.
@@ -1281,7 +1298,7 @@ KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
4.39 KVM_SET_MP_STATE

Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
+Architectures: x86, s390, arm, arm64, riscv
Type: vcpu ioctl
Parameters: struct kvm_mp_state (in)
Returns: 0 on success; -1 on error
@@ -1293,7 +1310,7 @@ On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
in-kernel irqchip, the multiprocessing state must be maintained by userspace on
these architectures.

-For arm/arm64:
+For arm/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.
@@ -2302,6 +2319,127 @@ following id bit patterns:
0x7020 0000 0003 02 <0:3> <reg:5>


+RISC-V registers are mapped using the lower 32 bits. The upper 8 bits of
+that is the register group type.
+
+RISC-V config registers are meant for configuring a Guest VCPU and it has
+the following id bit patterns:
+ 0x8020 0000 01 <index into the kvm_riscv_config struct:24> (32bit Host)
+ 0x8030 0000 01 <index into the kvm_riscv_config struct:24> (64bit Host)
+
+Following are the RISC-V config registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x80x0 0000 0100 0000 isa ISA feature bitmap of Guest VCPU
+
+The isa config register can be read anytime but can only be written before
+a Guest VCPU runs. It will have ISA feature bits matching underlying host
+set by default.
+
+RISC-V core registers represent the general excution state of a Guest VCPU
+and it has the following id bit patterns:
+ 0x8020 0000 02 <index into the kvm_riscv_core struct:24> (32bit Host)
+ 0x8030 0000 02 <index into the kvm_riscv_core struct:24> (64bit Host)
+
+Following are the RISC-V core registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x80x0 0000 0200 0000 regs.pc Program counter
+ 0x80x0 0000 0200 0001 regs.ra Return address
+ 0x80x0 0000 0200 0002 regs.sp Stack pointer
+ 0x80x0 0000 0200 0003 regs.gp Global pointer
+ 0x80x0 0000 0200 0004 regs.tp Task pointer
+ 0x80x0 0000 0200 0005 regs.t0 Caller saved register 0
+ 0x80x0 0000 0200 0006 regs.t1 Caller saved register 1
+ 0x80x0 0000 0200 0007 regs.t2 Caller saved register 2
+ 0x80x0 0000 0200 0008 regs.s0 Callee saved register 0
+ 0x80x0 0000 0200 0009 regs.s1 Callee saved register 1
+ 0x80x0 0000 0200 000a regs.a0 Function argument (or return value) 0
+ 0x80x0 0000 0200 000b regs.a1 Function argument (or return value) 1
+ 0x80x0 0000 0200 000c regs.a2 Function argument 2
+ 0x80x0 0000 0200 000d regs.a3 Function argument 3
+ 0x80x0 0000 0200 000e regs.a4 Function argument 4
+ 0x80x0 0000 0200 000f regs.a5 Function argument 5
+ 0x80x0 0000 0200 0010 regs.a6 Function argument 6
+ 0x80x0 0000 0200 0011 regs.a7 Function argument 7
+ 0x80x0 0000 0200 0012 regs.s2 Callee saved register 2
+ 0x80x0 0000 0200 0013 regs.s3 Callee saved register 3
+ 0x80x0 0000 0200 0014 regs.s4 Callee saved register 4
+ 0x80x0 0000 0200 0015 regs.s5 Callee saved register 5
+ 0x80x0 0000 0200 0016 regs.s6 Callee saved register 6
+ 0x80x0 0000 0200 0017 regs.s7 Callee saved register 7
+ 0x80x0 0000 0200 0018 regs.s8 Callee saved register 8
+ 0x80x0 0000 0200 0019 regs.s9 Callee saved register 9
+ 0x80x0 0000 0200 001a regs.s10 Callee saved register 10
+ 0x80x0 0000 0200 001b regs.s11 Callee saved register 11
+ 0x80x0 0000 0200 001c regs.t3 Caller saved register 3
+ 0x80x0 0000 0200 001d regs.t4 Caller saved register 4
+ 0x80x0 0000 0200 001e regs.t5 Caller saved register 5
+ 0x80x0 0000 0200 001f regs.t6 Caller saved register 6
+ 0x80x0 0000 0200 0020 mode Privilege mode (1 = S-mode or 0 = U-mode)
+
+RISC-V csr registers represent the supervisor mode control/status registers
+of a Guest VCPU and it has the following id bit patterns:
+ 0x8020 0000 03 <index into the kvm_riscv_csr struct:24> (32bit Host)
+ 0x8030 0000 03 <index into the kvm_riscv_csr struct:24> (64bit Host)
+
+Following are the RISC-V csr registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x80x0 0000 0300 0000 sstatus Supervisor status
+ 0x80x0 0000 0300 0001 sie Supervisor interrupt enable
+ 0x80x0 0000 0300 0002 stvec Supervisor trap vector base
+ 0x80x0 0000 0300 0003 sscratch Supervisor scratch register
+ 0x80x0 0000 0300 0004 sepc Supervisor exception program counter
+ 0x80x0 0000 0300 0005 scause Supervisor trap cause
+ 0x80x0 0000 0300 0006 stval Supervisor bad address or instruction
+ 0x80x0 0000 0300 0007 sip Supervisor interrupt pending
+ 0x80x0 0000 0300 0008 satp Supervisor address translation and protection
+
+RISC-V timer registers represent the timer state of a Guest VCPU and it has
+the following id bit patterns:
+ 0x8030 0000 04 <index into the kvm_riscv_timer struct:24>
+
+Following are the RISC-V timer registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x8030 0000 0400 0000 frequency Time base frequency (read-only)
+ 0x8030 0000 0400 0001 time Time value visible to Guest
+ 0x8030 0000 0400 0002 compare Time compare programmed by Guest
+ 0x8030 0000 0400 0003 state Time compare state (1 = ON or 0 = OFF)
+
+RISC-V F-extension registers represent the single precision floating point
+state of a Guest VCPU and it has the following id bit patterns:
+ 0x8020 0000 05 <index into the __riscv_f_ext_state struct:24>
+
+Following are the RISC-V F-extension registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x8020 0000 0500 0000 f[0] Floating point register 0
+ ...
+ 0x8020 0000 0500 001f f[31] Floating point register 31
+ 0x8020 0000 0500 0020 fcsr Floating point control and status register
+
+RISC-V D-extension registers represent the double precision floating point
+state of a Guest VCPU and it has the following id bit patterns:
+ 0x8020 0000 06 <index into the __riscv_d_ext_state struct:24> (fcsr)
+ 0x8030 0000 06 <index into the __riscv_d_ext_state struct:24> (non-fcsr)
+
+Following are the RISC-V D-extension registers:
+
+ Encoding Register Description
+------------------------------------------------------------------
+ 0x8030 0000 0600 0000 f[0] Floating point register 0
+ ...
+ 0x8030 0000 0600 001f f[31] Floating point register 31
+ 0x8020 0000 0600 0020 fcsr Floating point control and status register
+
+
4.69 KVM_GET_ONE_REG

Capability: KVM_CAP_ONE_REG
@@ -4542,6 +4680,23 @@ Note that KVM does not skip the faulting instruction as it does for
KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state
if it decides to decode and emulate the instruction.

+ /* KVM_EXIT_RISCV_SBI */
+ struct {
+ unsigned long extension_id;
+ unsigned long function_id;
+ unsigned long args[6];
+ unsigned long ret[2];
+ } riscv_sbi;
+If exit reason is KVM_EXIT_RISCV_SBI then it indicates that the VCPU has
+done a SBI call which is not handled by KVM RISC-V kernel module. The details
+of the SBI call are available in 'riscv_sbi' member of kvm_run structure. The
+'extension_id' field of 'riscv_sbi' represents SBI extension ID whereas the
+'function_id' field represents function ID of given SBI extension. The 'args'
+array field of 'riscv_sbi' represents parameters for the SBI call and 'ret'
+array field represents return values. The userspace should update the return
+values of SBI call before resuming the VCPU. For more details on RISC-V SBI
+spec refer, https://github.com/riscv/riscv-sbi-doc.
+
/* Fix the size of the union. */
char padding[256];
};
--
2.17.1
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