draft: support for Hexagon VM

Status: boots linux kernel up to setup_command_line() before panic

Hacks:
* vmnewmap call not implemented (does get invoked by linux)
* vmyield call not implemented (does get invoked by linux)
* trap0 not quite right (not _yet_ invoked by linux)
... and more

Signed-off-by: Brian Cain <[email protected]>

docs/system/hexagon/hvm.rst

@@ -0,0 +1,186 @@
+Hexagon Virtual Machine
+=======================
+
+The hexagon virtual machine is a hypervisor that can partition a single
+Hexagon DSP among multiple guest operating systems, and abstracts the
+specific details of a DSP architectural revision for the sake of consistency
+among generations.
+
+The ``virt`` machine has Hexagon VM emulation enabled by default.
+
+Events
+------
+
+The guest operating system should register the Guest Event Vector Base
+via the ``vmsetvec`` virtual instruction at system startup.  The vector table
+and handlers are determined by the guest OS.
+
+Guests return from event handlers with ``vmrte``.  This instruction will restore
+the mode (user versus guest), interrupt enable state, PC, SP.
+
+.. list-table:: Event types
+   :header-rows: 1
+
+   * - Number
+     - Name
+     - Description
+     - Maskable
+     - Detail
+   * - 0
+     - Reserved
+     -
+     -
+     -
+   * - 1
+     - Machine check event
+     - unrecoverable VM state
+     - No
+     - execution terminates if unhandled
+   * - 2
+     - General exception
+     - internal hardware or software exception
+     - No
+     -
+   * - 3-4
+     - Reserved
+     -
+     -
+     -
+   * - 5
+     - ``trap0``
+     - ``trap0`` instruction
+     - No
+     -
+   * - 6
+     - Reserved
+     -
+     -
+     -
+   * - 7
+     - Interrupt
+     - external interrupts
+     - Yes
+     - increasing interrupt numbers have descending priority
+
+Startup
+-------
+In order to transition to user-mode, the guest OS must set the ``UM`` bit in
+the guest status register and specify the address to start executing in
+user mode in the guest event link register.
+
+Virtual Instructions
+--------------------
+
+.. list-table:: Virtual Instructions
+   :header-rows: 1
+
+   * - Instruction
+     - Behavior
+     - Operand
+     - Input
+     - Output
+   * - vmversion
+     - returns the VM version
+     - 0x0
+     - requested VM version
+     - provided VM version
+   * - vmrte
+     - return from event
+     - 0x1
+     - Event info in g3:0
+     - N/A
+   * - vmsetvec
+     - set event vector
+     - 0x2
+     - r0 is set to vector table addr
+     - r0 is 0 on success, 1 otherwise
+   * - vmsetie
+     - set interrupt enabled
+     - 0x3
+     - r0 is set to 1 to enable, 0 to disable
+     - previous IE bit is stored as LSB of r0
+   * - vmgetie
+     - get interrupt enabled
+     - 0x4
+     - N/A
+     - current IE bit is stored as LSB of r0
+   * - vmintop
+     - interrupt operation
+     - 0x5
+     - r0 = Interrupt Op, r1-r4: Depends on Op
+     - r0 - value depends on operation
+   * - vmclrmap
+     - clear virtual memory map
+     - 0xa
+     - r0 = Interrupt Op, r1-r4: Depends on Op
+     - r0 - value depends on operation
+   * - vmnewmap
+     - set new virtual memory map
+     - 0xb
+     - r0 contains logical address of new segment table, r1 =Type of translations
+     - r0 contains 0 on success, otherwise negative error code
+   * - vmcache
+     - VM cache control: not modeled
+     - 0xd
+     - r0 contains the operation to be performed, r1 = Starting virtual address, r2 contains the length in bytes
+     - r0 contains 0 on success, otherwise -1.  Cache behavior is not modeled so this operation always succeeds.
+   * - vmgettime
+     - Get virtual machine time
+     - 0xe
+     - N/A
+     - r0 contains the least significant 32 bits of timestamp, r1 contains the  most significant 32 bits of timestamp
+   * - vmsettime
+     - Set virtual machine time
+     - 0xf
+     - r0 contains the least significant 32 bits of timestamp, r1 contains the  most significant 32 bits of timestamp
+     - N/A
+   * - vmwait
+     - wait for interrupt
+     - 0x10
+     - N/A
+     - r0 contains the interrupt number of the interrupt waking the guest
+   * - vmyield
+     - voluntarily yield VM task
+     - 0x11
+     - N/A
+     - N/A
+   * - vmstart
+     - Create new virtual processor instance
+     - 0x12
+     - r0 contains the starting execution address, r1 contains the starting stack pointer
+     - r0 contains the Virtual processor number of new virtual processor on success, otherwise -1
+   * - vmstop
+     - terminate current virtual processor instance
+     - 0x13
+     - N/A
+     - N/A
+   * - vmvpid
+     - get the virtual processor ID
+     - 0x14
+     - N/A
+     - r0 contains the virtual processor number of virtual processor executing the instruction
+   * - vmsetregs
+     - Set guest registers
+     - 0x15
+     - r0-3 hold g0-3 values
+     - N/A
+   * - vmgetregs
+     - Get guest registers
+     - 0x16
+     - N/A
+     - r0-3 hold g0-3 values
+   * - vmtimerop
+     - perform an operation on a system timer
+     - 0x18
+     - getfreq = 0
+       getres = 1
+       gettime = 2
+       gettimeout = 3
+       settimeout = 4
+       deltatimeout = 5
+     - TBD
+   * - vmgetinfo
+     - Get system info
+     - 0x1a
+     - Index of the system info parameter: FIXME another table
+     - value of the indicated system info parameter

hw/hexagon/hexagon_testboard.c

@@ -180,6 +180,7 @@ static void hexagon_common_init(MachineState *machine, Rev_t rev,
         CPUHexagonState *env = &cpu->env;
         qemu_register_reset(do_cpu_reset, cpu);
 
+        qdev_prop_set_bit(DEVICE(cpu), "hexagon-vm", true);
         qdev_prop_set_uint32(DEVICE(cpu), "thread-count", machine->smp.cpus);
         qdev_prop_set_uint32(DEVICE(cpu), "config-table-addr",
             cfgExtensions->cfgbase);

target/hexagon/cpu.c

@@ -127,6 +127,7 @@ static Property hexagon_cpu_properties[] = {
     DEFINE_PROP_BOOL("isdben-dfd-enable", HexagonCPU, isdben_dfd_enable, false),
     DEFINE_PROP_BOOL("isdben-trusted", HexagonCPU, isdben_trusted, false),
     DEFINE_PROP_BOOL("isdben-secure", HexagonCPU, isdben_secure, false),
+    DEFINE_PROP_BOOL("hexagon-vm", HexagonCPU, hexagon_vm, false),
     DEFINE_PROP_STRING("dump-json-reg-file", HexagonCPU, dump_json_file),
 #endif
     DEFINE_PROP_UINT32("dsp-rev", HexagonCPU, rev_reg, 0),
@@ -573,11 +574,17 @@ static void hexagon_restore_state_to_opc(CPUState *cs,
 #if !defined(CONFIG_USER_ONLY)
 void hexagon_cpu_soft_reset(CPUHexagonState *env)
 {
+    CPUState *cs = env_cpu(env);
+    HexagonCPU *cpu = HEXAGON_CPU(cs);
     ARCH_SET_SYSTEM_REG(env, HEX_SREG_SSR, 0);
     hexagon_ssr_set_cause(env, HEX_CAUSE_RESET);
 
     target_ulong evb = ARCH_GET_SYSTEM_REG(env, HEX_SREG_EVB);
     ARCH_SET_THREAD_REG(env, HEX_REG_PC, evb);
+
+    if (cpu->hexagon_vm) {
+        ARCH_SET_SYSTEM_REG(env, HEX_SREG_IMASK, 0xffffffff);
+    }
 }
 #endif
 

target/hexagon/cpu.h

@@ -458,6 +458,7 @@ struct ArchCPU {
     bool isdben_dfd_enable;
     bool isdben_trusted;
     bool isdben_secure;
+    bool hexagon_vm;
 #endif
     uint32_t rev_reg;
     bool lldb_compat;

target/hexagon/gen_tcg.h

@@ -1437,6 +1437,8 @@
     do { RsV = RsV; } while (0)
 #define fGEN_TCG_Y2_icinva(SHORTCODE) \
     do { RsV = RsV; } while (0)
+#define fGEN_TCG_J2_trap1(SHORTCODE) \
+    do { (void) uiV; } while (0)
 #else
 /* data/insn cache ops can raise exceptions */
 #define fGEN_TCG_CACHEOP(HELPER) \

target/hexagon/gen_tcg_sys.h

@@ -135,4 +135,9 @@
         tcg_gen_extrh_i64_i32(ctx->t_sreg_new_value[HEX_SREG_SGP1], tmp); \
     } while (0)
 
+#define fGEN_TCG_J2_trap1(SHORTCODE) \
+    do { \
+        gen_vminst(ctx, uiV); \
+    } while (0)
+
 #endif

target/hexagon/genptr.c

@@ -1862,5 +1862,103 @@ static void gen_vtcm_memcpy(DisasContext *ctx, TCGv dst, TCGv src, TCGv size)
     gen_set_label(finish);
 }
 
+#if !defined(CONFIG_USER_ONLY)
+enum hex_virt_opc {
+    HEX_VIRT_VMVERSION = 0x00,
+    HEX_VIRT_VMRETURN = 0x01,
+    HEX_VIRT_VMSETVEC = 0x02,
+    HEX_VIRT_VMSETIE = 0x03,
+    HEX_VIRT_VMGETIE = 0x04,
+    HEX_VIRT_VMINTOP = 0x05,
+    HEX_VIRT_VMCLRMAP = 0x0A,
+    HEX_VIRT_VMNEWMAP = 0x0B,
+    HEX_VIRT_VMCACHECTL = 0x0D,
+    HEX_VIRT_VMGETTIME = 0x0E,
+    HEX_VIRT_VMSETTIME = 0x0F,
+    HEX_VIRT_VMWAIT = 0x10,
+    HEX_VIRT_VMYIELD = 0x11,
+    HEX_VIRT_VMSTART = 0x12,
+    HEX_VIRT_VMSTOP = 0x13,
+    HEX_VIRT_VMVMPID = 0x14,
+    HEX_VIRT_VMSETREGS = 0x15,
+    HEX_VIRT_VMGETREGS = 0x16,
+    HEX_VIRT_VMTIMEROP = 0x18,
+    HEX_VIRT_VMPMUCTRL = 0x19,
+    HEX_VIRT_VMGETINFO = 0x1A,
+};
+
+#include "hex_vm.c.inc"
+
+static void gen_vminst(DisasContext *ctx, int operand)
+{
+    if (!ctx->has_hexagon_vm) {
+        /* FIXME: raise an exception instead? */
+        return;
+    }
+
+    /* TODO: when swapping guest/user, must exchange GOSP, R29... */
+    switch (operand) {
+    case HEX_VIRT_VMVERSION:
+        gen_vmversion();
+        break;
+    case HEX_VIRT_VMSETREGS:
+        gen_vmsetregs();
+        break;
+    case HEX_VIRT_VMGETREGS:
+        gen_vmgetregs();
+        break;
+    case HEX_VIRT_VMSETIE:
+        gen_vmsetie();
+        break;
+    case HEX_VIRT_VMGETIE:
+        gen_vmgetie();
+        break;
+    case HEX_VIRT_VMVMPID:
+        gen_vmvpid();
+        break;
+    case HEX_VIRT_VMCACHECTL:
+        gen_vmcache();
+        break;
+    case HEX_VIRT_VMSTOP:
+        gen_vmstop();
+        break;
+    case HEX_VIRT_VMYIELD:
+        gen_vmyield();
+        break;
+    case HEX_VIRT_VMGETTIME:
+        gen_vmgettime();
+        break;
+    case HEX_VIRT_VMRETURN:
+        gen_vmrte();
+        break;
+    case HEX_VIRT_VMCLRMAP:
+        gen_vmclrmap();
+        break;
+    case HEX_VIRT_VMNEWMAP:
+        gen_vmnewmap();
+        break;
+    case HEX_VIRT_VMSETVEC:
+        gen_vmsetvec();
+        break;
+    case HEX_VIRT_VMINTOP:
+        gen_vmintop();
+        break;
+    case HEX_VIRT_VMGETINFO:
+        gen_vmgetinfo();
+        break;
+    case HEX_VIRT_VMTIMEROP:
+        gen_vmtimerop();
+        break;
+
+
+    default:
+        /* FIXME: Invalid packet exception? */
+        fprintf(stderr, "Unknown VM instruction 0x%08x\n", operand);
+        g_assert_not_reached();
+        break;
+    }
+}
+#endif
+
 #include "tcg_funcs_generated.c.inc"
 #include "tcg_func_table_generated.c.inc"

target/hexagon/helper.h

@@ -148,6 +148,7 @@ DEF_HELPER_2(greg_read, i32, env, i32)
 DEF_HELPER_2(greg_read_pair, i64, env, i32)
 DEF_HELPER_1(inc_gcycle_xt, void, env)
 DEF_HELPER_3(modify_ssr, void, env, i32, i32)
+DEF_HELPER_2(modify_syscfg, void, env, i32)
 DEF_HELPER_1(pending_interrupt, void, env)
 DEF_HELPER_3(raise_stack_overflow, void, env, i32, i32)
 DEF_HELPER_1(resched, void, env)