* Add riscv prefix to raise_exception function
* Add riscv prefix to CSR read/write functions
* Add riscv prefix to signal handler function
* Add riscv prefix to get fflags function
* Remove redundant declaration of riscv_cpu_init
  and rename cpu_riscv_init to riscv_cpu_init
* rename riscv_set_mode to riscv_cpu_set_mode
Signed-off-by: NMichael Clark <mjc@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

This adds the necessary minimum to support S-mode
virtualization for priv ISA >= v1.10
Signed-off-by: NMichael Clark <mjc@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Co-authored-by: NMatthew Suozzo <msuozzo@google.com>
Co-authored-by: NMichael Clark <mjc@sifive.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

Previous CSR code uses csr_read_helper and csr_write_helper
to update CSR registers however this interface prevents
atomic read/modify/write CSR operations; in addition
there is no trap-free method to access to CSRs due
to the monolithic CSR functions call longjmp.

The current iCSR interface is not safe to be called by
target/riscv/gdbstub.c as privilege checks or missing CSRs
may call longjmp to generate exceptions. It needs to
indicate existence so traps can be generated in the
CSR instruction helpers.

This commit moves CSR access from the monolithic switch
statements in target/riscv/op_helper.c into modular
read/write functions in target/riscv/csr.c using a new
function pointer table for dispatch (which can later
be used to allow CPUs to hook up model specific CSRs).

A read/modify/write interface is added to support atomic
CSR operations and a non-trapping interface is added
to allow exception-free access to CSRs by the debugger.

The CSR functions and CSR dispatch table are ordered
to match The RISC-V Instruction Set Manual, Volume II:
Privileged Architecture Version 1.10, 2.2 CSR Listing.

An API is added to allow derived cpu instances to modify
or implement new CSR operations.
Signed-off-by: NMichael Clark <mjc@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

* Add user-mode CSR defininitions.
* Reorder CSR definitions to match the specification.
* Change H mode interrupt comment to 'reserved'.
* Remove unused X_COP interrupt.
* Add user-mode interrupts.
* Remove erroneous until comments on machine mode interrupts.
* Move together paging mode and page table bit definitions.
* Move together interrupt and exception cause definitions.
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

This patch makes op_helper.c contain only instruction
operation helpers used by translate.c and moves any
unrelated cpu helpers into cpu_helper.c. No logic is
changed by this patch.
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

Change the API of riscv_set_local_interrupt to take a
write mask and value to allow setting and clearing of
multiple local interrupts atomically in a single call.
Rename the new function to riscv_cpu_update_mip.
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>
Signed-off-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180606152128.449-11-f4bug@amsat.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

These fields are marked WARL (Write Any Values, Reads
Legal Values) in the RISC-V Privileged Architecture
Specification so instead of raising exceptions,
illegal writes are silently dropped.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>

Vectored traps for asynchrounous interrupts are optional.
The mtvec/stvec mode field is WARL and hence does not trap
if an illegal value is written. Illegal values are ignored.

Later we can add RISCV_FEATURE_VECTORED_TRAPS however
until then the correct behavior for WARL (Write Any, Read
Legal) fields is to drop writes to unsupported bits.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>

Previously the mycycle/minstret CSRs and rdcycle/rdinstret
psuedo instructions would return the time as a proxy for an
increasing instruction counter in the absence of having a
precise instruction count. If QEMU is invoked with -icount,
the mcycle/minstret CSRs and rdcycle/rdinstret psuedo
instructions will return the instruction count.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>

Privileged ISA v1.9.1 defines mscounteren and mucounteren:

* mscounteren contains a mask of counters available to S-mode
* mucounteren contains a mask of counters available to U-mode

Privileged ISA v1.10 defines mcounteren and scounteren:

* mcounteren contains a mask of counters available to S-mode
* scounteren contains a mask of counters available to U-mode

mcounteren and scounteren CSR registers were implemented
however they were not honoured for counter accesses when
the privilege ISA was >= v1.10. This fix solves the issue
by coalescing the counter enable registers. In addition
the code now  generates illegal instruction exceptions
for accesses to the counter enabled registers depending
on the privileged ISA version.

- Coalesce mscounteren and mcounteren into one variable
- Coalesce mucounteren and scounteren into one variable
- Makes mcounteren and scounteren CSR accesses generate
  illegal instructions when the privileged ISA <= v1.9.1
- Makes mscounteren and mucounteren CSR accesses generate
  illegal instructions when the privileged ISA >= v1.10

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>

The mstatus.MXR alias in sstatus should only be writable
by S-mode if the privileged ISA version >= v1.10. Also MXR
was masked in sstatus CSR read but not sstatus CSR writes.
Now we correctly mask sstatus.mxr in both read and write.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>

satp is WARL so it should not trap on illegal writes, rather
it can be hardwired to zero and silently ignore illegal writes.

It seems the RISC-V WARL behaviour is preferred to having to
trap overhead versus simply reading back the value and checking
if the write took (saves hundreds of cycles and more complex
trap handling code).

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>

This change is a workaround for a bug where mstatus.FS
is not correctly reporting dirty after operations that
modify floating point registers. This a critical bug
or RISC-V in QEMU as it results in floating point
register file corruption when running SMP Linux due to
task migration and possibly uniprocessor Linux if
more than one process is using the FPU.

This workaround will return dirty if mstatus.FS is
switched from off to initial or clean. According to
the specification it is legal for an implementation
to return only off, or dirty.

Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: NRichard W.M. Jones <rjones@redhat.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>

Privileged control and status register helpers and page fault handling.
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NSagar Karandikar <sagark@eecs.berkeley.edu>
Signed-off-by: NMichael Clark <mjc@sifive.com>