Re: [Qemu-devel] [PATCH v1 21/21] RISC-V Build Infrastructure

[Michael Clark]

On Fri, 5 Jan 2018 at 5:55 AM, Antony Pavlov <address@hidden>
wrote:

> On Wed,  3 Jan 2018 13:44:25 +1300
> Michael Clark <address@hidden> wrote:
>
> > This adds RISC-V into the build system enabling the following targets:
> >
> > - riscv32-softmmu
> > - riscv64-softmmu
> > - riscv32-linux-user
> > - riscv64-linux-user
> >
>
> ...
>
> > diff --git a/default-configs/riscv32-softmmu.mak
> b/default-configs/riscv32-softmmu.mak
> > new file mode 100644
> > index 0000000..f9e7421
> > --- /dev/null
> > +++ b/default-configs/riscv32-softmmu.mak
> > @@ -0,0 +1,4 @@
> > +# Default configuration for riscv-softmmu
> > +
> > +CONFIG_SERIAL=y
> > +CONFIG_VIRTIO=y
> > diff --git a/default-configs/riscv64-linux-user.mak
> b/default-configs/riscv64-linux-user.mak
> > new file mode 100644
> > index 0000000..865b362
> > --- /dev/null
> > +++ b/default-configs/riscv64-linux-user.mak
> > @@ -0,0 +1 @@
> > +# Default configuration for riscv-linux-user
> > diff --git a/default-configs/riscv64-softmmu.mak
> b/default-configs/riscv64-softmmu.mak
> > new file mode 100644
> > index 0000000..f9e7421
> > --- /dev/null
> > +++ b/default-configs/riscv64-softmmu.mak
> > @@ -0,0 +1,4 @@
> > +# Default configuration for riscv-softmmu
> > +
> > +CONFIG_SERIAL=y
> > +CONFIG_VIRTIO=y
> > diff --git a/hw/riscv/Makefile.objs b/hw/riscv/Makefile.objs
> > new file mode 100644
> > index 0000000..a0c31ae
> > --- /dev/null
> > +++ b/hw/riscv/Makefile.objs
> > @@ -0,0 +1,12 @@
> > +obj-y += riscv_elf.o
> > +obj-y += riscv_htif.o
> > +obj-y += riscv_hart.o
> > +obj-y += sifive_e300.o
> > +obj-y += sifive_clint.o
> > +obj-y += sifive_prci.o
> > +obj-y += sifive_plic.o
> > +obj-y += sifive_u500.o
> > +obj-y += sifive_uart.o
> > +obj-y += spike_v1_09.o
> > +obj-y += spike_v1_10.o
> > +obj-y += virt.o
>
> According to https://www.sifive.com/products/freedom/
> Freedom E300 Platform uses RV32IMAC Architecture
> and Freedom U500 Platform uses RV64GC Architecture.
>
> Which means that qemu-system-riscv32 has to have E300 support but not U500
> support.
> qemu-system-riscv64 has to have U500 support but not E300 support.
>
> However please see this log:
>
> riscv-qemu$ ./riscv32-softmmu/qemu-system-riscv32 -M ?
> Supported machines are:
> none                 empty machine
> sifive_e300          RISC-V Board compatible with SiFive E300 SDK
> sifive_u500          RISC-V Board compatible with SiFive U500 SDK <<<<<<
> U500 in 32-bit mode
> spike_v1.10          RISC-V Spike Board (Privileged ISA v1.10)
> spike_v1.9           RISC-V Spike Board (Privileged ISA v1.9.1) (default)
> virt                 RISC-V VirtIO Board (Privileged spec v1.10)
> riscv-qemu$ ./riscv64-softmmu/qemu-system-riscv64 -M ?
> Supported machines are:
> none                 empty machine
> sifive_e300          RISC-V Board compatible with SiFive E300 SDK <<<<<<
> E300 in 64-bit mode
> sifive_u500          RISC-V Board compatible with SiFive U500 SDK
> spike_v1.10          RISC-V Spike Board (Privileged ISA v1.10)
> spike_v1.9           RISC-V Spike Board (Privileged ISA v1.9.1) (default)
> virt                 RISC-V VirtIO Board (Privileged spec v1.10)
>
> I propose at least this fixup:
>
> diff --git a/default-configs/riscv32-softmmu.mak
> b/default-configs/riscv32-softmmu.mak
> index f9e742120c..6a807f5f96 100644
> --- a/default-configs/riscv32-softmmu.mak
> +++ b/default-configs/riscv32-softmmu.mak
> @@ -1,4 +1,5 @@
> -# Default configuration for riscv-softmmu
> +# Default configuration for riscv32-softmmu
>
>  CONFIG_SERIAL=y
>  CONFIG_VIRTIO=y
> +CONFIG_SIFIVE_E300=y
> diff --git a/default-configs/riscv64-softmmu.mak
> b/default-configs/riscv64-softmmu.mak
> index f9e742120c..1a0349fe27 100644
> --- a/default-configs/riscv64-softmmu.mak
> +++ b/default-configs/riscv64-softmmu.mak
> @@ -1,4 +1,5 @@
> -# Default configuration for riscv-softmmu
> +# Default configuration for riscv64-softmmu
>
>  CONFIG_SERIAL=y
>  CONFIG_VIRTIO=y
> +CONFIG_SIFIVE_U500=y
> diff --git a/hw/riscv/Makefile.objs b/hw/riscv/Makefile.objs
> index a0c31ae25e..bac5faa603 100644
> --- a/hw/riscv/Makefile.objs
> +++ b/hw/riscv/Makefile.objs
> @@ -1,11 +1,11 @@
>  obj-y += riscv_elf.o
>  obj-y += riscv_htif.o
>  obj-y += riscv_hart.o
> -obj-y += sifive_e300.o
> +obj-$(CONFIG_SIFIVE_E300) += sifive_e300.o
>  obj-y += sifive_clint.o
>  obj-y += sifive_prci.o
>  obj-y += sifive_plic.o
> -obj-y += sifive_u500.o
> +obj-$(CONFIG_SIFIVE_U500) += sifive_u500.o
>  obj-y += sifive_uart.o
>  obj-y += spike_v1_09.o
>  obj-y += spike_v1_10.o


I’ll check whether there are 64-bit E series chips. Actually the key
distinction is no MMU and we don’t yet disable the MMU in the machine.

I’ll ask SiFive whether they want to restrict the “bitness”. There is
actually no reason why the machine can’t be invoked as 64-bit.

As far as I know the RTL is parametiazable and the 32-bit cores are
generated from the same RTL source using the rocket chip generator however
that’s something i’ll have to check. i.e. we may not want to restrict the
options here.

The machines are deliberately called E300 and U500 to refer to a generic
series and in future there will be a machine with the U54-MC which is a
particular instantiation. So in that respect the “series” machines are
generic.

It’s on our todo list to add support to disable the MMU but HiFive1
binaries will run anyway because they don’t touch the ‘satp’ CSR and take
the cpu out of Mbare adressing mode. I’d rank disabling the MMU on the E
series as a higher priority than restricting bitness.

In any case i’ll check if SiFive can parameterize a 64-bit E series with no
MMU, tightly coupled memory, etc. I can’t tell that for sure until I ask.

A HiFive1 machine of course should be 32-bit only, when we add one, but the
generic E series machine can run 32-bit HiFive1 binaries when invoked using
qemu-system-riscv32

I’ll ask...