| Message ID | 20230824221440.484675-13-dbarboza@ventanamicro.com |
|---|---|
| State | New |
| Headers | show |
| Series | riscv: 'max' CPU, detect user choice in TCG | expand |
On Thu, Aug 24, 2023 at 07:14:32PM -0300, Daniel Henrique Barboza wrote: > The 'any' CPU type was introduced in commit dc5bd18fa5725 ("RISC-V CPU > Core Definition"), being around since the beginning. It's not an easy > CPU to use: it's undocumented and its name doesn't tell users much about > what the CPU is supposed to bring. 'git log' doesn't help us either in > knowing what was the original design of this CPU type. > > The closest we have is a comment from Alistair [1] where he recalls from > memory that the 'any' CPU is supposed to behave like the newly added > 'max' CPU. He also suggested that the 'any' CPU should be removed. > > The default CPUs are rv32 and rv64, so removing the 'any' CPU will have > impact only on users that might have a script that uses '-cpu any'. > And those users are better off using the default CPUs or the new 'max' > CPU. > > We would love to just remove the code and be done with it, but one does > not simply remove a feature in QEMU. We'll put the CPU in quarantine > first, letting users know that we have the intent of removing it in the > future. > > [1] https://lists.gnu.org/archive/html/qemu-devel/2023-07/msg02891.html > > Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com> > Reviewed-by: Alistair Francis <alistair.francis@wdc.com> > --- > docs/about/deprecated.rst | 12 ++++++++++++ > target/riscv/cpu.c | 5 +++++ > 2 files changed, 17 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 92a2bafd2b..4ced7427ac 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -371,6 +371,18 @@ QEMU's ``vhost`` feature, which would eliminate the high latency costs under > which the 9p ``proxy`` backend currently suffers. However as of to date nobody > has indicated plans for such kind of reimplementation unfortunately. > > +RISC-V 'any' CPU type ``-cpu any`` (since 8.2) > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +The 'any' CPU type was introduced back in 2018 and has been around since the > +initial RISC-V QEMU port. Its usage has always been unclear: users don't know > +what to expect from a CPU called 'any', and in fact the CPU does not do anything > +special that aren't already done by the default CPUs rv32/rv64. ^ isn't > + > +After the introduction of the 'max' CPU type RISC-V now has a good coverage ^ , > +of generic CPUs: rv32 and rv64 as default CPUs and 'max' as a feature complete > +CPU for both 32 and 64 bit builds. Users are then discouraged to use the 'any' > +CPU type starting in 8.2. > > Block device options > '''''''''''''''''''' > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c > index 8dc85f75bb..913b64264f 100644 > --- a/target/riscv/cpu.c > +++ b/target/riscv/cpu.c > @@ -1522,6 +1522,11 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp) > RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(dev); > Error *local_err = NULL; > > + if (object_dynamic_cast(OBJECT(dev), TYPE_RISCV_CPU_ANY) != NULL) { > + warn_report("The 'any' CPU is deprecated and will be " > + "removed in the future."); > + } > + > cpu_exec_realizefn(cs, &local_err); > if (local_err != NULL) { > error_propagate(errp, local_err); > -- > 2.41.0 > > Besides the text edits, Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 92a2bafd2b..4ced7427ac 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -371,6 +371,18 @@ QEMU's ``vhost`` feature, which would eliminate the high latency costs under which the 9p ``proxy`` backend currently suffers. However as of to date nobody has indicated plans for such kind of reimplementation unfortunately. +RISC-V 'any' CPU type ``-cpu any`` (since 8.2) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The 'any' CPU type was introduced back in 2018 and has been around since the +initial RISC-V QEMU port. Its usage has always been unclear: users don't know +what to expect from a CPU called 'any', and in fact the CPU does not do anything +special that aren't already done by the default CPUs rv32/rv64. + +After the introduction of the 'max' CPU type RISC-V now has a good coverage +of generic CPUs: rv32 and rv64 as default CPUs and 'max' as a feature complete +CPU for both 32 and 64 bit builds. Users are then discouraged to use the 'any' +CPU type starting in 8.2. Block device options '''''''''''''''''''' diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c index 8dc85f75bb..913b64264f 100644 --- a/target/riscv/cpu.c +++ b/target/riscv/cpu.c @@ -1522,6 +1522,11 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp) RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(dev); Error *local_err = NULL; + if (object_dynamic_cast(OBJECT(dev), TYPE_RISCV_CPU_ANY) != NULL) { + warn_report("The 'any' CPU is deprecated and will be " + "removed in the future."); + } + cpu_exec_realizefn(cs, &local_err); if (local_err != NULL) { error_propagate(errp, local_err);
The 'any' CPU type was introduced in commit dc5bd18fa5725 ("RISC-V CPU Core Definition"), being around since the beginning. It's not an easy CPU to use: it's undocumented and its name doesn't tell users much about what the CPU is supposed to bring. 'git log' doesn't help us either in knowing what was the original design of this CPU type. The closest we have is a comment from Alistair [1] where he recalls from memory that the 'any' CPU is supposed to behave like the newly added 'max' CPU. He also suggested that the 'any' CPU should be removed. The default CPUs are rv32 and rv64, so removing the 'any' CPU will have impact only on users that might have a script that uses '-cpu any'. And those users are better off using the default CPUs or the new 'max' CPU. We would love to just remove the code and be done with it, but one does not simply remove a feature in QEMU. We'll put the CPU in quarantine first, letting users know that we have the intent of removing it in the future. [1] https://lists.gnu.org/archive/html/qemu-devel/2023-07/msg02891.html Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> --- docs/about/deprecated.rst | 12 ++++++++++++ target/riscv/cpu.c | 5 +++++ 2 files changed, 17 insertions(+)