Claudio Fontana <[email protected]> writes:
> Hi Alex, > > thanks for looking at this, > > On 6/16/20 4:16 PM, Alex Bennée wrote: >> >> Claudio Fontana <[email protected]> writes: >> >>> each accelerator registers a new "CpusAccel" interface >>> implementation on initialization, providing functions for >>> starting a vcpu, kicking a vcpu, and sychronizing state. >>> >>> This way the code in cpus.c is now all general softmmu code, >>> nothing accelerator-specific anymore. >>> >>> There is still some ifdeffery for WIN32 though. >>> >>> Signed-off-by: Claudio Fontana <[email protected]> >>> --- >>> MAINTAINERS | 1 + >>> accel/Makefile.objs | 2 +- >>> accel/kvm/Makefile.objs | 2 + >>> accel/kvm/kvm-all.c | 15 +- >>> accel/kvm/kvm-cpus.c | 94 +++++ >>> accel/kvm/kvm-cpus.h | 17 + >>> accel/qtest/Makefile.objs | 2 + >>> accel/qtest/qtest-cpus.c | 105 +++++ >>> accel/qtest/qtest-cpus.h | 17 + >>> accel/{ => qtest}/qtest.c | 7 + >>> accel/stubs/kvm-stub.c | 3 +- >>> accel/tcg/Makefile.objs | 1 + >>> accel/tcg/tcg-all.c | 12 +- >>> accel/tcg/tcg-cpus.c | 523 ++++++++++++++++++++++++ >>> accel/tcg/tcg-cpus.h | 17 + >>> hw/core/cpu.c | 1 + >>> include/sysemu/cpus.h | 32 ++ >>> include/sysemu/hw_accel.h | 57 +-- >>> include/sysemu/kvm.h | 2 +- >>> softmmu/cpus.c | 911 >>> ++++-------------------------------------- >>> stubs/Makefile.objs | 1 + >>> stubs/cpu-synchronize-state.c | 15 + >>> target/i386/Makefile.objs | 7 +- >>> target/i386/hax-all.c | 6 +- >>> target/i386/hax-cpus.c | 85 ++++ >>> target/i386/hax-cpus.h | 17 + >>> target/i386/hax-i386.h | 2 + >>> target/i386/hax-posix.c | 12 + >>> target/i386/hax-windows.c | 20 + >>> target/i386/hvf/Makefile.objs | 2 +- >>> target/i386/hvf/hvf-cpus.c | 141 +++++++ >>> target/i386/hvf/hvf-cpus.h | 17 + >>> target/i386/hvf/hvf.c | 3 + >>> target/i386/whpx-all.c | 3 + >>> target/i386/whpx-cpus.c | 96 +++++ >>> target/i386/whpx-cpus.h | 17 + >>> 36 files changed, 1362 insertions(+), 903 deletions(-) >>> create mode 100644 accel/kvm/kvm-cpus.c >>> create mode 100644 accel/kvm/kvm-cpus.h >>> create mode 100644 accel/qtest/Makefile.objs >>> create mode 100644 accel/qtest/qtest-cpus.c >>> create mode 100644 accel/qtest/qtest-cpus.h >>> rename accel/{ => qtest}/qtest.c (86%) >>> create mode 100644 accel/tcg/tcg-cpus.c >>> create mode 100644 accel/tcg/tcg-cpus.h >>> create mode 100644 stubs/cpu-synchronize-state.c >>> create mode 100644 target/i386/hax-cpus.c >>> create mode 100644 target/i386/hax-cpus.h >>> create mode 100644 target/i386/hvf/hvf-cpus.c >>> create mode 100644 target/i386/hvf/hvf-cpus.h >>> create mode 100644 target/i386/whpx-cpus.c >>> create mode 100644 target/i386/whpx-cpus.h >> >> Predictably for such a spider patch I got a bunch of conflicts >> attempting to merge on my testing branch so only a few comments. >> >>> >>> diff --git a/MAINTAINERS b/MAINTAINERS >>> index f308537d42..ef8cbb2680 100644 >>> --- a/MAINTAINERS >>> +++ b/MAINTAINERS >>> @@ -427,6 +427,7 @@ WHPX CPUs >>> M: Sunil Muthuswamy <[email protected]> >>> S: Supported >>> F: target/i386/whpx-all.c >>> +F: target/i386/whpx-cpus.c >>> F: target/i386/whp-dispatch.h >>> F: accel/stubs/whpx-stub.c >>> F: include/sysemu/whpx.h >>> diff --git a/accel/Makefile.objs b/accel/Makefile.objs >>> index ff72f0d030..c5e58eb53d 100644 >>> --- a/accel/Makefile.objs >>> +++ b/accel/Makefile.objs >>> @@ -1,5 +1,5 @@ >>> common-obj-$(CONFIG_SOFTMMU) += accel.o >>> -obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o >>> +obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/ >> >> This does raise the question if qtest is "just another" accelerator then >> should we not be creating a CONFIG_QTEST symbol for explicitness? >> >>> obj-$(CONFIG_KVM) += kvm/ >>> obj-$(CONFIG_TCG) += tcg/ >>> obj-$(CONFIG_XEN) += xen/ >> <snip> >>> +static void *qtest_cpu_thread_fn(void *arg) >>> +{ >>> +#ifdef _WIN32 >>> + error_report("qtest is not supported under Windows"); >>> + exit(1); >>> +#else >> >> This is literally impossible to build isn't it? >>> >>> static int qtest_init_accel(MachineState *ms) >>> { >>> + cpus_register_accel(&qtest_cpus); >>> return 0; >>> } >> >> I wonder if these register functions could be moved to initfns like we >> use for our hardware models? > > The context is the configure_accelerator() in vl.c , where we loop over > possible candidate accelerators > and try to initialize them. > > In this RFC the cpus_register_accel is triggered at accel_init_machine() time, > in the accelerator class init_machine() method, where we are trying to use a > specific accelerator. > > This is the case for qtest like for the other AccelClass types (tcg and the > hardware accelerators). > > If not in init_machine(), where would the registration best happen? Ahh I see - this is once the decision about which accelerator has been made. I was thinking along the lines of the init functions driven by: #define type_init(function) module_init(function, MODULE_INIT_QOM) which would then populate the list of available accelerators in a more QOM like manner. I assume having a completely configurable set of accelerators is the eventual aim of this? > >> >> <snip> >>> >>> +/* >>> + * every accelerator is supposed to register this. >>> + * Could be in the AccelClass instead, but ends up being too complicated >>> + * to access in practice, and inefficient for each call of each method. >>> + */ >>> +static CpusAccel cpus_accel; >>> + >> >> wait what? Does an indirection cause that much trouble? I'm surprised >> given how often we use it elsewhere in the code. I guess others might > > CpusAccel is not used elsewhere currently in the codebase, it's new, or what > do you mean? > >> argue for a full QOM-ification of the accelerator but I think we can at >> least have an indirection rather than a copy of the structure. >> >> > > As mentioned in v3 and v2, this is what we end up if we put CpusAccel inside > the AccelClass, > every time we need a vcpu kick, sync state, etc: > > 1) current_accel() function call > 2) pointer dereference (->accelerator) > 3) object_class_dynamic_cast_assert function call (ACCEL_GET_CLASS -> > OBJECT_CLASS_CHECK) > 4) pointer dereference (-> AccelCpusInterface) > 5) pointer dereference (-> method) > 6) function call ( ->synchronize_state(cpu)) > > So the code then would look like this (more or less, probably I would put > also an assert for non-NULL in there): > > VERSION A) > > void cpu_synchronize_state(CPUState *cpu) > { > ACCEL_GET_CLASS(current_accel())->cpus_int->synchronize_state(cpu); > } I don't think it has to be quite so extreme. I was just arguing for something along the lines of: static CpuAccel *accel; and void cpu_synchronize_state(CPUState *cpu) { if (accel && accel->synchronize_state) { accel->synchronize_state(cpu); } } > Instead with the current RFC code, this is what we end up with every > time we need a vcpu kick, sync state, etc: I don't think a pointer de-reference alone is super critical for something that happens on the outside of the main run loop. It might be a different argument if this was somewhere in the hot path. > Are you arguing in favor of VERSION A) here? Version C ;-) > > I would like to have an ACK from the owners of the hardware accels especially > that the additional overhead in this code path > is of negligible importance.. > > > Thank you for your comments, > > Ciao, > > Claudio -- Alex Bennée
