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Re: [Qemu-devel] [Qemu-arm] [PATCH v5 17/17] target/arm: Rely on hflags
From: |
Laurent Desnogues |
Subject: |
Re: [Qemu-devel] [Qemu-arm] [PATCH v5 17/17] target/arm: Rely on hflags correct in cpu_get_tb_cpu_state |
Date: |
Thu, 5 Sep 2019 17:40:21 +0200 |
On Thu, Sep 5, 2019 at 5:24 PM Alex Bennée <address@hidden> wrote:
>
>
> Richard Henderson <address@hidden> writes:
>
> > This is the payoff.
> >
> > From perf record -g data of ubuntu 18 boot and shutdown:
> >
> > BEFORE:
> >
> > - 23.02% 2.82% qemu-system-aar [.] helper_lookup_tb_ptr
> > - 20.22% helper_lookup_tb_ptr
> > + 10.05% tb_htable_lookup
> > - 9.13% cpu_get_tb_cpu_state
> > 3.20% aa64_va_parameters_both
> > 0.55% fp_exception_el
> >
> > - 11.66% 4.74% qemu-system-aar [.] cpu_get_tb_cpu_state
> > - 6.96% cpu_get_tb_cpu_state
> > 3.63% aa64_va_parameters_both
> > 0.60% fp_exception_el
> > 0.53% sve_exception_el
> >
> > AFTER:
> >
> > - 16.40% 3.40% qemu-system-aar [.] helper_lookup_tb_ptr
> > - 13.03% helper_lookup_tb_ptr
> > + 11.19% tb_htable_lookup
> > 0.55% cpu_get_tb_cpu_state
> >
> > 0.98% 0.71% qemu-system-aar [.] cpu_get_tb_cpu_state
> >
> > 0.87% 0.24% qemu-system-aar [.] rebuild_hflags_a64
> >
> > Before, helper_lookup_tb_ptr is the second hottest function in the
> > application, consuming almost a quarter of the runtime. Within the
> > entire execution, cpu_get_tb_cpu_state consumes about 12%.
> >
> > After, helper_lookup_tb_ptr has dropped to the fourth hottest function,
> > with consumption dropping to a sixth of the runtime. Within the
> > entire execution, cpu_get_tb_cpu_state has dropped below 1%, and the
> > supporting function to rebuild hflags also consumes about 1%.
> >
> > Assertions are retained for --enable-debug-tcg.
> >
> > Tested-by: Alex Bennée <address@hidden>
>
> Hmm something must have been missed for M-profile because:
>
> make run-tcg-tests-arm-softmmu V=1
>
> Leads to:
>
> timeout 15
> /home/alex/lsrc/qemu.git/builds/all.debug/arm-softmmu/qemu-system-arm
> -monitor none -display none -chardev
> file,path=test-armv6m-undef.out,id=output -semihosting -M microbit -kernel
> test-armv6m-undef
> qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)
>
> R00=00000000 R01=00000000 R02=00000000 R03=00000000
> R04=00000000 R05=00000000 R06=00000000 R07=00000000
> R08=00000000 R09=00000000 R10=00000000 R11=00000000
> R12=00000000 R13=20003fe0 R14=fffffff9 R15=000000c0
> XPSR=41000003 -Z-- T handler
> FPSCR: 00000000
> timeout: the monitored command dumped core
>
> But annoyingly not shown up by the debug-tcg verification. The commit
> before works fine.
There's a typo in the patch: that should not be CONFIG_TCG_DEBUG but
CONFIG_DEBUG_TCG. With this you should see the assert fire.
I let Richard know that there's an issue with the handling of CPSR E
flag (BE_DATA in hflags). I don't know if that applies to your test.
Thanks,
Laurent
> > Reviewed-by: Alex Bennée <address@hidden>
> > Signed-off-by: Richard Henderson <address@hidden>
> > ---
> > v2: Retain asserts for future debugging.
> > ---
> > target/arm/helper.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/target/arm/helper.c b/target/arm/helper.c
> > index d1bf71a260..5e4f996882 100644
> > --- a/target/arm/helper.c
> > +++ b/target/arm/helper.c
> > @@ -11211,12 +11211,15 @@ void HELPER(rebuild_hflags_a64)(CPUARMState *env,
> > int el)
> > void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
> > target_ulong *cs_base, uint32_t *pflags)
> > {
> > - uint32_t flags, pstate_for_ss;
> > + uint32_t flags = env->hflags;
> > + uint32_t pstate_for_ss;
> >
> > *cs_base = 0;
> > - flags = rebuild_hflags_internal(env);
> > +#ifdef CONFIG_TCG_DEBUG
> > + assert(flags == rebuild_hflags_internal(env));
> > +#endif
> >
> > - if (is_a64(env)) {
> > + if (FIELD_EX32(flags, TBFLAG_ANY, AARCH64_STATE)) {
> > *pc = env->pc;
> > if (cpu_isar_feature(aa64_bti, env_archcpu(env))) {
> > flags = FIELD_DP32(flags, TBFLAG_A64, BTYPE, env->btype);
>
>
> --
> Alex Bennée
>