From: "Alex Bennée" <alex.bennee@linaro.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org, robhenry@microsoft.com,
mahmoudabdalghany@outlook.com, aaron@os.amperecomputing.com,
cota@braap.org, Paolo Bonzini <pbonzini@redhat.com>,
kuhn.chenqun@huawei.com
Subject: Re: [PATCH v2 17/21] accel/tcg: cache single instruction TB on pending replay exception
Date: Thu, 11 Feb 2021 20:00:40 +0000 [thread overview]
Message-ID: <87h7mis6xc.fsf@linaro.org> (raw)
In-Reply-To: <67c46489-08b7-fce5-91c9-8416f9164456@linaro.org>
Richard Henderson <richard.henderson@linaro.org> writes:
> On 2/10/21 2:10 PM, Alex Bennée wrote:
>> Again there is no reason to jump through the nocache hoops to execute
>> a single instruction block. We do have to add an additional wrinkle to
>> the cpu_handle_interrupt case to ensure we let through a TB where we
>> have specifically disabled icount for the block.
>
> Can you say more about this? Because...
>
>> if (unlikely(qatomic_read(&cpu->exit_request))
>> || (icount_enabled()
>> + && (cpu->cflags_next_tb == -1 || cpu->cflags_next_tb & CF_USE_ICOUNT)
>> && cpu_neg(cpu)->icount_decr.u16.low + cpu->icount_extra == 0)) {
>
> ... this does not appear to match. You're checking that icount has been
> explicitly *enabled*?
If icount has been enabled and we are using the default cflags or
enabled and we have the explicit CF_ICOUNT. The replay exception leg
explicitly disables icount because otherwise we'd never actually execute
the block because we have a budget of 0 cycles left. Previously we ran
that block at the exception handling point - now we fall through and
have to make sure we don't trigger an IRQ.
> Or am I reading the logic backward and only if icount is
> enabled will we take EXCP_INTERRUPT?
Or I guess we have an exit_request which hasn't been handled yet but
there is no EXCP_ pending.
>
>
> r~
--
Alex Bennée
next prev parent reply other threads:[~2021-02-11 20:26 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 22:10 [PATCH v2 00/21] plugins/next pre-PR (hwprofile, regression fixes, icount count fix) Alex Bennée
2021-02-10 22:10 ` [PATCH v2 01/21] hw/virtio/pci: include vdev name in registered PCI sections Alex Bennée
2021-02-10 22:10 ` [PATCH v2 02/21] plugins: add API to return a name for a IO device Alex Bennée
2021-02-10 22:10 ` [PATCH v2 03/21] plugins: new hwprofile plugin Alex Bennée
2021-02-10 22:10 ` [PATCH v2 04/21] contrib: Don't use '#' flag of printf format Alex Bennée
2021-02-10 22:10 ` [PATCH v2 05/21] contrib: Fix some code style problems, ERROR: "foo * bar" should be "foo *bar" Alex Bennée
2021-02-10 22:10 ` [PATCH v2 06/21] contrib: Add spaces around operator Alex Bennée
2021-02-10 22:10 ` [PATCH v2 07/21] contrib: space required after that ',' Alex Bennée
2021-02-10 22:10 ` [PATCH v2 08/21] contrib: Open brace '{' following struct go on the same line Alex Bennée
2021-02-10 22:10 ` [PATCH v2 09/21] accel/tcg/plugin-gen: fix the call signature for inline callbacks Alex Bennée
2021-02-10 22:10 ` [PATCH v2 10/21] exec: Move TranslationBlock typedef to qemu/typedefs.h Alex Bennée
2021-02-11 10:14 ` Philippe Mathieu-Daudé
2021-02-11 10:24 ` Alex Bennée
2021-02-10 22:10 ` [PATCH v2 11/21] accel/tcg: Create io_recompile_replay_branch hook Alex Bennée
2021-02-11 10:12 ` Philippe Mathieu-Daudé
2021-02-10 22:10 ` [PATCH v2 12/21] target/mips: Create mips_io_recompile_replay_branch Alex Bennée
2021-02-11 10:10 ` Philippe Mathieu-Daudé
2021-02-10 22:10 ` [PATCH v2 13/21] target/sh4: Create superh_io_recompile_replay_branch Alex Bennée
2021-02-11 10:13 ` Philippe Mathieu-Daudé
2021-02-10 22:10 ` [PATCH v2 14/21] tests/plugin: expand insn test to detect duplicate instructions Alex Bennée
2021-02-10 22:10 ` [PATCH v2 15/21] tests/acceptance: add a new set of tests to exercise plugins Alex Bennée
2021-02-11 10:31 ` Philippe Mathieu-Daudé
2021-02-11 18:59 ` Wainer dos Santos Moschetta
2021-02-11 19:51 ` Wainer dos Santos Moschetta
2021-02-10 22:10 ` [PATCH v2 16/21] accel/tcg: actually cache our partial icount TB Alex Bennée
2021-02-11 10:21 ` Philippe Mathieu-Daudé
2021-02-11 18:48 ` Richard Henderson
2021-02-12 15:40 ` Philippe Mathieu-Daudé
2021-02-12 17:06 ` Alex Bennée
2021-02-11 18:48 ` Richard Henderson
2021-02-10 22:10 ` [PATCH v2 17/21] accel/tcg: cache single instruction TB on pending replay exception Alex Bennée
2021-02-11 19:12 ` Richard Henderson
2021-02-11 20:00 ` Alex Bennée [this message]
2021-02-10 22:10 ` [PATCH v2 18/21] accel/tcg: re-factor non-RAM execution code Alex Bennée
2021-02-11 19:19 ` Richard Henderson
2021-02-10 22:10 ` [PATCH v2 19/21] accel/tcg: remove CF_NOCACHE and special cases Alex Bennée
2021-02-10 22:10 ` [PATCH v2 20/21] accel/tcg: allow plugin instrumentation to be disable via cflags Alex Bennée
2021-02-12 0:53 ` Aaron Lindsay via
2021-02-12 11:22 ` Alex Bennée
2021-02-12 14:31 ` Aaron Lindsay via
2021-02-12 14:59 ` Alex Bennée
2021-02-12 14:43 ` Alex Bennée
2021-02-12 15:41 ` Aaron Lindsay via
2021-02-12 16:04 ` Alex Bennée
2021-02-12 16:50 ` Aaron Lindsay via
2021-02-12 17:19 ` Alex Bennée
2021-02-16 10:34 ` Alex Bennée
2021-02-17 16:32 ` Aaron Lindsay via
2021-02-12 16:00 ` Alex Bennée
2021-02-12 17:04 ` Aaron Lindsay via
2021-02-10 22:10 ` [PATCH v2 21/21] tests/acceptance: add a new tests to detect counting errors Alex Bennée
2021-02-11 10:24 ` Philippe Mathieu-Daudé
2021-02-11 19:56 ` Wainer dos Santos Moschetta
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