From: Catalin Marinas <catalin.marinas@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: linux-arch@vger.kernel.org, libc-alpha@sourceware.org,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
"Richard Sandiford" <richard.sandiford@arm.com>,
"Will Deacon" <will.deacon@arm.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 11/28] arm64/sve: Core task context handling
Date: Fri, 6 Oct 2017 16:33:13 +0100 [thread overview]
Message-ID: <20171006153312.cushhcb4m2qc4kwd@armageddon.cambridge.arm.com> (raw)
In-Reply-To: <20171006151528.GB3611@e103592.cambridge.arm.com>
On Fri, Oct 06, 2017 at 04:15:28PM +0100, Dave P Martin wrote:
> On Fri, Oct 06, 2017 at 02:36:40PM +0100, Catalin Marinas wrote:
> > On Fri, Oct 06, 2017 at 02:10:09PM +0100, Dave P Martin wrote:
> > > On Thu, Oct 05, 2017 at 12:28:35PM +0100, Catalin Marinas wrote:
> > > > On Tue, Oct 03, 2017 at 12:33:03PM +0100, Dave P Martin wrote:
> > > > > TIF_FOREIGN_FPSTATE's meaning is expanded to cover SVE, but otherwise
> > > > > unchanged:
> > > > >
> > > > > * If a task is running and !TIF_FOREIGN_FPSTATE, then the the CPU
> > > > > registers of the CPU the task is running on contain the authoritative
> > > > > FPSIMD/SVE state of the task. The backing memory may be stale.
> > > > >
> > > > > * Otherwise (i.e., task not running, or task running and
> > > > > TIF_FOREIGN_FPSTATE), the task's FPSIMD/SVE backing memory is
> > > > > authoritative. If additionally per_cpu(fpsimd_last_state,
> > > > > task->fpsimd_state.cpu) == &task->fpsimd_state.cpu, then
> > > > > task->fpsimd_state.cpu's registers are also up to date for task, but
> > > > > not authorititive: the current FPSIMD/SVE state may be read from
> > > > > them, but they must not be written.
> > > > >
> > > > > The FPSIMD/SVE backing memory is selected by TIF_SVE:
> > > > >
> > > > > * TIF_SVE set: Zn (incorporating Vn in bits[127:0]), Pn and FFR are
> > > > > stored in task->thread.sve_state, formatted appropriately for vector
> > > > > length task->thread.sve_vl. task->thread.sve_state must point to a
> > > > > valid buffer at least sve_state_size(task) bytes in size.
> >
> > "Zn [...] stored in task->thread.sve_state" - is this still true with
> > the changes you proposed? I guess even without these changes, you have
> > situations where the hardware regs are out of sync with sve_state (see
> > more below).
>
> I guess I need to tweak the wording here.
>
> TIF_SVE says where the vector state should be loaded/stored from,
> but does not say whether the data is up to date in memory, or when
> it should be loaded/stored.
>
> The latter is described by a cocktail of different things including
> which bit of kernel code we are executing if any, whether the task
> is running/stopped etc., TIF_FOREIGN_FPSTATE,
> task->thread.fpsimd_state.cpu and per_cpu(fpsimd_last_state).
>
> Does this make any better sense of my code below?
Yes, it looks fine.
--
Catalin
WARNING: multiple messages have this Message-ID (diff)
From: catalin.marinas@arm.com (Catalin Marinas)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 11/28] arm64/sve: Core task context handling
Date: Fri, 6 Oct 2017 16:33:13 +0100 [thread overview]
Message-ID: <20171006153312.cushhcb4m2qc4kwd@armageddon.cambridge.arm.com> (raw)
In-Reply-To: <20171006151528.GB3611@e103592.cambridge.arm.com>
On Fri, Oct 06, 2017 at 04:15:28PM +0100, Dave P Martin wrote:
> On Fri, Oct 06, 2017 at 02:36:40PM +0100, Catalin Marinas wrote:
> > On Fri, Oct 06, 2017 at 02:10:09PM +0100, Dave P Martin wrote:
> > > On Thu, Oct 05, 2017 at 12:28:35PM +0100, Catalin Marinas wrote:
> > > > On Tue, Oct 03, 2017 at 12:33:03PM +0100, Dave P Martin wrote:
> > > > > TIF_FOREIGN_FPSTATE's meaning is expanded to cover SVE, but otherwise
> > > > > unchanged:
> > > > >
> > > > > * If a task is running and !TIF_FOREIGN_FPSTATE, then the the CPU
> > > > > registers of the CPU the task is running on contain the authoritative
> > > > > FPSIMD/SVE state of the task. The backing memory may be stale.
> > > > >
> > > > > * Otherwise (i.e., task not running, or task running and
> > > > > TIF_FOREIGN_FPSTATE), the task's FPSIMD/SVE backing memory is
> > > > > authoritative. If additionally per_cpu(fpsimd_last_state,
> > > > > task->fpsimd_state.cpu) == &task->fpsimd_state.cpu, then
> > > > > task->fpsimd_state.cpu's registers are also up to date for task, but
> > > > > not authorititive: the current FPSIMD/SVE state may be read from
> > > > > them, but they must not be written.
> > > > >
> > > > > The FPSIMD/SVE backing memory is selected by TIF_SVE:
> > > > >
> > > > > * TIF_SVE set: Zn (incorporating Vn in bits[127:0]), Pn and FFR are
> > > > > stored in task->thread.sve_state, formatted appropriately for vector
> > > > > length task->thread.sve_vl. task->thread.sve_state must point to a
> > > > > valid buffer at least sve_state_size(task) bytes in size.
> >
> > "Zn [...] stored in task->thread.sve_state" - is this still true with
> > the changes you proposed? I guess even without these changes, you have
> > situations where the hardware regs are out of sync with sve_state (see
> > more below).
>
> I guess I need to tweak the wording here.
>
> TIF_SVE says where the vector state should be loaded/stored from,
> but does not say whether the data is up to date in memory, or when
> it should be loaded/stored.
>
> The latter is described by a cocktail of different things including
> which bit of kernel code we are executing if any, whether the task
> is running/stopped etc., TIF_FOREIGN_FPSTATE,
> task->thread.fpsimd_state.cpu and per_cpu(fpsimd_last_state).
>
> Does this make any better sense of my code below?
Yes, it looks fine.
--
Catalin
next prev parent reply other threads:[~2017-10-06 15:33 UTC|newest]
Thread overview: 224+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 17:00 [PATCH v2 00/28] ARM Scalable Vector Extension (SVE) Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 01/28] regset: Add support for dynamically sized regsets Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 02/28] arm64: KVM: Hide unsupported AArch64 CPU features from guests Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 14:37 ` Alex Bennée
2017-09-13 14:37 ` Alex Bennée
2017-09-13 14:37 ` Alex Bennée
2017-09-15 0:04 ` Dave Martin
2017-09-15 0:04 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 03/28] arm64: efi: Add missing Kconfig dependency on KERNEL_MODE_NEON Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 04/28] arm64: Port deprecated instruction emulation to new sysctl interface Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 05/28] arm64: fpsimd: Simplify uses of {set,clear}_ti_thread_flag() Dave Martin
2017-08-31 17:00 ` [PATCH v2 05/28] arm64: fpsimd: Simplify uses of {set, clear}_ti_thread_flag() Dave Martin
2017-08-31 17:00 ` [PATCH v2 06/28] arm64/sve: System register and exception syndrome definitions Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 14:48 ` Alex Bennée
2017-09-13 14:48 ` Alex Bennée
2017-09-13 14:48 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 07/28] arm64/sve: Low-level SVE architectural state manipulation functions Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 15:39 ` Alex Bennée
2017-09-13 15:39 ` Alex Bennée
2017-09-13 15:39 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 08/28] arm64/sve: Kconfig update and conditional compilation support Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 09/28] arm64/sve: Signal frame and context structure definition Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 13:36 ` Catalin Marinas
2017-09-13 13:36 ` Catalin Marinas
2017-09-13 21:33 ` Dave Martin
2017-09-13 21:33 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 10/28] arm64/sve: Low-level CPU setup Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 13:32 ` Catalin Marinas
2017-09-13 13:32 ` Catalin Marinas
2017-09-13 19:21 ` Dave Martin
2017-09-13 19:21 ` Dave Martin
2017-09-13 19:21 ` Dave Martin
2017-10-05 10:47 ` Dave Martin
2017-10-05 10:47 ` Dave Martin
2017-10-05 11:04 ` Suzuki K Poulose
2017-10-05 11:04 ` Suzuki K Poulose
2017-10-05 11:22 ` Dave Martin
2017-10-05 11:22 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 11/28] arm64/sve: Core task context handling Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 14:33 ` Catalin Marinas
2017-09-13 14:33 ` Catalin Marinas
2017-09-14 19:55 ` Dave Martin
2017-09-14 19:55 ` Dave Martin
2017-09-20 13:58 ` Catalin Marinas
2017-09-20 13:58 ` Catalin Marinas
2017-10-03 11:11 ` Dave Martin
2017-10-03 11:11 ` Dave Martin
2017-10-04 17:29 ` Catalin Marinas
2017-10-04 17:29 ` Catalin Marinas
2017-10-03 11:33 ` Dave Martin
2017-10-03 11:33 ` Dave Martin
2017-10-05 11:28 ` Catalin Marinas
2017-10-05 11:28 ` Catalin Marinas
2017-10-06 13:10 ` Dave Martin
2017-10-06 13:10 ` Dave Martin
2017-10-06 13:36 ` Catalin Marinas
2017-10-06 13:36 ` Catalin Marinas
2017-10-06 15:15 ` Dave Martin
2017-10-06 15:15 ` Dave Martin
2017-10-06 15:33 ` Catalin Marinas [this message]
2017-10-06 15:33 ` Catalin Marinas
2017-09-13 17:26 ` Catalin Marinas
2017-09-13 17:26 ` Catalin Marinas
2017-09-13 19:17 ` Dave Martin
2017-09-13 19:17 ` Dave Martin
2017-09-13 22:21 ` Catalin Marinas
2017-09-13 22:21 ` Catalin Marinas
2017-09-14 19:40 ` Dave Martin
2017-09-14 19:40 ` Dave Martin
2017-09-19 17:13 ` Catalin Marinas
2017-09-19 17:13 ` Catalin Marinas
2017-08-31 17:00 ` [PATCH v2 12/28] arm64/sve: Support vector length resetting for new processes Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 8:47 ` Alex Bennée
2017-09-14 8:47 ` Alex Bennée
2017-09-14 8:47 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 13/28] arm64/sve: Signal handling support Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 9:30 ` Alex Bennée
2017-09-14 9:30 ` Alex Bennée
2017-09-14 9:30 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 14/28] arm64/sve: Backend logic for setting the vector length Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-13 17:29 ` Catalin Marinas
2017-09-13 17:29 ` Catalin Marinas
2017-09-13 19:06 ` Dave Martin
2017-09-13 19:06 ` Dave Martin
2017-09-13 22:11 ` Catalin Marinas
2017-09-13 22:11 ` Catalin Marinas
2017-10-05 16:42 ` Dave Martin
2017-10-05 16:42 ` Dave Martin
2017-10-05 16:53 ` Catalin Marinas
2017-10-05 16:53 ` Catalin Marinas
2017-10-05 17:04 ` Dave Martin
2017-10-05 17:04 ` Dave Martin
2017-09-20 10:57 ` Alan Hayward
2017-09-20 10:57 ` Alan Hayward
2017-09-20 10:59 ` Alan Hayward
2017-09-20 10:59 ` Alan Hayward
2017-09-20 11:09 ` Dave Martin
2017-09-20 11:09 ` Dave Martin
2017-09-20 18:08 ` Alan Hayward
2017-09-20 18:08 ` Alan Hayward
2017-09-21 11:19 ` Dave Martin
2017-09-21 11:19 ` Dave Martin
2017-09-21 11:57 ` Alan Hayward
2017-09-21 11:57 ` Alan Hayward
2017-08-31 17:00 ` [PATCH v2 15/28] arm64: cpufeature: Move sys_caps_initialised declarations Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 9:33 ` Alex Bennée
2017-09-14 9:33 ` Alex Bennée
2017-09-14 9:33 ` Alex Bennée
2017-09-14 9:35 ` Suzuki K Poulose
2017-09-14 9:35 ` Suzuki K Poulose
2017-08-31 17:00 ` [PATCH v2 16/28] arm64/sve: Probe SVE capabilities and usable vector lengths Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 9:45 ` Alex Bennée
2017-09-14 9:45 ` Alex Bennée
2017-09-14 9:45 ` Alex Bennée
2017-09-28 14:22 ` Dave Martin
2017-09-28 14:22 ` Dave Martin
2017-09-28 17:32 ` Alex Bennée
2017-09-28 17:32 ` Alex Bennée
2017-09-28 17:32 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 17/28] arm64/sve: Preserve SVE registers around kernel-mode NEON use Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 10:52 ` Alex Bennée
2017-09-14 10:52 ` Alex Bennée
2017-09-14 10:52 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 18/28] arm64/sve: Preserve SVE registers around EFI runtime service calls Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 11:01 ` Alex Bennée
2017-09-14 11:01 ` Alex Bennée
2017-09-14 11:01 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-06 16:21 ` Okamoto, Takayuki
2017-09-06 16:21 ` Okamoto, Takayuki
2017-09-06 18:16 ` Dave Martin
2017-09-06 18:16 ` Dave Martin
2017-09-07 5:11 ` Okamoto, Takayuki
2017-09-07 5:11 ` Okamoto, Takayuki
2017-09-07 5:11 ` Okamoto, Takayuki
2017-09-08 13:11 ` Dave Martin
2017-09-08 13:11 ` Dave Martin
2017-09-14 12:57 ` Alex Bennée
2017-09-14 12:57 ` Alex Bennée
2017-09-14 12:57 ` Alex Bennée
2017-09-28 14:57 ` Dave Martin
2017-09-28 14:57 ` Dave Martin
2017-09-29 12:46 ` Dave Martin
2017-09-29 12:46 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 20/28] arm64/sve: Add prctl controls for userspace vector length management Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 13:02 ` Alex Bennée
2017-09-14 13:02 ` Alex Bennée
2017-09-14 13:02 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 21/28] arm64/sve: Add sysctl to set the default vector length for new processes Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 13:05 ` Alex Bennée
2017-09-14 13:05 ` Alex Bennée
2017-09-14 13:05 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 22/28] arm64/sve: KVM: Prevent guests from using SVE Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 13:28 ` Alex Bennée
2017-09-14 13:28 ` Alex Bennée
2017-09-14 13:28 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 23/28] arm64/sve: KVM: Treat guest SVE use as undefined instruction execution Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 13:30 ` Alex Bennée
2017-09-14 13:30 ` Alex Bennée
2017-09-14 13:30 ` Alex Bennée
2017-09-14 13:31 ` Alex Bennée
2017-09-14 13:31 ` Alex Bennée
2017-09-14 13:31 ` Alex Bennée
2017-09-29 13:00 ` Dave Martin
2017-09-29 13:00 ` Dave Martin
2017-09-29 14:43 ` Alex Bennée
2017-09-29 14:43 ` Alex Bennée
2017-09-29 14:43 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 24/28] arm64/sve: KVM: Hide SVE from CPU features exposed to guests Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-09-14 13:32 ` Alex Bennée
2017-09-14 13:32 ` Alex Bennée
2017-09-14 13:32 ` Alex Bennée
2017-08-31 17:00 ` [PATCH v2 25/28] arm64/sve: Detect SVE and activate runtime support Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` [PATCH v2 26/28] arm64/sve: Add documentation Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-10-05 16:39 ` Szabolcs Nagy
2017-10-05 16:39 ` Szabolcs Nagy
2017-10-05 17:02 ` Dave Martin
2017-10-05 17:02 ` Dave Martin
2017-10-06 15:43 ` Szabolcs Nagy
2017-10-06 15:43 ` Szabolcs Nagy
2017-10-06 17:37 ` Dave Martin
2017-10-06 17:37 ` Dave Martin
2017-10-09 9:34 ` Alex Bennée
2017-10-09 9:34 ` Alex Bennée
2017-10-09 9:34 ` Alex Bennée
2017-10-09 9:49 ` Dave Martin
2017-10-09 9:49 ` Dave Martin
2017-10-09 14:07 ` Alex Bennée
2017-10-09 14:07 ` Alex Bennée
2017-10-09 14:07 ` Alex Bennée
2017-10-09 16:20 ` Dave Martin
2017-10-09 16:20 ` Dave Martin
2017-08-31 17:00 ` [RFC PATCH v2 27/28] arm64: signal: Report signal frame size to userspace via auxv Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:00 ` Dave Martin
2017-08-31 17:01 ` [RFC PATCH v2 28/28] arm64/sve: signal: Include SVE when computing AT_MINSIGSTKSZ Dave Martin
2017-08-31 17:01 ` Dave Martin
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