From: Dave Martin <Dave.Martin@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
libc-alpha@sourceware.org, Szabolcs Nagy <szabolcs.nagy@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Richard Sandiford <richard.sandiford@arm.com>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 11/27] arm64/sve: Core task context handling
Date: Thu, 17 Aug 2017 16:42:00 -0000 [thread overview]
Message-ID: <20170817164233.GJ6321@e103592.cambridge.arm.com> (raw)
In-Reply-To: <CAKv+Gu-Rei0LP9q77+KHtD4JqM-6j4XvQjG7oCLrjHx2M5DA7g@mail.gmail.com>
On Tue, Aug 15, 2017 at 06:31:05PM +0100, Ard Biesheuvel wrote:
> Hi Dave,
>
> On 9 August 2017 at 13:05, Dave Martin <Dave.Martin@arm.com> wrote:
> > This patch adds the core support for switching and managing the SVE
> > architectural state of user tasks.
[...]
> > +static u64 sve_cpacr_trap_on(u64 cpacr)
> > +{
> > + return cpacr & ~(u64)CPACR_EL1_ZEN_EL0EN;
> > +}
> > +
> > +static u64 sve_cpacr_trap_off(u64 cpacr)
> > +{
> > + return cpacr | CPACR_EL1_ZEN_EL0EN;
> > +}
> > +
> > +static void change_cpacr(u64 old, u64 new)
> > +{
> > + if (old != new)
> > + write_sysreg(new, CPACR_EL1);
> > +}
[...]
> > +static void task_fpsimd_load(void)
> > +{
> > + if (system_supports_sve() && test_thread_flag(TIF_SVE)) {
> > + unsigned int vl = current->thread.sve_vl;
> > +
> > + BUG_ON(!sve_vl_valid(vl));
> > + sve_load_state(sve_pffr(current),
> > + ¤t->thread.fpsimd_state.fpsr,
> > + sve_vq_from_vl(vl) - 1);
> > + } else
> > + fpsimd_load_state(¤t->thread.fpsimd_state);
> > +
>
> Please use braces consistently on all branches of an if ()
>
> > + if (system_supports_sve()) {
> > + u64 cpacr = read_sysreg(CPACR_EL1);
> > + u64 new_cpacr;
> > +
> > + /* Toggle SVE trapping for userspace if needed */
> > + if (test_thread_flag(TIF_SVE))
> > + new_cpacr = sve_cpacr_trap_off(cpacr);
> > + else
> > + new_cpacr = sve_cpacr_trap_on(cpacr);
> > +
> > + change_cpacr(cpacr, new_cpacr);
>
> I understand you want to avoid setting CPACR to the same value, but
> this does look a bit clunky IMO. Wouldn't it be much better to have a
> generic accessor with a mask and a value that encapsulates this?
For this I now have:
static void change_cpacr(u64 val, u64 mask)
{
u64 cpacr = read_sysreg(CPACR_EL1);
u64 new = (cpacr & ~mask) | val;
if (new != cpacr)
write_sysreg(new, CPACR_EL1);
}
static void sve_cpacr_trap_on(void)
{
change_cpacr(0, CPACR_EL1_ZEN_EL0EN);
}
static void sve_cpacr_trap_off(void)
{
change_cpacr(CPACR_EL1_ZEN_EL0EN, CPACR_EL1_ZEN_EL0EN);
}
This is stilla little verbose, but fairly clean. Possibly this was the
sort of thing you meant by a generic accessor.
What do you think?
[...]
Cheers
---Dave
next prev parent reply other threads:[~2017-08-17 16:42 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-09 12:05 [PATCH 00/27] ARM Scalable Vector Extension (SVE) Dave Martin
2017-08-09 12:06 ` [PATCH 01/27] regset: Add support for dynamically sized regsets Dave Martin
2017-08-18 11:52 ` Alex Bennée
2017-08-09 12:06 ` [PATCH 02/27] arm64: KVM: Hide unsupported AArch64 CPU features from guests Dave Martin
2017-08-16 11:11 ` Marc Zyngier
2017-08-16 20:32 ` Dave Martin
2017-08-17 8:46 ` Marc Zyngier
2017-08-17 9:57 ` Dave Martin
2017-08-09 12:06 ` [PATCH 09/27] arm64/sve: Signal frame and context structure definition Dave Martin
2017-08-22 10:22 ` Alex Bennée
2017-08-22 11:17 ` Dave Martin
2017-08-22 13:53 ` Alex Bennée
2017-08-22 14:21 ` Dave Martin
2017-08-22 15:03 ` Alex Bennée
2017-08-22 15:41 ` Dave Martin
2017-08-09 12:06 ` [PATCH 03/27] arm64: efi: Add missing Kconfig dependency on KERNEL_MODE_NEON Dave Martin
2017-08-18 12:02 ` Alex Bennée
2017-08-09 12:06 ` [PATCH 07/27] arm64/sve: Low-level SVE architectural state manipulation functions Dave Martin
2017-08-21 10:11 ` Alex Bennée
2017-08-21 14:38 ` Dave Martin
2017-08-09 12:06 ` [PATCH 08/27] arm64/sve: Kconfig update and conditional compilation support Dave Martin
2017-08-21 10:12 ` Alex Bennée
2017-08-09 12:06 ` [PATCH 04/27] arm64: Port deprecated instruction emulation to new sysctl interface Dave Martin
2017-08-18 12:09 ` Alex Bennée
2017-08-09 12:06 ` [PATCH 05/27] arm64: fpsimd: Simplify uses of {set,clear}_ti_thread_flag() Dave Martin
2017-08-15 17:11 ` Ard Biesheuvel
2017-08-18 16:36 ` [PATCH 05/27] arm64: fpsimd: Simplify uses of {set, clear}_ti_thread_flag() Alex Bennée
2017-08-09 12:07 ` [PATCH 12/27] arm64/sve: Support vector length resetting for new processes Dave Martin
2017-08-22 16:22 ` Alex Bennée
2017-08-22 17:22 ` Dave Martin
2017-08-09 12:07 ` [PATCH 14/27] arm64/sve: Backend logic for setting the vector length Dave Martin
2017-08-23 15:33 ` Alex Bennée
2017-08-23 17:30 ` Dave Martin
2017-08-09 12:07 ` [PATCH 11/27] arm64/sve: Core task context handling Dave Martin
2017-08-15 17:36 ` Ard Biesheuvel
2017-08-16 10:40 ` Dave Martin
2017-08-17 16:42 ` Dave Martin [this message]
2017-08-17 16:46 ` Ard Biesheuvel
2017-08-22 16:21 ` Alex Bennée
2017-08-22 17:20 ` Dave Martin
2017-08-22 18:39 ` Alex Bennée
2017-08-09 12:07 ` [PATCH 10/27] arm64/sve: Low-level CPU setup Dave Martin
2017-08-22 15:04 ` Alex Bennée
2017-08-22 15:33 ` Dave Martin
2017-08-09 12:07 ` [PATCH 13/27] arm64/sve: Signal handling support Dave Martin
2017-08-23 9:38 ` Alex Bennée
2017-08-23 11:30 ` Dave Martin
2017-08-09 12:07 ` [PATCH 06/27] arm64/sve: System register and exception syndrome definitions Dave Martin
2017-08-21 9:34 ` Alex Bennée
2017-08-21 12:34 ` Alex Bennée
2017-08-21 14:26 ` Dave Martin
2017-08-21 14:50 ` Alex Bennée
2017-08-21 15:20 ` Dave Martin
2017-08-21 15:34 ` Alex Bennée
2017-08-21 13:57 ` Dave Martin
2017-08-21 14:36 ` Alex Bennée
2017-08-09 12:07 ` [PATCH 15/27] arm64/sve: Probe SVE capabilities and usable vector lengths Dave Martin
2017-08-16 17:48 ` Suzuki K Poulose
2017-08-17 10:04 ` Dave Martin
2017-08-17 10:46 ` Suzuki K Poulose
2017-08-09 12:07 ` [PATCH 17/27] arm64/sve: Preserve SVE registers around EFI runtime service calls Dave Martin
2017-08-15 17:46 ` Ard Biesheuvel
2017-08-16 9:13 ` Dave Martin
2017-08-09 12:08 ` [PATCH 21/27] arm64/sve: KVM: Prevent guests from using SVE Dave Martin
2017-08-15 16:33 ` Marc Zyngier
2017-08-16 10:50 ` Dave Martin
2017-08-16 11:20 ` Marc Zyngier
2017-08-16 11:23 ` Marc Zyngier
2017-08-16 11:35 ` Dave Martin
2017-08-09 12:08 ` [PATCH 25/27] arm64/sve: Add documentation Dave Martin
2017-08-09 12:08 ` [RFC PATCH 26/27] arm64: signal: Report signal frame size to userspace via auxv Dave Martin
2017-08-09 12:08 ` [PATCH 19/27] arm64/sve: Add prctl controls for userspace vector length management Dave Martin
2017-08-09 12:08 ` [RFC PATCH 27/27] arm64/sve: signal: Include SVE when computing AT_MINSIGSTKSZ Dave Martin
2017-08-09 12:08 ` [PATCH 23/27] arm64/sve: KVM: Hide SVE from CPU features exposed to guests Dave Martin
2017-08-15 16:38 ` Marc Zyngier
2017-08-16 10:55 ` Dave Martin
2017-08-16 11:11 ` Marc Zyngier
2017-08-16 11:22 ` Dave Martin
2017-08-09 12:08 ` [PATCH 16/27] arm64/sve: Preserve SVE registers around kernel-mode NEON use Dave Martin
2017-08-15 17:38 ` Ard Biesheuvel
2017-08-09 12:08 ` [PATCH 20/27] arm64/sve: Add sysctl to set the default vector length for new processes Dave Martin
2017-08-09 12:08 ` [PATCH 24/27] arm64/sve: Detect SVE and activate runtime support Dave Martin
2017-08-16 17:53 ` Suzuki K Poulose
2017-08-17 10:01 ` Dave Martin
2017-08-09 12:08 ` [PATCH 22/27] arm64/sve: KVM: Treat guest SVE use as undefined instruction execution Dave Martin
2017-08-09 12:08 ` [PATCH 18/27] arm64/sve: ptrace and ELF coredump support Dave Martin
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