From: Alan Hayward <Alan.Hayward@arm.com>
To: Dave P Martin <Dave.Martin@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"Catalin Marinas" <Catalin.Marinas@arm.com>,
"Will Deacon" <Will.Deacon@arm.com>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Szabolcs Nagy" <Szabolcs.Nagy@arm.com>,
"Richard Sandiford" <Richard.Sandiford@arm.com>,
"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"gdb@sourceware.org" <gdb@sourceware.org>,
"Yao Qi" <Yao.Qi@arm.com>, nd <nd@arm.com>
Subject: Re: [PATCH v2 14/28] arm64/sve: Backend logic for setting the vector length
Date: Wed, 20 Sep 2017 10:59:55 +0000 [thread overview]
Message-ID: <FC5BA359-D37C-493C-87CD-146B83D3CCB5@arm.com> (raw)
In-Reply-To: <1504198860-12951-15-git-send-email-Dave.Martin@arm.com>
(Resending without disclaimer)
> On 31 Aug 2017, at 18:00, Dave Martin <Dave.Martin@arm.com> wrote:
>
> +int sve_set_vector_length(struct task_struct *task,
> + unsigned long vl, unsigned long flags)
> +{
> + WARN_ON(task == current && preemptible());
> +
> + if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT |
> + PR_SVE_SET_VL_ONEXEC))
> + return -EINVAL;
> +
> + if (!sve_vl_valid(vl))
> + return -EINVAL;
> +
> + /*
> + * Clamp to the maximum vector length that VL-agnostic SVE code can
> + * work with. A flag may be assigned in the future to allow setting
> + * of larger vector lengths without confusing older software.
> + */
> + if (vl > SVE_VL_ARCH_MAX)
> + vl = SVE_VL_ARCH_MAX;
> +
> + vl = find_supported_vector_length(vl);
> +
Given, sve_set_vector_length is called when setting the vector length in
PTRACE_SETREGSET, it looks to me like if you set VL to a value that’s not
supported by the hardware, then it’s going to round down to the previous value.
Is that correct? I’m not sure if that’s explained in the docs?
What happens if you give a vl value lower than the min supported value in the
hardware?
> +/*
> + * All vector length selection from userspace comes through here.
> + * We're on a slow path, so some sanity-checks are included.
> + * If things go wrong there's a bug somewhere, but try to fall back to a
> + * safe choice.
> + */
> +static unsigned int find_supported_vector_length(unsigned int vl)
> +{
> + int bit;
> + int max_vl = sve_max_vl;
> +
> + if (WARN_ON(!sve_vl_valid(vl)))
> + vl = SVE_VL_MIN;
> +
> + if (WARN_ON(!sve_vl_valid(max_vl)))
> + max_vl = SVE_VL_MIN;
> +
> + if (vl > max_vl)
> + vl = max_vl;
> +
> + bit = find_next_bit(sve_vq_map, SVE_VQ_MAX,
> + vq_to_bit(sve_vq_from_vl(vl)));
> + return sve_vl_from_vq(bit_to_vq(bit));
> +}
> +
Thanks,
Alan.
WARNING: multiple messages have this Message-ID (diff)
From: Alan.Hayward@arm.com (Alan Hayward)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 14/28] arm64/sve: Backend logic for setting the vector length
Date: Wed, 20 Sep 2017 10:59:55 +0000 [thread overview]
Message-ID: <FC5BA359-D37C-493C-87CD-146B83D3CCB5@arm.com> (raw)
In-Reply-To: <1504198860-12951-15-git-send-email-Dave.Martin@arm.com>
(Resending without disclaimer)
> On 31 Aug 2017, at 18:00, Dave Martin <Dave.Martin@arm.com> wrote:
>
> +int sve_set_vector_length(struct task_struct *task,
> + unsigned long vl, unsigned long flags)
> +{
> + WARN_ON(task == current && preemptible());
> +
> + if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT |
> + PR_SVE_SET_VL_ONEXEC))
> + return -EINVAL;
> +
> + if (!sve_vl_valid(vl))
> + return -EINVAL;
> +
> + /*
> + * Clamp to the maximum vector length that VL-agnostic SVE code can
> + * work with. A flag may be assigned in the future to allow setting
> + * of larger vector lengths without confusing older software.
> + */
> + if (vl > SVE_VL_ARCH_MAX)
> + vl = SVE_VL_ARCH_MAX;
> +
> + vl = find_supported_vector_length(vl);
> +
Given, sve_set_vector_length is called when setting the vector length in
PTRACE_SETREGSET, it looks to me like if you set VL to a value that?s not
supported by the hardware, then it?s going to round down to the previous value.
Is that correct? I?m not sure if that?s explained in the docs?
What happens if you give a vl value lower than the min supported value in the
hardware?
> +/*
> + * All vector length selection from userspace comes through here.
> + * We're on a slow path, so some sanity-checks are included.
> + * If things go wrong there's a bug somewhere, but try to fall back to a
> + * safe choice.
> + */
> +static unsigned int find_supported_vector_length(unsigned int vl)
> +{
> + int bit;
> + int max_vl = sve_max_vl;
> +
> + if (WARN_ON(!sve_vl_valid(vl)))
> + vl = SVE_VL_MIN;
> +
> + if (WARN_ON(!sve_vl_valid(max_vl)))
> + max_vl = SVE_VL_MIN;
> +
> + if (vl > max_vl)
> + vl = max_vl;
> +
> + bit = find_next_bit(sve_vq_map, SVE_VQ_MAX,
> + vq_to_bit(sve_vq_from_vl(vl)));
> + return sve_vl_from_vq(bit_to_vq(bit));
> +}
> +
Thanks,
Alan.
next prev parent reply other threads:[~2017-09-20 10:59 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
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 [this message]
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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