From: Catalin Marinas <catalin.marinas@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>,
linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Peter Collingbourne <pcc@google.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl()
Date: Wed, 22 Jul 2020 11:28:47 +0100 [thread overview]
Message-ID: <20200722102845.GA27540@gaia> (raw)
In-Reply-To: <20200720170050.GJ30452@arm.com>
On Mon, Jul 20, 2020 at 06:00:50PM +0100, Dave P Martin wrote:
> On Mon, Jul 20, 2020 at 04:30:35PM +0100, Kevin Brodsky wrote:
> > On 15/07/2020 18:08, Catalin Marinas wrote:
> > >+void mte_thread_switch(struct task_struct *next)
> > >+{
> > >+ if (!system_supports_mte())
> > >+ return;
> > >+
> > >+ /* avoid expensive SCTLR_EL1 accesses if no change */
> > >+ if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0)
> >
> > I think this could be improved by checking whether `next` is a kernel
> > thread, in which case thread.sctlr_tcf0 is 0 but there is no point in
> > setting SCTLR_EL1.TCF0, since there should not be any access via TTBR0.
>
> Out of interest, do we have a nice way of testing for a kernel thread
> now?
>
> I remember fpsimd_thread_switch() used to check for task->mm, but we
> seem to have got rid of that at some point. set_mm() can defeat this,
> and anyway the heavy lifting for FPSIMD is now deferred until returning
> to userspace.
I think a better way is (current->flags & PF_KTHREAD). kthread_use_mm()
indeed changes current->mm.
--
Catalin
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Peter Collingbourne <pcc@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl()
Date: Wed, 22 Jul 2020 11:28:47 +0100 [thread overview]
Message-ID: <20200722102845.GA27540@gaia> (raw)
In-Reply-To: <20200720170050.GJ30452@arm.com>
On Mon, Jul 20, 2020 at 06:00:50PM +0100, Dave P Martin wrote:
> On Mon, Jul 20, 2020 at 04:30:35PM +0100, Kevin Brodsky wrote:
> > On 15/07/2020 18:08, Catalin Marinas wrote:
> > >+void mte_thread_switch(struct task_struct *next)
> > >+{
> > >+ if (!system_supports_mte())
> > >+ return;
> > >+
> > >+ /* avoid expensive SCTLR_EL1 accesses if no change */
> > >+ if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0)
> >
> > I think this could be improved by checking whether `next` is a kernel
> > thread, in which case thread.sctlr_tcf0 is 0 but there is no point in
> > setting SCTLR_EL1.TCF0, since there should not be any access via TTBR0.
>
> Out of interest, do we have a nice way of testing for a kernel thread
> now?
>
> I remember fpsimd_thread_switch() used to check for task->mm, but we
> seem to have got rid of that at some point. set_mm() can defeat this,
> and anyway the heavy lifting for FPSIMD is now deferred until returning
> to userspace.
I think a better way is (current->flags & PF_KTHREAD). kthread_use_mm()
indeed changes current->mm.
--
Catalin
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next prev parent reply other threads:[~2020-07-22 10:28 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 17:08 [PATCH v7 00/26] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 01/29] arm64: mte: system register definitions Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 02/29] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 03/29] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 04/29] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 05/29] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 06/29] mm: Add PG_arch_2 page flag Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 07/29] mm: Preserve the PG_arch_2 flag in __split_huge_page_tail() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 08/29] arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 09/29] arm64: mte: Tags-aware copy_{user_,}highpage() implementations Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 10/29] arm64: Avoid unnecessary clear_user_page() indirection Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 11/29] arm64: mte: Tags-aware aware memcmp_pages() implementation Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 12/29] arm64: mte: Handle the MAIR_EL1 changes for late CPU bring-up Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 13/29] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 14/29] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 15/29] mm: Introduce arch_validate_flags() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 16/29] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 17/29] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-07-20 15:30 ` Kevin Brodsky
2020-07-20 15:30 ` Kevin Brodsky
2020-07-20 17:00 ` Dave Martin
2020-07-20 17:00 ` Dave Martin
2020-07-22 10:28 ` Catalin Marinas [this message]
2020-07-22 10:28 ` Catalin Marinas
2020-07-23 19:33 ` Kevin Brodsky
2020-07-23 19:33 ` Kevin Brodsky
2020-07-22 11:09 ` Catalin Marinas
2020-07-22 11:09 ` Catalin Marinas
2020-08-04 19:34 ` Kevin Brodsky
2020-08-04 19:34 ` Kevin Brodsky
2020-08-05 9:24 ` Catalin Marinas
2020-08-05 9:24 ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 19/29] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 20/29] arm64: mte: Restore the GCR_EL1 register after a suspend Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 21/29] arm64: mte: Allow {set,get}_tagged_addr_ctrl() on non-current tasks Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 22/29] arm64: mte: ptrace: Add PTRACE_{PEEK,POKE}MTETAGS support Catalin Marinas
2020-08-13 14:01 ` Luis Machado
2020-08-13 14:01 ` Luis Machado
2020-08-22 10:56 ` Catalin Marinas
2020-08-22 10:56 ` Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 23/29] arm64: mte: ptrace: Add NT_ARM_TAGGED_ADDR_CTRL regset Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 24/29] fs: Handle intra-page faults in copy_mount_options() Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 25/29] mm: Add arch hooks for saving/restoring tags Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 26/29] arm64: mte: Enable swap of tagged pages Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 27/29] arm64: mte: Save tags when hibernating Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 28/29] arm64: mte: Kconfig entry Catalin Marinas
2020-07-15 17:08 ` [PATCH v7 29/29] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-07-27 16:36 ` Szabolcs Nagy
2020-07-27 16:36 ` Szabolcs Nagy
2020-07-28 11:08 ` Dave Martin
2020-07-28 11:08 ` Dave Martin
2020-07-28 14:53 ` Szabolcs Nagy
2020-07-28 14:53 ` Szabolcs Nagy
2020-07-28 19:59 ` Catalin Marinas
2020-07-28 19:59 ` Catalin Marinas
2020-08-03 12:43 ` Szabolcs Nagy
2020-08-03 12:43 ` Szabolcs Nagy
2020-08-07 15:19 ` Catalin Marinas
2020-08-07 15:19 ` Catalin Marinas
2020-08-10 14:13 ` Szabolcs Nagy
2020-08-10 14:13 ` Szabolcs Nagy
2020-08-11 17:20 ` Catalin Marinas
2020-08-11 17:20 ` Catalin Marinas
2020-08-12 12:45 ` Szabolcs Nagy
2020-08-12 12:45 ` Szabolcs Nagy
2020-08-19 9:54 ` Catalin Marinas
2020-08-19 9:54 ` Catalin Marinas
2020-08-20 16:43 ` Szabolcs Nagy
2020-08-20 16:43 ` Szabolcs Nagy
2020-08-20 17:27 ` Paul Eggert
2020-08-20 17:27 ` Paul Eggert
2020-08-22 11:31 ` Catalin Marinas
2020-08-22 11:31 ` Catalin Marinas
2020-08-22 11:28 ` Catalin Marinas
2020-08-22 11:28 ` Catalin Marinas
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