From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Shuah Khan <skhan@linuxfoundation.org>,
Shuah Khan <shuah@kernel.org>,
Alan Hayward <alan.hayward@arm.com>,
Luis Machado <luis.machado@arm.com>,
Salil Akerkar <Salil.Akerkar@arm.com>,
Basant Kumar Dwivedi <Basant.KumarDwivedi@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kselftest@vger.kernel.org,
Richard Sandiford <Richard.Sandiford@arm.com>
Subject: Re: [PATCH v1 12/38] arm64/sme: Provide ABI documentation for SME
Date: Tue, 12 Oct 2021 09:23:21 +0100 [thread overview]
Message-ID: <20211012082321.GN2700@arm.com> (raw)
In-Reply-To: <YWSaHaJOIbEigw4w@sirena.org.uk>
The 10/11/2021 21:10, Mark Brown wrote:
> On Mon, Oct 11, 2021 at 03:19:37PM +0100, Szabolcs Nagy wrote:
>
> > if fork resets tpidr2 then returning to a stack frame
> > that set tpidr2 could cause clobbered za state.
> > (userspace can fix this up, but if we want this case
> > to work then it's better to fix it on the kernel side)
>
> OK, that makes sense. I've changed the code and the kselftest so that
> TPIDR2 is preserved on thread creation.
does thread creation have to work the same way as fork?
(in a pthread_create child we want tpidr2 to be 0,
since it represents thread specific data. in a fork
child we want to preserve tpidr2 to mirror the
state of the parent as much as possible)
for sme pcs to work, the libc has to be updated anyway,
so we can change the clone child to set tpidr2. however
that's not atomic wrt thread creation. i don't think we
aim to support async-signal-safe za usage in the pcs so
this is not a problem, but if the kernel did the work
then the situation would be clearer in userspace.
i'm not sure when to do tpidr2=0 exactly, but something
like CLONE_SETTLS is set or child runs on a new stack
would work for me. if that's too ugly then preserving
tpidr2 in the child is fine.
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next prev parent reply other threads:[~2021-10-12 8:26 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 18:11 [PATCH v1 00/38] arm64/sme: Initial support for the Scalable Matrix Extension Mark Brown
2021-09-30 18:11 ` [PATCH v1 01/38] arm64/fp: Reindent fpsimd_save() Mark Brown
2021-10-11 9:39 ` Jonathan Cameron
2021-10-11 13:02 ` Mark Brown
2021-09-30 18:11 ` [PATCH v1 02/38] arm64/sve: Remove sve_load_from_fpsimd_state() Mark Brown
2021-09-30 18:11 ` [PATCH v1 03/38] arm64/sve: Make access to FFR optional Mark Brown
2021-09-30 18:11 ` [PATCH v1 04/38] arm64/sve: Rename find_supported_vector_length() Mark Brown
2021-09-30 18:11 ` [PATCH v1 05/38] arm64/sve: Use accessor functions for vector lengths in thread_struct Mark Brown
2021-09-30 18:11 ` [PATCH v1 06/38] arm64/sve: Put system wide vector length information into structs Mark Brown
2021-10-01 3:13 ` kernel test robot
2021-09-30 18:11 ` [PATCH v1 07/38] arm64/sve: Explicitly load vector length when restoring SVE state Mark Brown
2021-09-30 18:11 ` [PATCH v1 08/38] arm64/sve: Track vector lengths for tasks in an array Mark Brown
2021-10-11 10:20 ` Jonathan Cameron
2021-10-11 13:14 ` Mark Brown
2021-10-11 13:18 ` Jonathan Cameron
2021-09-30 18:11 ` [PATCH v1 09/38] arm64/sve: Make sysctl interface for SVE reusable by SME Mark Brown
2021-09-30 18:11 ` [PATCH v1 10/38] arm64/sve: Generalise vector length configuration prctl() for SME Mark Brown
2021-10-11 10:27 ` Jonathan Cameron
2021-10-11 13:18 ` Mark Brown
2021-09-30 18:11 ` [PATCH v1 11/38] selftests: arm64: Parameterise ptrace vector length information Mark Brown
2021-09-30 18:11 ` [PATCH v1 12/38] arm64/sme: Provide ABI documentation for SME Mark Brown
2021-10-08 14:11 ` Alan Hayward
2021-10-08 15:28 ` Mark Brown
2021-10-08 16:45 ` Alan Hayward
2021-10-08 17:04 ` Mark Brown
2021-10-11 11:15 ` Alan Hayward
2021-10-11 11:48 ` Mark Brown
2021-10-11 11:05 ` Jonathan Cameron
2021-10-11 13:20 ` Mark Brown
2021-10-11 13:17 ` Szabolcs Nagy
2021-10-11 13:23 ` Mark Brown
2021-10-11 14:19 ` Szabolcs Nagy
2021-10-11 20:10 ` Mark Brown
2021-10-12 8:23 ` Szabolcs Nagy [this message]
2021-10-13 18:37 ` Mark Brown
2021-10-14 9:57 ` Szabolcs Nagy
2021-09-30 18:11 ` [PATCH v1 13/38] arm64/sme: System register and exception syndrome definitions Mark Brown
2021-09-30 18:11 ` [PATCH v1 14/38] arm64/sme: Define macros for manually encoding SME instructions Mark Brown
2021-09-30 18:11 ` [PATCH v1 15/38] arm64/sme: Early CPU setup for SME Mark Brown
2021-09-30 18:11 ` [PATCH v1 16/38] arm64/sme: Basic enumeration support Mark Brown
2021-09-30 18:11 ` [PATCH v1 17/38] arm64/sme: Identify supported SME vector lengths at boot Mark Brown
2021-09-30 18:11 ` [PATCH v1 18/38] arm64/sme: Implement sysctl to set the default vector length Mark Brown
2021-09-30 18:11 ` [PATCH v1 19/38] arm64/sme: Implement vector length configuration prctl()s Mark Brown
2021-10-01 5:20 ` kernel test robot
2021-10-01 12:40 ` Mark Brown
2021-10-08 1:32 ` [kbuild-all] " Chen, Rong A
2021-10-01 16:38 ` kernel test robot
2021-09-30 18:11 ` [PATCH v1 20/38] arm64/sme: Implement support for TPIDR2 Mark Brown
2021-09-30 18:11 ` [PATCH v1 21/38] arm64/sme: Implement SVCR context switching Mark Brown
2021-10-11 12:15 ` Jonathan Cameron
2021-09-30 18:11 ` [PATCH v1 22/38] arm64/sme: Implement streaming SVE " Mark Brown
2021-09-30 18:11 ` [PATCH v1 23/38] arm64/sme: Implement ZA " Mark Brown
2021-10-11 12:27 ` Jonathan Cameron
2021-09-30 18:11 ` [PATCH v1 24/38] arm64/sme: Implement traps and syscall handling for SME Mark Brown
2021-10-11 12:37 ` Jonathan Cameron
2021-09-30 18:11 ` [PATCH v1 25/38] arm64/sme: Implement streaming SVE signal handling Mark Brown
2021-09-30 18:11 ` [PATCH v1 26/38] arm64/sme: Implement ZA " Mark Brown
2021-09-30 18:11 ` [PATCH v1 27/38] arm64/sme: Implement ptrace support for streaming mode SVE registers Mark Brown
2021-09-30 18:11 ` [PATCH v1 28/38] arm64/sme: Add ptrace support for ZA Mark Brown
2021-09-30 18:11 ` [PATCH v1 29/38] arm64/sme: Disable streaming mode and ZA when flushing CPU state Mark Brown
2021-09-30 18:11 ` [PATCH v1 30/38] arm64/sme: Save and restore streaming mode over EFI runtime calls Mark Brown
2021-09-30 18:11 ` [PATCH v1 31/38] arm64/sme: Provide Kconfig for SME Mark Brown
2021-09-30 18:11 ` [PATCH v1 32/38] kselftest/arm64: Add tests for TPIDR2 Mark Brown
2021-09-30 18:11 ` [PATCH v1 33/38] kselftest/arm64: Extend vector configuration API tests to cover SME Mark Brown
2021-09-30 18:11 ` [PATCH v1 34/38] kselftest/arm64: sme: Provide streaming mode SVE stress test Mark Brown
2021-09-30 18:11 ` [PATCH v1 35/38] kselftest/arm64: Add stress test for SME ZA context switching Mark Brown
2021-09-30 18:11 ` [PATCH v1 36/38] kselftest/arm64: signal: Add SME signal handling tests Mark Brown
2021-09-30 18:11 ` [PATCH v1 37/38] selftests: arm64: Add streaming SVE to SVE ptrace tests Mark Brown
2021-09-30 18:11 ` [PATCH v1 38/38] selftests: arm64: Add coverage for the ZA ptrace interface Mark Brown
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