From: Richard Henderson <richard.henderson@linaro.org>
To: "Vineet Gupta" <vineetg@rivosinc.com>,
"Florian Weimer" <fweimer@redhat.com>,
"Björn Töpel" <bjorn@kernel.org>
Cc: Darius Rad <darius@bluespec.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Andrew Waterman <andrew@sifive.com>,
stillson@rivosinc.com, Paul Walmsley <paul.walmsley@sifive.com>,
anup@brainfault.org, atishp@atishpatra.org, guoren@kernel.org,
Conor Dooley <conor.dooley@microchip.com>,
greentime.hu@sifive.com, vincent.chen@sifive.com,
andy.chiu@sifive.com, arnd@kernel.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
libc-alpha@sourceware.org, christoph.muellner@vrull.eu,
Aaron Durbin <adurbin@rivosinc.com>,
linux@rivosinc.com
Subject: Re: RISCV Vector unit disabled by default for new task (was Re: [PATCH v12 17/17] riscv: prctl to enable vector commands)
Date: Thu, 15 Dec 2022 11:56:12 -0800 [thread overview]
Message-ID: <37dbef55-fd78-91db-33fb-ca1691fe1cc6@linaro.org> (raw)
In-Reply-To: <15d902d0-4492-f828-7147-164319d741f9@rivosinc.com>
On 12/15/22 10:57, Vineet Gupta wrote:
>> The other thing of note for SVE is that, with the default function ABI all of the SVE
>> state is call-clobbered, which allows the kernel to drop instead of save state across
>> system calls. (There is a separate vector function call ABI when SVE types are used.)
>
> For the RV psABI, it is similar - all V regs are caller-saved/call-clobbered [1] and
> syscalls are not required to preserve V regs [2]
> However last I checked ARM documentation the ABI doc seemed to suggest that some (parts)
> of the SVE regs are callee-saved [3]
As Pinski mentioned, just some low bits that overlap with scalar fp state; the high bits
and the predicate registers gets zeroed when re-enabling.
>> So while strcpy may enable SVE for the thread, the next syscall may disable it again.
>
> Next syscall could trash them, but will it disable SVE ?
Yes. See fp_user_discard() in arch/arm64/kernel/syscall.c.
r~
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next prev parent reply other threads:[~2022-12-15 19:56 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 21:43 [PATCH v12 01/17] riscv: Rename __switch_to_aux -> fpu Chris Stillson
2022-09-21 21:43 ` [PATCH v12 02/17] riscv: Extending cpufeature.c to detect V-extension Chris Stillson
[not found] ` <4b6e20fb-d013-0a09-0b74-b6c46e045af3@rivosinc.com>
[not found] ` <CAJF2gTSPoKu_owEb6+MLhAgK5nz2FTRDkTn4qfXF4KyA-XTwvw@mail.gmail.com>
[not found] ` <CAJF2gTT_z96V3kjPtr9hpTq8XRn0x=91wFNPYFFdetAA2u-01Q@mail.gmail.com>
2022-11-04 9:13 ` Conor.Dooley
2022-11-04 18:04 ` Vineet Gupta
2022-09-21 21:43 ` [PATCH v12 03/17] riscv: Add new csr defines related to vector extension Chris Stillson
2023-01-23 11:24 ` Heiko Stübner
2022-09-21 21:43 ` [PATCH v12 04/17] riscv: Add vector feature to compile Chris Stillson
2022-11-07 17:21 ` Björn Töpel
2022-11-08 0:04 ` Vineet Gupta
2022-11-08 7:56 ` Conor Dooley
2022-11-08 17:17 ` Vineet Gupta
2022-11-08 17:22 ` Conor Dooley
2022-11-13 16:16 ` Conor.Dooley
2022-11-15 17:38 ` Vineet Gupta
2022-11-15 22:17 ` Conor Dooley
2022-12-15 0:40 ` Atish Patra
2022-09-21 21:43 ` [PATCH v12 05/17] riscv: Add has_vector/riscv_vsize to save vector features Chris Stillson
2022-09-22 4:23 ` Samuel Holland
2022-09-23 16:27 ` Chris Stillson
2022-09-24 18:01 ` Conor Dooley
2022-11-04 4:10 ` Vineet Gupta
2022-11-04 4:33 ` Vineet Gupta
2022-09-21 21:43 ` [PATCH v12 06/17] riscv: Reset vector register Chris Stillson
2022-11-04 5:01 ` Vineet Gupta
2022-11-04 8:45 ` Guo Ren
2023-01-20 12:20 ` Heiko Stübner
2022-09-21 21:43 ` [PATCH v12 07/17] riscv: Add vector struct and assembler definitions Chris Stillson
2022-11-04 5:13 ` Vineet Gupta
2022-09-21 21:43 ` [PATCH v12 08/17] riscv: Add task switch support for vector Chris Stillson
2022-11-04 22:08 ` Vineet Gupta
2022-09-21 21:43 ` [PATCH v12 09/17] riscv: Add ptrace vector support Chris Stillson
2022-11-08 1:38 ` Vineet Gupta
2022-11-14 20:01 ` Arnd Bergmann
2022-09-21 21:43 ` [PATCH v12 10/17] riscv: Add sigcontext save/restore for vector Chris Stillson
2022-11-09 1:27 ` Vineet Gupta
2022-09-21 21:43 ` [PATCH v12 11/17] riscv: signal: Report signal frame size to userspace via auxv Chris Stillson
2022-09-21 21:43 ` [PATCH v12 12/17] riscv: Add support for kernel mode vector Chris Stillson
2022-09-21 21:43 ` [PATCH v12 13/17] riscv: Add vector extension XOR implementation Chris Stillson
2022-09-21 21:43 ` [PATCH v12 14/17] riscv: Fix a kernel panic issue if $s2 is set to a specific value before entering Linux Chris Stillson
2022-09-21 21:43 ` [PATCH v12 15/17] riscv: Add V extension to KVM ISA allow list Chris Stillson
2022-09-21 21:43 ` [PATCH v12 16/17] riscv: KVM: Add vector lazy save/restore support Chris Stillson
2022-09-21 21:43 ` [PATCH v12 17/17] riscv: prctl to enable vector commands Chris Stillson
2022-12-09 5:16 ` RISCV Vector unit disabled by default for new task (was Re: [PATCH v12 17/17] riscv: prctl to enable vector commands) Vineet Gupta
2022-12-09 6:27 ` Palmer Dabbelt
2022-12-09 7:42 ` Andrew Waterman
2022-12-09 10:02 ` Florian Weimer
2022-12-09 12:21 ` Darius Rad
2022-12-09 12:32 ` Florian Weimer
2022-12-09 12:42 ` Darius Rad
2022-12-09 13:04 ` Florian Weimer
2022-12-09 17:21 ` Palmer Dabbelt
2022-12-09 19:42 ` Vineet Gupta
2022-12-09 19:58 ` Andrew Waterman
2022-12-13 16:43 ` Darius Rad
2022-12-14 20:07 ` Vineet Gupta
2022-12-14 23:13 ` Samuel Holland
2022-12-15 2:09 ` Darius Rad
2022-12-15 11:48 ` Björn Töpel
2022-12-15 12:28 ` Florian Weimer
2022-12-15 15:33 ` Richard Henderson
2022-12-15 18:57 ` Vineet Gupta
2022-12-15 18:59 ` Andrew Pinski
2022-12-15 19:01 ` Andrew Pinski
2022-12-15 19:56 ` Richard Henderson [this message]
2022-12-09 13:58 ` Icenowy Zheng
2023-01-23 11:20 ` [PATCH v12 01/17] riscv: Rename __switch_to_aux -> fpu Heiko Stübner
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