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From: Jeff Law <jlaw@ventanamicro.com>
To: Richard Henderson <richard.henderson@linaro.org>,
	Vineet Gupta <vineetg@rivosinc.com>,
	Kito Cheng <kito.cheng@sifive.com>
Cc: "Philipp Tomsich" <philipp.tomsich@vrull.eu>,
	"Andy Chiu" <andy.chiu@sifive.com>,
	"Vincent Chen" <vincent.chen@sifive.com>,
	"Florian Weimer" <fweimer@redhat.com>,
	"Rich Felker" <dalias@libc.org>,
	"Andrew Waterman" <andrew@sifive.com>,
	"Palmer Dabbelt" <palmer@rivosinc.com>,
	"Christoph Müllner" <christoph.muellner@vrull.eu>,
	davidlt@rivosinc.com, "Arnd Bergmann" <arnd@arndb.de>,
	"Björn Töpel" <bjorn@kernel.org>,
	"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
	"Greentime Hu" <greentime.hu@sifive.com>,
	"Aaron Durbin" <adurbin@rivosinc.com>,
	"Andrew de los Reyes" <adlr@rivosinc.com>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	"GNU C Library" <libc-alpha@sourceware.org>
Subject: Re: Auto-enabling V unit and/or use of elf attributes (was Re: Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break)
Date: Tue, 10 Jan 2023 21:28:16 -0700	[thread overview]
Message-ID: <119da65f-e976-f382-3fe1-1585be738352@ventanamicro.com> (raw)
In-Reply-To: <3923eeee-e4dc-0911-40bf-84c34aee962d@linaro.org>



On 1/10/23 18:22, Richard Henderson wrote:
> On 1/10/23 10:07, Vineet Gupta wrote:
>> Yes bulk of glibc might not have vector code, but those V ifunc 
>> routines do and IMO this information needs to be recorded somewhere in 
>> the elf. Case in point being the current issue with how to enable V 
>> unit. Community wants a per-process enable, using an explicit prctl 
>> from userspace (since RV doesn't have fault-on-first use hardware 
>> mechanism unlike some of the other arches). But how does the glibc 
>> loader know to invoke prctl. We can't just rely on user env 
>> GLIBC_TUNABLE etc since that might not be accurate. It needs somethign 
>> concrete which IMO can come from elf attributes. If not, do you have 
>> suggestions on how to solve this issue ?
> 
> Why not just fault on first use to enable?  That's vastly less 
> complicated than trying to plumb anything through elf resulting in a prctl.
Well, the answer is in Vineet's paragraph -- the hardware apparently 
doesn't have fault-on-first-use which is mighty unfortunate.

Jeff

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  reply	other threads:[~2023-01-11  4:28 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1631497278-29829-1-git-send-email-vincent.chen@sifive.com>
     [not found] ` <1631497278-29829-3-git-send-email-vincent.chen@sifive.com>
     [not found]   ` <871r5sd1zq.fsf@oldenburg.str.redhat.com>
     [not found]     ` <20210913135247.GL13220@brightrain.aerifal.cx>
     [not found]       ` <CABvJ_xjGZ3S0oAkT08x4DToQFdcUH06omk2OTT1EHDZRJ-2wKg@mail.gmail.com>
     [not found]         ` <87sfy5ndid.fsf@oldenburg.str.redhat.com>
     [not found]           ` <CABvJ_xjSREsdemJkCJMGSx+09jrNoSbXCwuxF0zEQmZtHrWMvg@mail.gmail.com>
     [not found]             ` <d613968f-0fae-1994-3bee-fb10765167c3@rivosinc.com>
2022-12-20 20:05               ` Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break Vineet Gupta
2022-12-21 15:53                 ` Vincent Chen
2022-12-21 19:45                   ` Vineet Gupta
2022-12-21 19:52                     ` Vineet Gupta
2022-12-22  3:37                       ` Vincent Chen
2022-12-22 19:25                         ` Vineet Gupta
2022-12-23  2:27                           ` Vincent Chen
2022-12-23 19:42                             ` Vineet Gupta
2022-12-22  5:32                       ` Richard Henderson
2022-12-22 18:33                         ` Andy Chiu
2022-12-22 20:27                           ` Vineet Gupta
2022-12-28 10:53                             ` Andy Chiu
2023-01-03 19:17                               ` Vineet Gupta
2023-01-04 16:34                                 ` Andy Chiu
2023-01-04 20:46                                   ` Vineet Gupta
2023-01-04 21:29                                     ` Philipp Tomsich
2023-01-04 21:37                                       ` Andrew Waterman
2023-01-04 22:43                                       ` Vineet Gupta
2023-01-09 13:33                                         ` Kito Cheng
2023-01-09 19:16                                           ` Vineet Gupta
2023-01-10 13:21                                             ` Kito Cheng
2023-01-10 18:07                                               ` Auto-enabling V unit and/or use of elf attributes (was Re: Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break) Vineet Gupta
2023-01-11  1:22                                                 ` Richard Henderson
2023-01-11  4:28                                                   ` Jeff Law [this message]
2023-01-11  4:57                                                     ` Richard Henderson
2023-01-11  5:07                                                       ` Jeff Law
2023-01-11  6:00                                                         ` Andy Chiu
2023-01-11  6:20                                                           ` Jeff Law
2023-01-11  9:28                                                             ` Andy Chiu
2023-01-11 12:13                                                               ` Andy Chiu
2023-01-23 12:17                                                                 ` Conor Dooley
2023-01-23 13:29                                                                   ` Andy Chiu
2023-01-11  5:05                                                   ` Anup Patel
2023-01-11  5:23                                                   ` Richard Henderson
2022-12-22 22:33                           ` Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break Richard Henderson
2022-12-22 23:47                           ` Conor Dooley
2022-12-22 23:58                             ` Vineet Gupta
2022-12-22 20:30                         ` Vineet Gupta
2022-12-22 21:38                           ` Andrew Waterman
2022-12-22  1:50                     ` Vincent Chen
2022-12-22  5:34                     ` Richard Henderson

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