From: Andrea Parri <parri.andrea@gmail.com> To: Guo Ren <guoren@kernel.org> Cc: Jisheng Zhang <jszhang@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: fix race when vmap stack overflow Date: Fri, 21 Oct 2022 10:36:35 +0200 [thread overview] Message-ID: <Y1JaE/ot91Z0KXuC@andrea> (raw) In-Reply-To: <CAJF2gTRAEX_jQ_w5H05dyafZzHq+P5j05TJ=C+v+OL__GQam4A@mail.gmail.com> > > > + atomic_set_release(&spin_shadow_stack, 0); > > > > Have not really looked the details: should there be a matching acquire? > > I use atomic_set_release here, because I need earlier memory > operations finished to make sure the sp is ready then set the spin > flag. > > The following memory operations order is not important, because we > just care about sp value. > > Also, we use relax amoswap before, because sp has naturelly > dependency. But giving them RCsc is okay here, because we don't care > about performance here. Thanks for the clarification. I'm not really suggesting to add unneeded synchronization, even more so in local/private constructs as in this case. It just felt odd to see the release without a pairing acquire, so I asked. ;-) Thanks, Andrea > eg: > handle_kernel_stack_overflow: > +1: la sp, spin_shadow_stack > + amoswap.w.aqrl sp, sp, (sp) > + bnez sp, 1b > + > .... > + smp_store_release(&spin_shadow_stack, 0); > + smp_mb();
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From: Andrea Parri <parri.andrea@gmail.com> To: Guo Ren <guoren@kernel.org> Cc: Jisheng Zhang <jszhang@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: fix race when vmap stack overflow Date: Fri, 21 Oct 2022 10:36:35 +0200 [thread overview] Message-ID: <Y1JaE/ot91Z0KXuC@andrea> (raw) In-Reply-To: <CAJF2gTRAEX_jQ_w5H05dyafZzHq+P5j05TJ=C+v+OL__GQam4A@mail.gmail.com> > > > + atomic_set_release(&spin_shadow_stack, 0); > > > > Have not really looked the details: should there be a matching acquire? > > I use atomic_set_release here, because I need earlier memory > operations finished to make sure the sp is ready then set the spin > flag. > > The following memory operations order is not important, because we > just care about sp value. > > Also, we use relax amoswap before, because sp has naturelly > dependency. But giving them RCsc is okay here, because we don't care > about performance here. Thanks for the clarification. I'm not really suggesting to add unneeded synchronization, even more so in local/private constructs as in this case. It just felt odd to see the release without a pairing acquire, so I asked. ;-) Thanks, Andrea > eg: > handle_kernel_stack_overflow: > +1: la sp, spin_shadow_stack > + amoswap.w.aqrl sp, sp, (sp) > + bnez sp, 1b > + > .... > + smp_store_release(&spin_shadow_stack, 0); > + smp_mb(); _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2022-10-21 8:37 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-19 15:47 [PATCH] riscv: fix race when vmap stack overflow Jisheng Zhang 2022-10-19 15:47 ` Jisheng Zhang 2022-10-20 1:02 ` Guo Ren 2022-10-20 1:02 ` Guo Ren 2022-10-20 2:16 ` Guo Ren 2022-10-20 2:16 ` Guo Ren 2022-10-20 14:38 ` Jisheng Zhang 2022-10-20 14:38 ` Jisheng Zhang 2022-10-21 0:35 ` Guo Ren 2022-10-21 0:35 ` Guo Ren 2022-10-20 23:26 ` Andrea Parri 2022-10-20 23:26 ` Andrea Parri 2022-10-21 1:11 ` Guo Ren 2022-10-21 1:11 ` Guo Ren 2022-10-21 8:36 ` Andrea Parri [this message] 2022-10-21 8:36 ` Andrea Parri 2022-10-21 12:08 ` Tong Tiangen 2022-10-21 12:08 ` Tong Tiangen 2022-10-21 13:22 ` Andrea Parri 2022-10-21 13:22 ` Andrea Parri 2022-10-21 13:46 ` Tong Tiangen 2022-10-21 13:46 ` Tong Tiangen 2022-10-21 14:41 ` Guo Ren 2022-10-21 14:41 ` Guo Ren 2022-10-21 15:17 ` Tong Tiangen 2022-10-21 15:17 ` Tong Tiangen 2022-10-21 14:35 ` Guo Ren 2022-10-21 14:35 ` Guo Ren
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