From: linux@roeck-us.net (Guenter Roeck)
To: linux-riscv@lists.infradead.org
Subject: [PATCH v3 1/2] RISC-V: Define sys_riscv_flush_icache when SMP=n
Date: Fri, 10 Aug 2018 11:47:15 -0700 [thread overview]
Message-ID: <20180810184715.GA11259@roeck-us.net> (raw)
In-Reply-To: <mhng-341b5b76-2cd6-41e3-859a-6b1d926ba770@palmer-si-x1c4>
On Fri, Aug 10, 2018 at 11:27:37AM -0700, Palmer Dabbelt wrote:
> On Fri, 10 Aug 2018 01:38:04 PDT (-0700), Christoph Hellwig wrote:
> >On Thu, Aug 09, 2018 at 03:19:51PM -0700, Palmer Dabbelt wrote:
> >>This would be necessary to make non-SMP builds work, but there is
> >>another error in the implementation of our syscall linkage that actually
> >>just causes sys_riscv_flush_icache to never build. I've build tested
> >>this on allnoconfig and allnoconfig+SMP=y, as well as defconfig like
> >>normal.
> >
> >Would't it make sense to use COND_SYSCALL to stub out the syscall
> >for !SMP builds?
>
> I'm not sure. We can implement the syscall fine in !SMP, it's just that the
> vDSO is expected to always eat these calls because in non-SMP mode you can
> do a global fence.i by just doing a local fence.i (there's only one hart).
>
> The original rationale behind not having the syscall in non-SMP mode was to
> limit the user ABI, but on looking again that seems like it's just a bit of
> extra complexity that doesn't help anything. It's already been demonstrated
Doesn't this mean that some userspace code will only run if the kernel was
compiled for SMP ? I always thought that was unacceptable.
Guenter
> that nothing is checking the error because it's been silently slipping past
> userspace for six months, so the extra complexity seems like it'll just
> cause someone else to have to chase the bug in the future.
>
> But I'm really OK either way. Is there a precedent for what to do here?
next prev parent reply other threads:[~2018-08-10 18:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-09 22:19 RISC-V: Don't use a global include guard for uapi/asm/syscalls Palmer Dabbelt
2018-08-09 22:19 ` [PATCH v3 1/2] RISC-V: Define sys_riscv_flush_icache when SMP=n Palmer Dabbelt
2018-08-10 8:38 ` Christoph Hellwig
2018-08-10 18:27 ` Palmer Dabbelt
2018-08-10 18:47 ` Guenter Roeck [this message]
2018-08-10 20:55 ` Palmer Dabbelt
2018-08-14 13:35 ` Christoph Hellwig
2018-08-10 14:07 ` Guenter Roeck
2018-08-14 13:39 ` Christoph Hellwig
2018-08-20 23:30 ` Palmer Dabbelt
2018-08-09 22:19 ` [PATCH v3 2/2] RISC-V: Don't use a global include guard for uapi/asm/syscalls.h Palmer Dabbelt
2018-08-10 14:07 ` Guenter Roeck
2018-08-14 13:40 ` Christoph Hellwig
2018-08-20 23:30 ` Palmer Dabbelt
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