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Re: [PATCH v3 15/34] xen/riscv: introduce atomic.h
- To: Oleksii <oleksii.kurochko@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 23 Jan 2024 11:30:15 +0100
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- Cc: Bobby Eshleman <bobbyeshleman@xxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 23 Jan 2024 10:30:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 23.01.2024 11:21, Oleksii wrote:
> On Mon, 2024-01-22 at 17:56 +0100, Jan Beulich wrote:
>> On 22.12.2023 16:12, Oleksii Kurochko wrote:
>>> --- /dev/null
>>> +++ b/xen/arch/riscv/include/asm/fence.h
>>> @@ -0,0 +1,13 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>> +#ifndef _ASM_RISCV_FENCE_H
>>> +#define _ASM_RISCV_FENCE_H
>>> +
>>> +#ifdef CONFIG_SMP
>>> +#define RISCV_ACQUIRE_BARRIER "\tfence r , rw\n"
>>> +#define RISCV_RELEASE_BARRIER "\tfence rw, w\n"
>>> +#else
>>> +#define RISCV_ACQUIRE_BARRIER
>>> +#define RISCV_RELEASE_BARRIER
>>> +#endif
>>
>> Do you really care about the !SMP case? On x86 at least we stopped
>> special-
>> casing that configuration many years ago (the few cases where for
>> typically
>> build reasons it matters, using CONFIG_NR_CPUS is sufficient). If you
>> care
>> about it, there needs to be somewhere you actually #define
>> CONFIG_SMP.
> Can't we use instead of CONFIG_SMP - CONFIG_NR_CPUS?
You can. Question is whether there's a point in doing so. Do you
expect people to actually want to run Xen on single-CPU systems?
They're generally not overly well suited for virtualization ...
Jan
|
