Re: [PATCH v2 08/15] xen/asm-generic: introduce generic header percpu.h

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Thu, 2023-11-16 at 08:36 +0100, Jan Beulich wrote:
> On 10.11.2023 17:30, Oleksii Kurochko wrote:
> > --- /dev/null
> > +++ b/xen/include/asm-generic/percpu.h
> > @@ -0,0 +1,35 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +#ifndef __ASM_GENERIC_PERCPU_H__
> > +#define __ASM_GENERIC_PERCPU_H__
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#include <xen/types.h>
> > +
> > +extern char __per_cpu_start[], __per_cpu_data_end[];
> 
> Can we go one tiny step beyond what Arm presently has and make the
> latter of the two const?
I am not sure I think we will have compilation issue with the following
code in Arm and x86 because of [-Werror=discarded-qualifiers]:

static void cf_check _free_percpu_area(struct rcu_head *head)
{
    struct free_info *info = container_of(head, struct free_info, rcu);
    unsigned int cpu = info->cpu;
    char *p = __per_cpu_start + __per_cpu_offset[cpu];

    free_xenheap_pages(p, PERCPU_ORDER);
    __per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
}

I guess cast can help.


~ Oleksii