Re: [Xen-devel] [PATCH 1/2] xen: Drop XEN_DOMCTL_suppress_spurious_page_faults

[Jan Beulich <jbeulich@suse.com>]

On 13.08.2019 12:53, Andrew Cooper wrote:
> This functionality is obsolete.  It was introduced by c/s 39407bed9c0 into
> Xend, but never exposed in libxl.

This is good enough a reason I think (hope), while ...

> While not explicitly limited to PV guests, this is PV-only by virtue of its
> position in the pagefault handler.
> 
> Looking though the XenServer templates, this was used to work around bugs in
> the 32bit RHEL/CentOS 4.{5..7} kernels (fixed in 4.8).  RHEL 4 as a major
> version when out if support in 2017.

... I wouldn't accept this as justification, since people are
free to use out-of-support software for as long as they wish.

> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Hypervisor parts
Reviewed-by: Jan Beulich <jbeulich@suse.com>
with one further suggestion:

> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -1452,20 +1452,6 @@ void do_page_fault(struct cpu_user_regs *regs)
>                 error_code, _p(addr));
>       }
>   
> -    if ( unlikely(current->domain->arch.suppress_spurious_page_faults) )
> -    {
> -        pf_type = spurious_page_fault(addr, regs);
> -        if ( (pf_type == smep_fault) || (pf_type == smap_fault))
> -        {
> -            printk(XENLOG_G_ERR "%pv fatal SM%cP violation\n",
> -                   current, (pf_type == smep_fault) ? 'E' : 'A');
> -
> -            domain_crash(current->domain);
> -        }
> -        if ( pf_type != real_fault )
> -            return;
> -    }

You may want to consider reducing pf_type's scope at the same
time.

Jan

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