linux-kernel - Re: [Xen-devel] [RFC v3 2/2] x86/xen: allow privcmd hypercalls to be preempted

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Message-ID: <54C15E20.8090201@linaro.org>
Date:	Thu, 22 Jan 2015 20:31:28 +0000
From:	Julien Grall <julien.grall@...aro.org>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
CC:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	david.vrabel@...rix.com, konrad.wilk@...cle.com,
	boris.ostrovsky@...cle.com, xen-devel@...ts.xenproject.org,
	kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...hat.com>,
	Jan Beulich <JBeulich@...e.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [Xen-devel] [RFC v3 2/2] x86/xen: allow privcmd hypercalls to
 be preempted

On 22/01/15 18:56, Luis R. Rodriguez wrote:
> On Thu, Jan 22, 2015 at 01:10:49PM +0000, Julien Grall wrote:
>> Hi Luis,
>>
>> On 22/01/15 02:17, Luis R. Rodriguez wrote:
>>> diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
>>> index b4bca2d..23c526b 100644
>>> --- a/drivers/xen/events/events_base.c
>>> +++ b/drivers/xen/events/events_base.c
>>> @@ -32,6 +32,8 @@
>>>  #include <linux/slab.h>
>>>  #include <linux/irqnr.h>
>>>  #include <linux/pci.h>
>>> +#include <linux/sched.h>
>>> +#include <linux/kprobes.h>
>>>  
>>>  #ifdef CONFIG_X86
>>>  #include <asm/desc.h>
>>> @@ -1243,6 +1245,17 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
>>>  	set_irq_regs(old_regs);
>>>  }
>>>  
>>> +notrace void xen_end_upcall(struct pt_regs *regs)
>>> +{
>>> +	if (!xen_is_preemptible_hypercall(regs) ||
>>
>> I don't see any definition of xen_is_preemptible_hypercall for ARM32/ARM64.
>>
>> As this function is called from the generic code, you have at least to
>> stub this function for those architectures.
> 
> Will add as:
> 
> diff --git a/arch/arm/include/asm/xen/hypercall.h b/arch/arm/include/asm/xen/hypercall.h
> index 712b50e..4fc8395 100644
> --- a/arch/arm/include/asm/xen/hypercall.h
> +++ b/arch/arm/include/asm/xen/hypercall.h
> @@ -74,4 +74,9 @@ MULTI_mmu_update(struct multicall_entry *mcl, struct mmu_update *req,
>  	BUG();
>  }
>  
> +static inline bool xen_is_preemptible_hypercall(struct pt_regs *regs)
> +{
> +	return false;
> +}
> +
>  #endif /* _ASM_ARM_XEN_HYPERCALL_H */
> 
> This will cover both arm and arm64 as arm64 includes the arm header.

I'm fine with this solution.

Regards,

-- 
Julien Grall
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