linux-kernel - Re: [PATCH 1/3] arm/arm64/xen: use C inlines for privcmd

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Date:   Fri, 29 Nov 2019 15:05:11 +0000
From:   Julien Grall <julien@....org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>, jmorris@...ei.org,
        sashal@...nel.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, will@...nel.org, steve.capper@....com,
        linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        james.morse@....com, vladimir.murzin@....com, mark.rutland@....com,
        tglx@...utronix.de, gregkh@...uxfoundation.org,
        allison@...utok.net, info@...ux.net, alexios.zavras@...el.com,
        sstabellini@...nel.org, boris.ostrovsky@...cle.com,
        jgross@...e.com, stefan@...er.ch, yamada.masahiro@...ionext.com,
        xen-devel@...ts.xenproject.org, linux@...linux.org.uk
Subject: Re: [PATCH 1/3] arm/arm64/xen: use C inlines for privcmd_call

Hi,

On 27/11/2019 18:44, Pavel Tatashin wrote:
> diff --git a/arch/arm64/include/asm/xen/hypercall.h b/arch/arm64/include/asm/xen/hypercall.h
> index 3522cbaed316..1a74fb28607f 100644
> --- a/arch/arm64/include/asm/xen/hypercall.h
> +++ b/arch/arm64/include/asm/xen/hypercall.h
> @@ -1 +1,29 @@
> +#ifndef _ASM_ARM64_XEN_HYPERCALL_H
> +#define _ASM_ARM64_XEN_HYPERCALL_H
>   #include <xen/arm/hypercall.h>
> +#include <linux/uaccess.h>
> +
> +static inline long privcmd_call(unsigned int call, unsigned long a1,
> +				unsigned long a2, unsigned long a3,
> +				unsigned long a4, unsigned long a5)

I realize that privcmd_call is the only hypercall using Software PAN at 
the moment. However, dm_op needs the same as hypercall will be issued 
from userspace as well.

So I was wondering whether we should create a generic function (e.g. 
do_xen_hypercall() or do_xen_user_hypercall()) to cover the two hypercalls?

> diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
> index b40485e54d80..624c8ad7e42a 100644
> --- a/include/xen/arm/hypercall.h
> +++ b/include/xen/arm/hypercall.h
> @@ -30,8 +30,8 @@
>    * IN THE SOFTWARE.
>    */
>   
> -#ifndef _ASM_ARM_XEN_HYPERCALL_H
> -#define _ASM_ARM_XEN_HYPERCALL_H
> +#ifndef _ARM_XEN_HYPERCALL_H
> +#define _ARM_XEN_HYPERCALL_H

This change feels a bit out of context. Could you split it in a separate 
patch?

>   
>   #include <linux/bug.h>
>   
> @@ -41,9 +41,9 @@
>   
>   struct xen_dm_op_buf;
>   
> -long privcmd_call(unsigned call, unsigned long a1,
> -		unsigned long a2, unsigned long a3,
> -		unsigned long a4, unsigned long a5);
> +long arch_privcmd_call(unsigned int call, unsigned long a1,
> +		       unsigned long a2, unsigned long a3,
> +		       unsigned long a4, unsigned long a5);
>   int HYPERVISOR_xen_version(int cmd, void *arg);
>   int HYPERVISOR_console_io(int cmd, int count, char *str);
>   int HYPERVISOR_grant_table_op(unsigned int cmd, void *uop, unsigned int count);
> @@ -88,4 +88,4 @@ MULTI_mmu_update(struct multicall_entry *mcl, struct mmu_update *req,
>   	BUG();
>   }
>   
> -#endif /* _ASM_ARM_XEN_HYPERCALL_H */
> +#endif /* _ARM_XEN_HYPERCALL_H */
> 

Cheers,

-- 
Julien Grall