linux-kernel - Re: [Xen-devel] [PATCH v2 4/8] xen: Use the correctly the Xen memory terminologies

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Message-ID: <55C20513.2070407@oracle.com>
Date:	Wed, 05 Aug 2015 08:44:03 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Julien Grall <julien.grall@...rix.com>,
	xen-devel@...ts.xenproject.org
CC:	linux-fbdev@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Jiri Slaby <jslaby@...e.com>,
	Russell King <linux@....linux.org.uk>,
	linux-scsi@...r.kernel.org, x86@...nel.org,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-input@...r.kernel.org,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	ian.campbell@...rix.com, stefano.stabellini@...citrix.com,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	Juergen Gross <jgross@...e.com>, Wei Liu <wei.liu2@...rix.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-kernel@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>, netdev@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	Roger Pau Monné <roger.pau@...rix.com>
Subject: Re: [Xen-devel] [PATCH v2 4/8] xen: Use the correctly the Xen memory
 terminologies

On 08/05/2015 08:33 AM, Julien Grall wrote:
> On 05/08/15 13:19, Boris Ostrovsky wrote:
>> On 08/05/2015 06:51 AM, Julien Grall wrote:
>>>>> diff --git a/drivers/video/fbdev/xen-fbfront.c
>>>>> b/drivers/video/fbdev/xen-fbfront.c
>>>>> index 09dc447..25e3cce 100644
>>>>> --- a/drivers/video/fbdev/xen-fbfront.c
>>>>> +++ b/drivers/video/fbdev/xen-fbfront.c
>>>>> @@ -539,7 +539,7 @@ static int xenfb_remove(struct xenbus_device *dev)
>>>>>       static unsigned long vmalloc_to_mfn(void *address)
>>>>>     {
>>>>> -    return pfn_to_mfn(vmalloc_to_pfn(address));
>>>>> +    return pfn_to_gfn(vmalloc_to_pfn(address));
>>>>>     }
>>>> Are you sure? This will return vmalloc_to_pfn(address)).
>>> I guess you mean vmalloc_to_mfn will return vmalloc_to_pfn?
>>>
>>> If so, it will be only the case on auto-translated case (because pfn ==
>>> gfn). In the case of PV, the mfn will be returned.
>> How will mfn be returned on PV when pfn_to_gfn() is an identity function?
>>
>> static inline unsigned long pfn_to_gfn(unsigned long pfn)
>>   {
>>       return pfn;
>>   }
> The identity function is only for ARM guest which are always
> auto-translated (arch/arm/include/asm/xen/page.h).
>
> The x86 version contains a check if the guest is auto-translated or not
> (arch/x86/include/asm/xen/page.):
>
> static inline unsigned long pfn_to_gfn(unsigned long pfn)
> {
>          if (xen_feature(XENFEAT_auto_translated_physmap))
>                  return pfn;
>          else
>                  return pfn_to_mfn(pfn);
> }

Of course --- I was looking at the top of the patch and didn't realize 
it was ARM changes. Sorry for the noise.

-boris
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