[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH V7 2/2] xen/gnttab: Store frame GFN in struct page_info on Arm
- To: Julien Grall <julien@xxxxxxx>, Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 11 Oct 2022 15:28:26 +0200
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=suse.com; dmarc=pass action=none header.from=suse.com; dkim=pass header.d=suse.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=3KryHIzf/Kz8GVsaPjcvhzBMiBaQ5ofEduiQuZ9eTRY=; b=XxtxWfr26x10Ay4R+3/pmWn6j01GrzOVYc4W8qmW8JW36FUNkP1CGP2f2cV5HJvFNuHCPGdbDLJ9uJIP3grZccDm+nk1lOT3wT8Wo3seomTTo/u4dI7r/KPyYO1sf+x4ZEweSeHozN4abVZhmeI4Y2Xm9fs0JUPsKiQ977ddEczLO2+hPoc2bfJJZr6Xo8DggrNsWzaMyuvXdZbVCq23GSfdZrpU7vyIgKfX+7QT60K4WmZKPpsxX9Cid9FrASCvLP44F/FvHBUMm3zt02CKaDtgohqrHPe3KRpDYTsB127l08Gtrtc22aVYR5tWR8trkKSXYOHfV6iLzHHllkzDFg==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=FpBP5ev52dLnuZfK2I8HhQ1BdYMGmHVayjjR22qTGn6Y13jc0zdB9z9lS4b5N6MexgpV6glO9leN1oLANcWOMjK7+pEtjERd9gRe8CpkS4r5OLm8Il4MyV8zlqEWoEXUYMae5lT1ksEWmc4dAijllroX7i7QK1fFBnlm4fI2wlfQscPUUU61eBLZ5iajoOmX88gfjMcLCXGRaVK9HrlFrqqJu648SMZoD1a4cqktOVwZxXm6se4vLxB8H2xM99rTkhjvuYjnzkKH1guIN/KknkQfg7REXDiLzZrRak3A2UZioaTYgC4B2vm18XyvIFhpQOVDCvnNCuAt5NCFQa+Nyw==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=suse.com;
- Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Henry Wang <Henry.Wang@xxxxxxx>
- Delivery-date: Tue, 11 Oct 2022 13:28:36 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11.10.2022 15:01, Julien Grall wrote:
> Hi Jan,
>
> On 11/10/2022 12:59, Jan Beulich wrote:
>> On 16.07.2022 16:56, Oleksandr Tyshchenko wrote:
>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>
>>> Rework Arm implementation to store grant table frame GFN
>>> in struct page_info directly instead of keeping it in
>>> standalone status/shared arrays. This patch is based on
>>> the assumption that a grant table page is a xenheap page.
>>>
>>> To cover 64-bit/40-bit IPA on Arm64/Arm32 we need the space
>>> to hold 52-bit/28-bit + extra bit value respectively. In order
>>> to not grow the size of struct page_info borrow the required
>>> amount of bits from type_info's count portion which current
>>> context won't suffer (currently only 1 bit is used on Arm).
>>
>> I'm afraid this isn't true: There's no requirement for a guest to pass
>> all different GFNs to VCPUOP_register_vcpu_info, yet map_vcpu_info()
>> tries to obtain a reference for every vCPU.
>
> AFAIU, this would be a reference of the **count_info** not **type_info**
> (which BTW will never be incremented on Arm because we have no type
> support).
I should have said "obtain a writable type reference".
> The commit message is only referring to the 'type_info's count'. So...
>
>> With my adding of GFN
>> (really gaddr) based registration of the runstate area (already
>> looking towards 4.18) the maximum possible count is to further grow.
>
> ... I am not sure which problem you are referring too.
Wow - a mere stub (but not inline) function to make the build happy.
Then why is the description talking about one bit that's needed on
Arm?
Jan
|
