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From: Auger Eric <eric.auger@redhat.com>
To: Christoffer Dall <cdall@linaro.org>
Cc: Andre Przywara <andre.przywara@arm.com>,
	eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, marc.zyngier@arm.com,
	peter.maydell@linaro.org, wanghaibin.wang@huawei.com,
	wu.wubin@huawei.com
Subject: Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER
Date: Sat, 14 Oct 2017 10:53:01 +0200	[thread overview]
Message-ID: <c5169f0d-3edb-11e2-6036-c5d076b1dbc8@redhat.com> (raw)
In-Reply-To: <20171013175446.GC17578@cbox>

Hi Christoffer,

On 13/10/2017 19:54, Christoffer Dall wrote:
> On Fri, Oct 13, 2017 at 01:54:34PM +0200, Auger Eric wrote:
>> Hi Christoffer,
>> On 13/10/2017 13:44, Christoffer Dall wrote:
>>> On Fri, Oct 06, 2017 at 05:29:02PM +0200, Auger Eric wrote:
>>>> Hi,
>>>>
>>>> On 06/10/2017 16:37, Andre Przywara wrote:
>>>>> Hi,
>>>>>
>>>>> On 27/09/17 14:28, Eric Auger wrote:
>>>>>> If the GITS_CBASER Size field is 0, which can correspond to a
>>>>>> reset value, the userspace fails to set the GITS_CREADR/CWRITER
>>>>>> offsets to 0. This failure is not justified.
>>>>>>
>>>>>> Let's allow this setting which can also correspond to a reset value.
>>>>>
>>>>> But the GITS_CBASER size field has a +1 encoding, so can never be 0, if
>>>>> I understand the manual (and ITS_CMD_BUFFER_SIZE) correctly.
>>>> Oh OK, you're. I missed that. I would have sworn I've seen that failure
>>>> but I must have misinterpreted it.
>>>>
>>>
>>> What is CWRITER is written to a brand new ITS before the CBASER is
>>> written?
>>>
>>> I don't see us initializing the cbaser field anywhere?
>> in vgic_its_create() its is allocated with kzalloc so its->cbaser is
>> initialized at this moment.
>>
> 
> Right, so it can be 0, and we still need your patch, contrary to Andre's
> comment.  Am I missing something?

No Andre is right, cbaser = 0 but ITS_CMD_BUFFER_SIZE(its->cbaser)
returns 4kB.

#define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)

So the check doesn't fail.

Thanks

Eric


> 
> Thanks,
> -Christoffer
> 

  reply	other threads:[~2017-10-14  8:53 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-27 13:28 [PATCH v2 00/10] vITS Migration fixes and reset Eric Auger
2017-09-27 13:28 ` [PATCH v2 01/10] KVM: arm/arm64: vgic-its: fix return value for restore Eric Auger
2017-10-06 14:37   ` Andre Przywara
2017-10-06 15:33     ` Auger Eric
2017-10-13 11:04   ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER Eric Auger
2017-10-06 14:37   ` Andre Przywara
2017-10-06 15:29     ` Auger Eric
2017-10-13 11:44       ` Christoffer Dall
2017-10-13 11:54         ` Auger Eric
2017-10-13 17:54           ` Christoffer Dall
2017-10-14  8:53             ` Auger Eric [this message]
2017-10-14 15:04               ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 03/10] KVM: arm/arm64: vgic-its: Improve error reporting on device table save Eric Auger
2017-10-06 14:38   ` Andre Przywara
2017-10-13 13:16   ` Christoffer Dall
2017-10-13 14:22     ` Auger Eric
2017-10-13 17:56       ` Christoffer Dall
2017-10-14  8:52         ` Auger Eric
2017-10-14 15:06           ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 04/10] KVM: arm/arm64: vgic-its: Check GITS_BASER Valid bit before saving tables Eric Auger
2017-10-06 14:38   ` Andre Przywara
2017-10-13 13:24   ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 05/10] KVM: arm/arm64: vgic-its: Check GITS_CBASER validity before processing commands Eric Auger
2017-10-06 14:38   ` Andre Przywara
2017-10-06 15:29     ` Auger Eric
2017-09-27 13:28 ` [PATCH v2 06/10] KVM: arm/arm64: vgic-its: Always attempt to save/restore device and collection tables Eric Auger
2017-10-06 14:38   ` Andre Przywara
2017-10-06 15:29     ` Auger Eric
2017-09-27 13:28 ` [PATCH v2 07/10] KVM: arm/arm64: vgic-its: new helper functions to free the caches Eric Auger
2017-10-13 13:35   ` Christoffer Dall
2017-10-13 14:37     ` Auger Eric
2017-10-21  9:02     ` Auger Eric
2017-10-21 14:34       ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 08/10] KVM: arm/arm64: vgic-its: free caches when GITS_BASER Valid bit is cleared Eric Auger
2017-10-13 15:19   ` Christoffer Dall
2017-10-13 15:34     ` Auger Eric
2017-10-13 17:59       ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 09/10] KVM: arm/arm64: Document KVM_DEV_ARM_ITS_CTRL_RESET Eric Auger
2017-10-12 10:57   ` Peter Maydell
2017-10-12 11:34     ` Auger Eric
2017-10-13 15:26   ` Christoffer Dall
2017-10-13 15:41     ` Auger Eric
2017-10-13 18:00       ` Christoffer Dall
2017-09-27 13:28 ` [PATCH v2 10/10] KVM: arm/arm64: vgic-its: Implement KVM_DEV_ARM_ITS_CTRL_RESET Eric Auger
2017-10-13 15:40   ` Christoffer Dall

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