linux-kernel - Re: [PATCH v3 05/19] vdpa_sim: remove the limit of IOTLB entries

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Message-ID: <0333484d-7fa1-fc88-7e22-14492e994b72@redhat.com>
Date:   Thu, 10 Dec 2020 12:03:03 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, Oren Duer <oren@...dia.com>,
        Laurent Vivier <lvivier@...hat.com>,
        linux-kernel@...r.kernel.org, Max Gurtovoy <mgurtovoy@...dia.com>,
        Shahaf Shuler <shahafs@...dia.com>, Eli Cohen <elic@...dia.com>
Subject: Re: [PATCH v3 05/19] vdpa_sim: remove the limit of IOTLB entries


On 2020/12/9 下午6:58, Stefano Garzarella wrote:
> On Mon, Dec 07, 2020 at 12:00:07PM +0800, Jason Wang wrote:
>>
>> On 2020/12/4 上午1:04, Stefano Garzarella wrote:
>>> The simulated devices can support multiple queues, so this limit
>>> should be defined according to the number of queues supported by
>>> the device.
>>>
>>> Since we are in a simulator, let's simply remove that limit.
>>>
>>> Suggested-by: Jason Wang <jasowang@...hat.com>
>>> Acked-by: Jason Wang <jasowang@...hat.com>
>>> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>>
>>
>> Rethink about this, since simulator can be used by VM, so the 
>> allocation is actually guest trigger-able when vIOMMU is enabled.
>>
>> This means we need a limit somehow, (e.g I remember swiotlb is about 
>> 64MB by default). Or having a module parameter for this.
>>
>> Btw, have you met any issue when using 2048, I guess it can happen 
>> when we run several processes in parallel?
>>
>
> No, I didn't try with the limit.
> This came from the reviews to Max's patches.
>
> Anyway I can add a module parameter to control that limit, do you 
> think is better to set a limit per queue (the parameter per number of 
> queues), or just a value for the entire device?


Per-device should be ok.

Thanks


>
> Thanks,
> Stefano
>