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Subject: Re: [RFC] virtio-mem: virtio_mem_init: Access bb_size just in BBM
 mode
From:   teawater <teawaterz@linux.alibaba.com>
In-Reply-To: <7fd8bf39-642d-1cdf-bc5d-c19630045013@redhat.com>
Date:   Tue, 15 Jun 2021 15:57:17 +0800
Cc:     Hui Zhu <teawater@gmail.com>, mst@redhat.com, jasowang@redhat.com,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
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Message-Id: <E11CAA85-B9A5-4D6F-85C6-505AFEFA9A7E@linux.alibaba.com>
References: <20210615065948.23493-1-teawater@gmail.com>
 <7fd8bf39-642d-1cdf-bc5d-c19630045013@redhat.com>
To:     David Hildenbrand <david@redhat.com>
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> 2021年6月15日 15:43，David Hildenbrand <david@redhat.com> 写道：
> 
> On 15.06.21 08:59, Hui Zhu wrote:
>> From: Hui Zhu <teawaterz@linux.alibaba.com>
>> /* In BBM, we also want at least two big blocks. */
>> vm->offline_threshold = max_t(uint64_t, 2 * vm->bbm.bb_size,
>> 			      vm->offline_threshold);
>> This line does not modify vm->offline_threshold depending on the data in
>> vm->sbm that shares this address is 0 in SBM mode.
>> I think it might be difficult to make sure when we change this in the
>> future.
>> This commit adds an if to make sure that this line just be executed in
>> BBM mode.
>> Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
>> ---
>>  drivers/virtio/virtio_mem.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>> index 10ec60d..8185916 100644
>> --- a/drivers/virtio/virtio_mem.c
>> +++ b/drivers/virtio/virtio_mem.c
>> @@ -2472,8 +2472,9 @@ static int virtio_mem_init(struct virtio_mem *vm)
>>  	vm->offline_threshold = max_t(uint64_t, 2 * memory_block_size_bytes(),
>>  				      VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD);
>>  	/* In BBM, we also want at least two big blocks. */
>> -	vm->offline_threshold = max_t(uint64_t, 2 * vm->bbm.bb_size,
>> -				      vm->offline_threshold);
>> +	if (!vm->in_sbm)
>> +		vm->offline_threshold = max_t(uint64_t, 2 * vm->bbm.bb_size,
>> +					      vm->offline_threshold);
>>    	dev_info(&vm->vdev->dev, "start address: 0x%llx", vm->addr);
>>  	dev_info(&vm->vdev->dev, "region size: 0x%llx", vm->region_size);
> 
> Good that you also spotted it, I already have a fix pending for that :)
> 
> https://lkml.kernel.org/r/20210602185720.31821-2-david@redhat.com

Oops!  Please ignore this RFC.

Best,
Hui

> 
> -- 
> Thanks,
> 
> David / dhildenb