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Re: [Qemu-block] Virtio-BLK/SCSI write requests and data payload checksu

From: Peter Lieven
Subject: Re: [Qemu-block] Virtio-BLK/SCSI write requests and data payload checksums
Date: Tue, 18 Dec 2018 15:45:00 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

Am 18.12.18 um 14:15 schrieb Vadim Rozenfeld:
> Peter, I must be missing something here, but what exactly the problem
> is?

The issue is that I see concurrent read requests coming in from Windows Guest 
with vioscsi as driver that

have the same buffer address from guest memory space. I noticed this because I 
have Data Digests enabled

and the calculated Digest has a wrong CRC32C. This happens because the CRC is 
calculated while or after data

from a second requests reads into the same buffer. I see this only with Windows 
and the request size seems

to be always 4K. This is either a bug in Windows, vioscsi or a mad application 
issuing concurrent reads using

the same buffer. From what I have seen in the dumps of the data that has been 
read it seems not to be one

common application.



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