linux-kernel - Re: DAX can not work on virtual nvdimm device

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Date:   Wed, 31 Aug 2016 16:44:47 +0800
From:   Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Yumei Huang <yuhuang@...hat.com>, KVM <kvm@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>
Subject: Re: DAX can not work on virtual nvdimm device



On 08/31/2016 01:09 AM, Dan Williams wrote:

>
> Can you post your exact reproduction steps?  This test is not failing for me.
>

Sure.

1. make the guest kernel based on your tree, the top commit is
    10d7902fa0e82b (dax: unmap/truncate on device shutdown) and
    the config file can be found in this thread.

2. add guest kernel command line: memmap=6G!10G

3: start the guest:
    x86_64-softmmu/qemu-system-x86_64 -machine pc,nvdimm --enable-kvm \
    -smp 16 -m 32G,maxmem=100G,slots=100 /other/VMs/centos6.img -monitor stdio

4: in guest:
    mkfs.ext4 /dev/pmem0
    mount -o dax /dev/pmem0  /mnt/pmem/
    echo > /mnt/pmem/xxx
    ./mmap /mnt/pmem/xxx
    ./read /mnt/pmem/xxx

   The source code of mmap and read has been attached in this mail.

   Hopefully, you can detect the error triggered by read test.

Thanks!

View attachment "read.c" of type "text/x-csrc" (763 bytes)

View attachment "mmap.c" of type "text/x-csrc" (2064 bytes)