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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Wed, 25 Apr 2018 07:23:53 -0700
Message-ID: <CAPcyv4gpZzKfE7jY1peYOVd6sVhNz7jce1s_xNH_2Lt8AjRK-Q@mail.gmail.com>
Subject: Re: [RFC v2 2/2] pmem: device flush over VIRTIO
To:     Pankaj Gupta <pagupta@redhat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        KVM list <kvm@vger.kernel.org>,
        Qemu Developers <qemu-devel@nongnu.org>,
        linux-nvdimm <linux-nvdimm@ml01.01.org>,
        Linux MM <linux-mm@kvack.org>, Jan Kara <jack@suse.cz>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Rik van Riel <riel@surriel.com>,
        Haozhong Zhang <haozhong.zhang@intel.com>,
        Nitesh Narayan Lal <nilal@redhat.com>,
        Kevin Wolf <kwolf@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "Zwisler, Ross" <ross.zwisler@intel.com>,
        David Hildenbrand <david@redhat.com>,
        Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
        Christoph Hellwig <hch@infradead.org>,
        Marcel Apfelbaum <marcel@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        niteshnarayanlal@hotmail.com, Igor Mammedov <imammedo@redhat.com>,
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On Wed, Apr 25, 2018 at 4:24 AM, Pankaj Gupta <pagupta@redhat.com> wrote:
> This patch adds functionality to perform
> flush from guest to hosy over VIRTIO
> when 'ND_REGION_VIRTIO'flag is set on
> nd_negion. Flag is set by 'virtio-pmem'
> driver.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/nvdimm/region_devs.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index a612be6..6c6454e 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -20,6 +20,7 @@
>  #include <linux/nd.h>
>  #include "nd-core.h"
>  #include "nd.h"
> +#include <linux/virtio_pmem.h>
>
>  /*
>   * For readq() and writeq() on 32-bit builds, the hi-lo, lo-hi order is
> @@ -1074,6 +1075,12 @@ void nvdimm_flush(struct nd_region *nd_region)
>         struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
>         int i, idx;
>
> +       /* call PV device flush */
> +       if (test_bit(ND_REGION_VIRTIO, &nd_region->flags)) {
> +               virtio_pmem_flush(&nd_region->dev);
> +               return;
> +       }
> +

I'd rather introduce a ->flush() operation hanging off of 'struct
nd_region' so that this multiplexing can be a static setting.