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Date:   Tue, 28 Apr 2020 15:53:55 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@kernel.org>
To:     Srivatsa Vaddagiri <vatsa@codeaurora.org>
cc:     konrad.wilk@oracle.com, mst@redhat.com, jasowang@redhat.com,
        jan.kiszka@siemens.com, will@kernel.org,
        stefano.stabellini@xilinx.com, iommu@lists.linux-foundation.org,
        virtualization@lists.linux-foundation.org,
        virtio-dev@lists.oasis-open.org, tsoni@codeaurora.org,
        pratikp@codeaurora.org, christoffer.dall@arm.com,
        alex.bennee@linaro.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops
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Message-ID: <alpine.DEB.2.21.2004281542010.29217@sstabellini-ThinkPad-T480s>
References: <1588073958-1793-1-git-send-email-vatsa@codeaurora.org> <1588073958-1793-6-git-send-email-vatsa@codeaurora.org>
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On Tue, 28 Apr 2020, Srivatsa Vaddagiri wrote:
> For better security, its desirable that a guest VM's memory is
> not accessible to any entity that executes outside the context of
> guest VM. In case of virtio, backend drivers execute outside the
> context of guest VM and in general will need access to complete
> guest VM memory.  One option to restrict the access provided to
> backend driver is to make use of a bounce buffer. The bounce
> buffer is accessible to both backend and frontend drivers. All IO
> buffers that are in private space of guest VM are bounced to be
> accessible to backend.

[...]

> +static int __init virtio_bounce_setup(struct reserved_mem *rmem)
> +{
> +	unsigned long node = rmem->fdt_node;
> +
> +	if (!of_get_flat_dt_prop(node, "no-map", NULL))
> +		return -EINVAL;
> +
> +	return virtio_register_bounce_buffer(rmem->base, rmem->size);
> +}
> +
> +RESERVEDMEM_OF_DECLARE(virtio, "virtio_bounce_pool", virtio_bounce_setup);

Is this special reserved-memory region documented somewhere?