linux-kernel - Re: [PATCH 2/3] i915/gvt: save the initial HW state snapshot in i915.

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Date:   Mon, 31 Jan 2022 07:38:03 +0100
From:   Christoph Hellwig <hch@....de>
To:     Zhi Wang <zhi.wang.linux@...il.com>
Cc:     hch@....de, jgg@...dia.com, jani.nikula@...ux.intel.com,
        intel-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Zhi Wang <zhi.a.wang@...el.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Vivi Rodrigo <rodrigo.vivi@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>
Subject: Re: [PATCH 2/3] i915/gvt: save the initial HW state snapshot in
 i915.

On Thu, Jan 27, 2022 at 07:05:07AM -0500, Zhi Wang wrote:
> +static void save_mmio(struct intel_gvt_mmio_table_iter *iter, u32 offset,
> +		      u32 size)
> +{
> +	struct drm_i915_private *dev_priv = iter->i915;
> +	void *mmio = iter->data;
> +	u32 start, end, i;
> +
> +	start = offset;
> +	end = offset + size;
> +
> +	for (i = start; i < end; i += 4) {
> +		*(u32 *)(mmio + i) = intel_uncore_read_notrace(
> +				to_gt(dev_priv)->uncore, _MMIO(offset));
> +	}
> +}

This can be simplified to:

static void intel_gvt_save_mmio(struct intel_gvt_mmio_table_iter *iter,
		u32 offset, u32 size)
{
	struct drm_i915_private *dev_priv = iter->i915;
	u32 *mmio = iter->data, i;

	for (i = offset; i < offset + size; i += 4) {
		mmio[i] = intel_uncore_read_notrace(to_gt(dev_priv)->uncore,
						    _MMIO(offset));
	}
}

> +	struct pci_dev *pdev = to_pci_dev(dev_priv->drm.dev);
> +	struct intel_gvt_device_info info;
> +	struct i915_virtual_gpu *vgpu = &dev_priv->vgpu;
> +	struct intel_gvt_mmio_table_iter iter;
> +	void *mem;
> +	int i, ret;
> +
> +	intel_gvt_init_device_info(dev_priv, &info);

There is no real need for this call.

> +
> +	mem = kzalloc(info.cfg_space_size, GFP_KERNEL);
> +	if (!mem)
> +		return -ENOMEM;

info.cfg_space_size is always PCI_CFG_SPACE_EXP_SIZE, and the code relies
onb that just a few lines below.

> +	mem = vzalloc(info.mmio_size);

And info.mmio_size is a constant that can just use a define.