linux-kernel - Re: [PATCH v2 07/27] drm/i915/gvt: Don't rely on KVM's gfn_to

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Date:   Fri, 17 Mar 2023 13:37:21 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>,
        <intel-gvt-dev@...ts.freedesktop.org>,
        <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v2 07/27] drm/i915/gvt: Don't rely on KVM's gfn_to_pfn()
 to query possible 2M GTT

On Fri, Mar 10, 2023 at 04:22:38PM -0800, Sean Christopherson wrote:
>  /*
> - * Check if can do 2M page
> + * Try to map a 2M gtt entry.
>   * @vgpu: target vgpu
>   * @entry: target pfn's gtt entry
>   *
> - * Return 1 if 2MB huge gtt shadowing is possible, 0 if miscondition,
> - * negative if found err.
> + * Return 1 if 2MB huge gtt shadow was creation, 0 if the entry needs to be
> + * split, negative if found err.
>   */
> -static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
> -	struct intel_gvt_gtt_entry *entry)
> +static int try_map_2MB_gtt_entry(struct intel_vgpu *vgpu,
> +	struct intel_gvt_gtt_entry *entry, dma_addr_t *dma_addr)
>  {
>  	const struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
>  	unsigned long gfn = ops->get_pfn(entry);
> -	kvm_pfn_t pfn;
>  	int max_level;
> -	int ret;
>  
>  	if (!HAS_PAGE_SIZES(vgpu->gvt->gt->i915, I915_GTT_PAGE_SIZE_2M))
>  		return 0;
> @@ -1173,16 +1171,7 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
>  	if (max_level < PG_LEVEL_2M)
>  		return 0;
>  
> -	pfn = gfn_to_pfn(vgpu->vfio_device.kvm, gfn);
> -	if (is_error_noslot_pfn(pfn))
> -		return -EINVAL;
> -
> -	if (!pfn_valid(pfn))
> -		return -EINVAL;
> -
> -	ret = PageTransHuge(pfn_to_page(pfn));
> -	kvm_release_pfn_clean(pfn);
> -	return ret;
> +	return intel_gvt_dma_map_guest_page(vgpu, gfn, I915_GTT_PAGE_SIZE_2M, dma_addr);
intel_gvt_dma_map_guest_page() returns 0 on success, which is not in
consistent with the expected return value of this function, i.e.
"
Return 1 if 2MB huge gtt shadow was creation, 0 if the entry needs to be
split, negative if found err.
"