linux-kernel - RE: [PATCH v2 16/26] drm/xe/pf: Add helpers for VF GGTT migration data handling

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Message-ID: <BN9PR11MB5276E25C0636FAFDF1D4FDE48CFDA@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Tue, 28 Oct 2025 03:22:46 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: "Winiarski, Michal" <michal.winiarski@...el.com>, Alex Williamson
	<alex.williamson@...hat.com>, "De Marchi, Lucas" <lucas.demarchi@...el.com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	"Vivi, Rodrigo" <rodrigo.vivi@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
	Yishai Hadas <yishaih@...dia.com>, "intel-xe@...ts.freedesktop.org"
	<intel-xe@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Brost, Matthew" <matthew.brost@...el.com>, "Wajdeczko, Michal"
	<Michal.Wajdeczko@...el.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "Jani
 Nikula" <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Laguna,
 Lukasz" <lukasz.laguna@...el.com>
Subject: RE: [PATCH v2 16/26] drm/xe/pf: Add helpers for VF GGTT migration
 data handling

> From: Winiarski, Michal <michal.winiarski@...el.com>
> Sent: Wednesday, October 22, 2025 6:41 AM
> 
> +int xe_ggtt_node_load(struct xe_ggtt_node *node, const void *src, size_t
> size, u16 vfid)
> +{
> +	u64 vfid_pte = xe_encode_vfid_pte(vfid);
> +	const u64 *buf = src;
> +	struct xe_ggtt *ggtt;
> +	u64 start, end;
> +
> +	if (!node)
> +		return -ENOENT;
> +
> +	guard(mutex)(&node->ggtt->lock);
> +
> +	ggtt = node->ggtt;
> +	start = node->base.start;
> +	end = start + size - 1;
> +
> +	if (xe_ggtt_pte_size(ggtt, node->base.size) != size)
> +		return -EINVAL;
> +
> +	while (start < end) {
> +		ggtt->pt_ops->ggtt_set_pte(ggtt, start, (*buf &
> ~GGTT_PTE_VFID) | vfid_pte);
> +		start += XE_PAGE_SIZE;
> +		buf++;
> +	}

static u64 xe_encode_vfid_pte(u16 vfid)
{
        return FIELD_PREP(GGTT_PTE_VFID, vfid) | XE_PAGE_PRESENT;
}

so above loop blindly set every GGTT entry to valid. Isn't the right
thing to carry the present bit from the src buffer?