linux-kernel - RE: [RFCv2 PATCH 2/7] iommu/amd: Refactor set_dte

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Date: Mon, 22 Jan 2024 08:39:57 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, "joro@...tes.org"
	<joro@...tes.org>, "jgg@...dia.com" <jgg@...dia.com>
CC: "Liu, Yi L" <yi.l.liu@...el.com>, "nicolinc@...dia.com"
	<nicolinc@...dia.com>, "eric.auger@...hat.com" <eric.auger@...hat.com>,
	"vasant.hegde@....com" <vasant.hegde@....com>, "jon.grimm@....com"
	<jon.grimm@....com>, "santosh.shukla@....com" <santosh.shukla@....com>,
	"Dhaval.Giani@....com" <Dhaval.Giani@....com>, "pandoh@...gle.com"
	<pandoh@...gle.com>, "loganodell@...gle.com" <loganodell@...gle.com>
Subject: RE: [RFCv2 PATCH 2/7] iommu/amd: Refactor set_dte_entry

> From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> Sent: Friday, January 12, 2024 8:07 AM
> 
> +
> +	/* Use system default */
> +	tmp = amd_iommu_gpt_level;
> +
> +	/* Mask out old values for GuestPagingMode */
> +	target->data[2] &= ~(0x3ULL << DTE_GPT_LEVEL_SHIFT);
> +	target->data[2] |= (tmp << DTE_GPT_LEVEL_SHIFT);

Just directly use amd_iommu_gpt_level here.

btw this sounds like a functional change as the original code only does
this for 5level:

		if (amd_iommu_gpt_level == PAGE_MODE_5_LEVEL) {
			dev_table[devid].data[2] |=
				((u64)GUEST_PGTABLE_5_LEVEL <<
DTE_GPT_LEVEL_SHIFT);
		}

If it's the desired change then better make it a separate fix.