linux-kernel - Re: [PATCH 1/1] iommu/amd: Preserve default DTE fields when updating Host Page Table Root

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Message-ID: <Z8Gbe6InZ862dn6E@8bytes.org>
Date: Fri, 28 Feb 2025 12:18:19 +0100
From: Joerg Roedel <joro@...tes.org>
To: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
	suravee.suthikulpanit@....com, vasant.hegde@....com,
	will@...nel.org, jgg@...dia.com, joao.m.martins@...cle.com,
	boris.ostrovsky@...cle.com
Subject: Re: [PATCH 1/1] iommu/amd: Preserve default DTE fields when updating
 Host Page Table Root

On Mon, Jan 06, 2025 at 07:14:13PM +0000, Alejandro Jimenez wrote:
> When updating the page table root field on the DTE, avoid overwriting any
> bits that are already set. The earlier call to make_clear_dte() writes
> default values that all DTEs must have set (currently DTE[V]), and those
> must be preserved.
> 
> Currently this doesn't cause problems since the page table root update is
> the first field that is set after make_clear_dte() is called, and
> DTE_FLAG_V is set again later along with the permission bits (IR/IW).
> Remove this redundant assignment too.
> 
> Fixes: fd5dff9de4be ("iommu/amd: Modify set_dte_entry() to use 256-bit DTE helpers")
> Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
> ---
>  drivers/iommu/amd/iommu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied, thanks.