linux-kernel - Re: [PATCH v3 0/1] scsi: ufs: Add crypto_keyslot

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Message-ID: <20251128034736.GA18644@sol>
Date: Thu, 27 Nov 2025 19:47:36 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: "zheng.gong" <zheng.gong@...sung.com>
Cc: linux-scsi@...r.kernel.org, avri.altman@....com, bvanassche@....org,
	quic_cang@...cinc.com, alim.akhtar@...sung.com,
	martin.petersen@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/1] scsi: ufs: Add crypto_keyslot_remap variant op

On Fri, Nov 28, 2025 at 11:37:08AM +0800, zheng.gong wrote:
> Thank you very much for your feedback, Eric. I truly appreciate your review and the time you've taken to point out that a real user is required.
> You're right. Adding a new variant op without a clear use case would not be acceptable. Let me clarify the context behind this patch.

To clarify, there has to be an in-tree user.

> This hook is not theoretical. It is designed to replace an existing out-of-tree variant op (`crypto_keyslot_cfg`) used in Samsung's ExynosAuto UFS driver for multi-VM inline encryption.
> In production, each VM has its own keyslot range per hardware allocation, and the keyslot is remapped at request time:
> 
>     lrbp->crypto_key_slot += vm_id * UFS_KEYSLOTS;
> 
> This was already in use on automotive platforms.
> 
> But the reason this usage isn't visible in mainline is due to ExynosAuto's kernel architecture:
> 
> Starting from kernel 6.1, we adopt the dual-repository model (similar to Android Common Kernel):
> - `kernel.git`: Mainline-based, minimal patches
> - `exynosauto-modules.git`: Hosts platform-specific drivers (as .ko or built-in)
> 
> Our UFS driver, including FMP and IOV support, resides in `exynosauto-modules/drivers/ufs/*`. It couldnot be upstreamed due to:
> - Hardware-specific SMC calls
> - Security-specific key management
> - Non-public register interfaces

The upstream driver is drivers/ufs/host/ufs-exynos.c, so you'll need to
focus on adding this functionality to there, if it's actually needed.
What's happening downstream is irrelevant.

- Eric