linux-kernel - Re: [PATCH v14 4/5] x86/sgx: Implement ENCLS[EUPDATESVN]

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Message-ID: <a74ede5f4466572e33c92fceb69136b82c042d7e.camel@intel.com>
Date: Thu, 14 Aug 2025 09:35:39 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Reshetova, Elena" <elena.reshetova@...el.com>, "Hansen, Dave"
	<dave.hansen@...el.com>
CC: "seanjc@...gle.com" <seanjc@...gle.com>, "mingo@...nel.org"
	<mingo@...nel.org>, "Scarlata, Vincent R" <vincent.r.scarlata@...el.com>,
	"x86@...nel.org" <x86@...nel.org>, "jarkko@...nel.org" <jarkko@...nel.org>,
	"Annapurve, Vishal" <vannapurve@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Mallick, Asit K" <asit.k.mallick@...el.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "Cai, Chong" <chongc@...gle.com>,
	"Bondarevska, Nataliia" <bondarn@...gle.com>, "linux-sgx@...r.kernel.org"
	<linux-sgx@...r.kernel.org>, "Raynor, Scott" <scott.raynor@...el.com>
Subject: Re: [PATCH v14 4/5] x86/sgx: Implement ENCLS[EUPDATESVN]

On Thu, 2025-08-14 at 10:34 +0300, Reshetova, Elena wrote:
> All running enclaves and cryptographic assets (such as internal SGX
> encryption keys) are assumed to be compromised whenever an SGX-related
> microcode update occurs. To mitigate this assumed compromise the new
> supervisor SGX instruction ENCLS[EUPDATESVN] can generate fresh
> cryptographic assets.
> 
> Before executing EUPDATESVN, all SGX memory must be marked as unused. This
> requirement ensures that no potentially compromised enclave survives the
> update and allows the system to safely regenerate cryptographic assets.
> 
> Add the method to perform ENCLS[EUPDATESVN]. However, until the follow up
> patch that wires calling sgx_update_svn() from sgx_inc_usage_count(), this
> code is not reachable.
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>

Reviewed-by: Kai Huang <kai.huang@...el.com>

> 
> + * Return:
> + * * %0:		- Success or not supported
> + * * %-EAGAIN:		- Can be safely retried, failure is due to lack of
> + * *			entropy in RNG

Nit: if another version is ever needed, I think it would be better to make
the text vertical aligned w/o the leading '-', i.e., 

	* %-EAGAIN:	- Can be ....
			  entropy in RNG.

.. instead of

	* %-EAGAIN:	- Can be ....
			entropy in RNG.