linux-kernel - Re: [PATCH v12 1/5] x86/sgx: Introduce functions to count the sgx_(vepc

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Message-ID: <72d687ff28096fcf3c90b3b4783de902fbaa721a.camel@intel.com>
Date: Mon, 11 Aug 2025 10:23:27 +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 v12 1/5] x86/sgx: Introduce functions to count the
 sgx_(vepc_)open()

On Mon, 2025-08-11 at 12:06 +0300, Elena Reshetova wrote:
> Currently, when SGX is compromised and the microcode update fix is applied,
> the machine needs to be rebooted to invalidate old SGX crypto-assets and
> make SGX be in an updated safe state. It's not friendly for the cloud.
> 
> To avoid having to reboot, a new ENCLS[EUPDATESVN] is introduced to update
> SGX environment at runtime. This process needs to be done when there's no
> SGX users to make sure no compromised enclaves can survive from the update
> and allow the system to regenerate crypto-assets.
> 
> For now there's no counter to track the active SGX users of host enclave
> and virtual EPC. Introduce such counter mechanism so that the EUPDATESVN
> can be done only when there's no SGX users.
> 
> Define placeholder functions sgx_inc/dec_usage_count() that are used to
> increment and decrement such a counter. Also, wire the call sites for
> these functions. Encapsulate the current sgx_(vepc_)open() to
> __sgx_(vepc_)open() to make the new sgx_(vepc_)open() easy to read.
> 
> The definition of the counter itself and the actual implementation of
> sgx_inc/dec_usage_count() functions come next.
> 
> Note: The EUPDATESVN, which may fail, will be done in
> sgx_inc_usage_count(). Make it return 'int' to make subsequent patches
> which implement EUPDATESVN easier to review. For now it always returns
> success.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>

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