linux-kernel - RE: [PATCH v6 4/5] x86/sgx: Implement ENCLS[EUPDATESVN]

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Message-ID: <DM8PR11MB575031F880D9B79D2A1D797EE765A@DM8PR11MB5750.namprd11.prod.outlook.com>
Date: Mon, 26 May 2025 11:09:31 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
CC: "Hansen, Dave" <dave.hansen@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>, "mingo@...nel.org"
	<mingo@...nel.org>, "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, "Mallick, Asit K"
	<asit.k.mallick@...el.com>, "Scarlata, Vincent R"
	<vincent.r.scarlata@...el.com>, "Cai, Chong" <chongc@...gle.com>, "Aktas,
 Erdem" <erdemaktas@...gle.com>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"dionnaglaze@...gle.com" <dionnaglaze@...gle.com>, "bondarn@...gle.com"
	<bondarn@...gle.com>, "Raynor, Scott" <scott.raynor@...el.com>
Subject: RE: [PATCH v6 4/5] x86/sgx: Implement ENCLS[EUPDATESVN]

> > +	/*
> > +	 * SVN was already up-to-date. This is the most
> > +	 * common case.
> > +	 */
> > +	if (ret == SGX_NO_UPDATE)
> > +		return 0;
> > +
> > +	/*
> > +	 * SVN update failed due to lack of entropy in DRNG.
> > +	 * Indicate to userspace that it should retry.
> > +	 */
> > +	if (ret == SGX_INSUFFICIENT_ENTROPY)
> > +		return -EAGAIN;
> > +
> > +	if (!ret) {
> > +		/*
> > +		 * SVN successfully updated.
> > +		 * Let users know when the update was successful.
> > +		 */
> > +		pr_info("SVN updated successfully\n");
> > +		return 0;
> > +	}
> > +
> > +	/*
> > +	 * EUPDATESVN was called when EPC is empty, all other error
> > +	 * codes are unexpected.
> > +	 */
> > +	ENCLS_WARN(ret, "EUPDATESVN");
> > +	return -EIO;
> > +}
> 
> Even if unlikely() was not used I still don't agree with the order i.e.,
> dealing with the success case in the middle. So I stand with my earlier
> suggestion, except unlikely() (since that was a problem for David, not
> going to fight over it).

I can change the order in the next patch if this is what everyone agrees on.
So, your preference would be to have smth like this:

+	/*
+	 * SVN successfully updated.
+	* Let users know when the update was successful.
+	*/
+	if (!ret) 
+		pr_info("SVN updated successfully\n");
+	
+	if (!ret) || (ret == SGX_NO_UPDATE)
+		return 0;
+
+	/*
+	 * SVN update failed due to lack of entropy in DRNG.
+	 * Indicate to userspace that it should retry.
+	 */
+	if (ret == SGX_INSUFFICIENT_ENTROPY)
+		return -EAGAIN;
+
+	/*
+	 * EUPDATESVN was called when EPC is empty, all other error
+	 * codes are unexpected.
+	 */
+	ENCLS_WARN(ret, "EUPDATESVN");
+	return -EIO;