linux-kernel - Re: [PATCH] x86/cpufeatures: SGX: Adjust the error message when BIOS does not support SGX

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Message-ID: <9b1b4ef92b8d70bf8072fbbd07f70f82335b9040.camel@intel.com>
Date: Tue, 30 Jul 2024 22:48:29 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>
CC: "baimingcong@...ontech.com" <baimingcong@...ontech.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>, "bp@...en8.de"
	<bp@...en8.de>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"jarkko@...nel.org" <jarkko@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
	"wangyuli@...ontech.com" <wangyuli@...ontech.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "x86@...nel.org" <x86@...nel.org>, "mingo@...hat.com"
	<mingo@...hat.com>, "xiangzelong@...ontech.com" <xiangzelong@...ontech.com>,
	"wubo@...ontech.com" <wubo@...ontech.com>, "guanwentao@...ontech.com"
	<guanwentao@...ontech.com>, "haitao.huang@...ux.intel.com"
	<haitao.huang@...ux.intel.com>
Subject: Re: [PATCH] x86/cpufeatures: SGX: Adjust the error message when BIOS
 does not support SGX

On Tue, 2024-07-30 at 10:56 -0700, Sean Christopherson wrote:
> On Tue, Jul 30, 2024, Kai Huang wrote:
> > On Tue, 2024-07-30 at 10:49 +0800, WangYuli wrote:
> > > When SGX is not supported by the BIOS, we still output the error
> > > 'SGX disabled by BIOS', which can be confusing since there might not be
> > > an SGX-related option in the BIOS settings.
> > 
> > +linux-sgx list, Jarkko, Haitao.
> > 
> > This message is only printed when SGX is reported in CPUID but is not
> > enabled in the FEAT_CTL MSR.  I can only recall this can happen when the
> > BIOS actually provides an option for the user to turn on/off SGX, in
> > which case the current message is correct.
> 
> FWIW, this could easily happen with a virtual machine, e.g. running an old QEMU
> with `-cpu host`.
> 

Hmm.. it appears so, if the old Qemu doesn't have SGX support.  Thanks.

Perhaps "SGX disabled or unsupported by BIOS." or "SGX not enabled by
BIOS" is slightly better than the current "SGX disabled by BIOS", but I
am not sure whether it is worth patching.