linux-kernel - Re: [PATCH 1/6] x86/sgx: Do not consider unsanitized pages an error

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Message-ID: <Yw7EX5GCrEaLzpHV@kernel.org>
Date:   Wed, 31 Aug 2022 05:15:59 +0300
From:   "jarkko@...nel.org" <jarkko@...nel.org>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pmenzel@...gen.mpg.de" <pmenzel@...gen.mpg.de>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "Dhanraj, Vijay" <vijay.dhanraj@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "hpa@...or.com" <hpa@...or.com>,
        "haitao.huang@...ux.intel.com" <haitao.huang@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] x86/sgx: Do not consider unsanitized pages an error

On Wed, Aug 31, 2022 at 01:27:58AM +0000, Huang, Kai wrote:
> On Tue, 2022-08-30 at 15:54 -0700, Reinette Chatre wrote:
> > Hi Jarkko,
> > 
> > On 8/29/2022 8:12 PM, Jarkko Sakkinen wrote:
> > > In sgx_init(), if misc_register() for the provision device fails, and
> > > neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
> > > prematurely stopped.
> > 
> > I do not think misc_register() is required to fail for the scenario to
> > be triggered (rather use "or" than "and"?). Perhaps just
> > "In sgx_init(), if a failure is encountered after ksgxd is started
> > (via sgx_page_reclaimer_init()) ...".
> 
> IMHO "a failure" might be too vague.  For instance, failure to sgx_drv_init()
> won't immediately result in ksgxd to stop prematurally.  As long as KVM SGX can
> be initialized successfully, sgx_init() still returns 0.
> 
> Btw I was thinking whether we should move sgx_page_reclaimer_init() to the end
> of sgx_init(), after we make sure at least one of the driver and the KVM SGX is
> initialized successfully.  Then the code change in this patch won't be necessary
> if I understand correctly.  AFAICT there's no good reason to start the ksgxd at
> early stage before we are sure either the driver or KVM SGX will work.

I would focus fixing the existing flow rather than reinventing the flow.

It can be made to work, and therefore it is IMHO correct action to take.

> Btw currently EPC pages assigned to KVM guest cannot be reclaimed, so
> theoretically ksgxd can be moved to sgx_drv_init(), but who knows someday we
> will decide to make KVM guest EPC pages to be able to be reclaimed. :)

I'm open to changes but it is in my opinion out of context for this.

> 
> 
> 
> -- 
> Thanks,
> -Kai
> 
> 

BR, Jarkko