linux-kernel - Re: [RFC PATCH 1/1] x86/sgx: Explicitly give up the CPU in EDMM's ioctl() to avoid softlockup

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Date: Wed, 24 Apr 2024 20:44:07 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Bojun Zhu" <zhubojun.zbj@...group.com>
Cc: "Huang, Kai" <kai.huang@...el.com>, "linux-sgx@...r.kernel.org"
 <linux-sgx@...r.kernel.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "dave.hansen@...ux.intel.com"
 <dave.hansen@...ux.intel.com>, 刘双(轩屹)
 <ls123674@...group.com>, "Chatre, Reinette" <reinette.chatre@...el.com>
Subject: Re: [RFC PATCH 1/1] x86/sgx: Explicitly give up the CPU in EDMM's
 ioctl() to avoid softlockup

On Wed Apr 24, 2024 at 2:50 PM EEST, Bojun Zhu wrote:
> I still have some questions:
>
> It seems that the variable "ret" is set to 0 if there is **some** EPC pages have been 
> added when interrupted by signal(Supposed that sgx_encl_add_page() 
> always returns successfully).

Ah, ok.

Returning zero is right thing to do because it also returns count of
pages successfully added. I.e. the function does not guarantee that
all pages are processsed but it does guarantee that the system is in
predictable state.

It could be that e.g. sgx_alloc_epc_page() calls fails.

So, it is a bit like how read system call works.

BR, Jarkko