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 20:47:46 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jarkko Sakkinen" <jarkko@...nel.org>, "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 8:44 PM EEST, Jarkko Sakkinen wrote:
> 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.

Good that you asked that had rethink for a while.

What I would suggest that you just put out 2nd verson out and then we
see where it is going.

For sgx_ioc_encl_add_pages() it is important to maintain exact semantics
as we need to maintain backwards compatibility.

BR, Jarkko