linux-kernel - RE: [PATCH v5 1/5] x86/sgx: Introduce a counter to count the sgx_(vepc

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Message-ID: <DM8PR11MB5750A29C0878480F6F19E39BE79CA@DM8PR11MB5750.namprd11.prod.outlook.com>
Date: Mon, 19 May 2025 11:47:32 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: "Huang, Kai" <kai.huang@...el.com>, "Hansen, Dave" <dave.hansen@...el.com>
CC: "Raynor, Scott" <scott.raynor@...el.com>, "linux-sgx@...r.kernel.org"
	<linux-sgx@...r.kernel.org>, "Scarlata, Vincent R"
	<vincent.r.scarlata@...el.com>, "x86@...nel.org" <x86@...nel.org>,
	"jarkko@...nel.org" <jarkko@...nel.org>, "Annapurve, Vishal"
	<vannapurve@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Mallick, Asit K" <asit.k.mallick@...el.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>, "Cai, Chong" <chongc@...gle.com>,
	"bondarn@...gle.com" <bondarn@...gle.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "dionnaglaze@...gle.com" <dionnaglaze@...gle.com>
Subject: RE: [PATCH v5 1/5] x86/sgx: Introduce a counter to count the
 sgx_(vepc_)open()

> On Mon, 2025-05-19 at 10:24 +0300, Elena Reshetova wrote:
> > Currently SGX does not have a global counter to count the
> > active users from userspace or hypervisor. Implement such a counter,
> > sgx_usage_count. It will be used by the driver when attempting
> > to call EUPDATESVN SGX instruction.
> >
> > Suggested-by: Sean Christopherson <seanjc@...gle.com>
> > Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> > ---
> >  arch/x86/kernel/cpu/sgx/driver.c |  1 +
> >  arch/x86/kernel/cpu/sgx/encl.c   |  1 +
> >  arch/x86/kernel/cpu/sgx/main.c   | 14 ++++++++++++++
> >  arch/x86/kernel/cpu/sgx/sgx.h    |  3 +++
> >  arch/x86/kernel/cpu/sgx/virt.c   |  2 ++
> >  5 files changed, 21 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/driver.c
> b/arch/x86/kernel/cpu/sgx/driver.c
> > index 7f8d1e11dbee..b5ffe104af4c 100644
> > --- a/arch/x86/kernel/cpu/sgx/driver.c
> > +++ b/arch/x86/kernel/cpu/sgx/driver.c
> > @@ -19,6 +19,7 @@ static int sgx_open(struct inode *inode, struct file *file)
> >  	struct sgx_encl *encl;
> >  	int ret;
> >
> > +	sgx_inc_usage_count();
> 
> This should be done at the end of sgx_open() where the open cannot fail,
> since
> sgx_release() is not called if sgx_open() failed AFAICT.


Could you please elaborate a bit more on this? 
In case sgx_inc_usage_count fails, we dont allocate resources yet, so what is 
wrong? 

Best Regards,
Elena.