linux-kernel - Re: [PATCH v2 02/18] x86/sgx: Store struct sgx

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Date:   Fri, 02 Dec 2022 13:40:26 -0800
From:   Kristen Carlson Accardi <kristen@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>, jarkko@...nel.org,
        dave.hansen@...ux.intel.com, tj@...nel.org,
        linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
        cgroups@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Cc:     zhiquan1.li@...el.com, Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v2 02/18] x86/sgx: Store struct sgx_encl when allocating
 new VA pages

On Fri, 2022-12-02 at 13:35 -0800, Dave Hansen wrote:
> On 12/2/22 10:36, Kristen Carlson Accardi wrote:
> > When allocating new Version Array (VA) pages, pass the struct
> > sgx_encl
> > of the enclave that is allocating the page. sgx_alloc_epc_page()
> > will
> > store this value in the encl_owner field of the struct
> > sgx_epc_page. In
> > a later patch, VA pages will be placed in an unreclaimable queue,
> > and then when the cgroup max limit is reached and there are no more
> > reclaimable pages and the enclave must be oom killed, all the
> > VA pages associated with that enclave can be uncharged and freed.
> 
> What does this have to do with the 'encl' that is being passed,
> though?
> 
> In other words, why is this new sgx_epc_page-to-encl mapping needed
> for
> VA pages now, but it wasn't before?

When we OOM kill an enclave, we want to get rid of all the associated
VA pages too. Prior to this patch, there wasn't a way to easily get the
VA pages associated with an enclave.