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Message-ID: <abfc00a2ab1d97f8081c696f78e2d0ced23902b4.camel@linux.intel.com>
Subject: Re: [PATCH v2 02/18] x86/sgx: Store struct sgx_encl when allocating
 new VA pages
From:   Kristen Carlson Accardi <kristen@linux.intel.com>
To:     Dave Hansen <dave.hansen@intel.com>, jarkko@kernel.org,
        dave.hansen@linux.intel.com, tj@kernel.org,
        linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org,
        cgroups@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Cc:     zhiquan1.li@intel.com, Sean Christopherson <seanjc@google.com>
Date:   Fri, 02 Dec 2022 13:40:26 -0800
In-Reply-To: <3a789b1c-4c70-158b-d764-daec141a5816@intel.com>
References: <20221202183655.3767674-1-kristen@linux.intel.com>
         <20221202183655.3767674-3-kristen@linux.intel.com>
         <3a789b1c-4c70-158b-d764-daec141a5816@intel.com>
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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.
>=20
> What does this have to do with the 'encl' that is being passed,
> though?
>=20
> 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.