linux-kernel - Re: [PATCH v2 03/18] x86/sgx: Add 'struct sgx_epc_lru

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Message-ID: <08a420401b2fb539f37cbf21a0ded6bf8c68c72b.camel@linux.intel.com>
Date:   Thu, 08 Dec 2022 10:03:04 -0800
From:   Kristen Carlson Accardi <kristen@...ux.intel.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     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>,
        zhiquan1.li@...el.com, Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v2 03/18] x86/sgx: Add 'struct sgx_epc_lru_lists' to
 encapsulate lru list(s)

On Thu, 2022-12-08 at 15:31 +0000, Jarkko Sakkinen wrote:
> On Fri, Dec 02, 2022 at 10:36:39AM -0800, Kristen Carlson Accardi
> wrote:
> > Introduce a data structure to wrap the existing reclaimable list
> > and its spinlock in a struct to minimize the code changes needed
> > to handle multiple LRUs as well as reclaimable and non-reclaimable
> > lists, both of which will be introduced and used by SGX EPC
> > cgroups.
> > 
> > Signed-off-by: Sean Christopherson
> > <sean.j.christopherson@...el.com>
> > Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
> > Cc: Sean Christopherson <seanjc@...gle.com>
> > ---
> >  arch/x86/kernel/cpu/sgx/sgx.h | 65
> > +++++++++++++++++++++++++++++++++++
> >  1 file changed, 65 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/cpu/sgx/sgx.h
> > b/arch/x86/kernel/cpu/sgx/sgx.h
> > index 39cb15a8abcb..5e6d88438fae 100644
> > --- a/arch/x86/kernel/cpu/sgx/sgx.h
> > +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> > @@ -90,6 +90,71 @@ static inline void *sgx_get_epc_virt_addr(struct
> > sgx_epc_page *page)
> >         return section->virt_addr + index * PAGE_SIZE;
> >  }
> >  
> > +/*
> > + * This data structure wraps a list of reclaimable EPC pages, and
> > a list of
> > + * non-reclaimable EPC pages and is used to implement a LRU policy
> > during
> > + * reclamation.
> > + */
> > +struct sgx_epc_lru_lists {
> > +       spinlock_t lock;
> > +       struct list_head reclaimable;
> > +       struct list_head unreclaimable;
> > +};
>  
> Why this is named like this, and not sgx_epc_global_rcu? Are there
> any other use cases?
> 
> BR, Jarkko

Yes, there are other use cases that are introduced in the other
patches. This structure is used to in the cgroup struct to hold cgroup
specific LRUs.