Re: [RFC PATCH v3 03/10] x86/sgx: Save enclave pointer for VA page

Jarkko Sakkinen
2022-04-06T10:03:27Z

On Wed, 2022-04-06 at 03:31 +0000, Zhang, Cathy wrote:
>
>
> > -----Original Message-----
> > From: Jarkko Sakkinen <jarkko@kernel.org>
> > Sent: Sunday, April 3, 2022 6:08 PM
> > To: Zhang, Cathy <cathy.zhang@intel.com>
> > Cc: linux-sgx@vger.kernel.org; x86@kernel.org; Chatre, Reinette
> > <reinette.chatre@intel.com>; Hansen, Dave <dave.hansen@intel.com>; Raj,
> > Ashok <ashok.raj@intel.com>
> > Subject: Re: [RFC PATCH v3 03/10] x86/sgx: Save enclave pointer for VA page
> >
> > On Fri, Apr 01, 2022 at 10:24:02PM +0800, Cathy Zhang wrote:
> > > Tearing down all enclaves is required by SGX SVN update, which
> > > involves running the ENCLS[EREMOVE] instruction on every EPC page.
> > > This (tearing down all enclaves) should be coordinated with any
> > > enclaves that may be in the process of existing and thus already be
> > > running ENCLS[EREMOVE] as part of enclave release.
> > >
> > > In support of this coordination, it is required to know which enclave
> > > owns each in-use EPC page. It is already possible to locate the owning
> > > enclave of SECS and regular pages but not for VA pages.
> > >
> > > Save the enclave pointer for each VA page to support locating its
> > > owning enclave.
> > >
> > > Note: to track 2T EPC memory, this scheme of tracking will use
> > > additional 8M memory.
> > >
> > > Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
> > > ---
> > >  arch/x86/kernel/cpu/sgx/encl.h  | 1 +
> > > arch/x86/kernel/cpu/sgx/ioctl.c | 1 +
> > >  2 files changed, 2 insertions(+)
> > >
> > > diff --git a/arch/x86/kernel/cpu/sgx/encl.h
> > > b/arch/x86/kernel/cpu/sgx/encl.h index 0c8571fc30cf..59fbd4ed5c64
> > > 100644
> > > --- a/arch/x86/kernel/cpu/sgx/encl.h
> > > +++ b/arch/x86/kernel/cpu/sgx/encl.h
> > > @@ -76,6 +76,7 @@ struct sgx_va_page {
> > >         struct sgx_epc_page *epc_page;
> > >         DECLARE_BITMAP(slots, SGX_VA_SLOT_COUNT);
> > >         struct list_head list;
> > > +       struct sgx_encl *encl;
> > >  };
> > >
> > >  struct sgx_backing {
> > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c
> > > b/arch/x86/kernel/cpu/sgx/ioctl.c index f0ce96bd462a..da82abbb81b4
> > > 100644
> > > --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> > > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> > > @@ -30,6 +30,7 @@ static struct sgx_va_page *sgx_encl_grow(struct
> > sgx_encl *encl)
> > >                 if (!va_page)
> > >                         return ERR_PTR(-ENOMEM);
> > >
> > > +               va_page->encl = encl;
> > >                 va_page->epc_page = sgx_alloc_va_page(va_page);
> > >                 if (IS_ERR(va_page->epc_page)) {
> > >                         err = ERR_CAST(va_page->epc_page);
> > > --
> > > 2.17.1
> > >
> >
> > Squash this with the previous patch. Then the code will provide
> > answer to one of the questions that I mentioned in 2/10 review.
> >
> > BR, Jarkko
>
> Squashed. How about re-write the commit log as follows:
>
> x86/sgx: Save enclave pointer for VA page
>
> Tearing down all enclaves is required by SGX SVN update, which
> involves running the ENCLS[EREMOVE] instruction on every EPC
> page. This (tearing down all enclaves) should be coordinated
> with any enclaves that may be in the process of existing and thus
> already be running ENCLS[EREMOVE] as part of enclave release.
>
> In support of this coordination, it is required to know which enclave
> owns each in-use EPC page. It is already possible to locate the
> owning enclave of SECS and regular pages but not for VA pages.
>
> Make the following changes for VA page's location:
> 1) Make epc->owner type-agnostic by change its type to 'void *'. So,
>    besides "struct sgx_encl_page", it can have other types, like
>    "struct sgx_va_page".
> 2) Save the enclave pointer for each VA page to support locating its
>    owning enclave.
>
> Note: to track 2T EPC memory, this scheme of tracking will use
> additional 8M memory.

Sounds good to me.

BR, Jarkko