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

Zhang, Cathy
2022-04-06T12:16:24Z

> -----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.