RE: [PATCH v4 2/9] x86/sgx: Save enclave pointer for VA page

Zhang, Cathy
2022-04-24T02:31:16Z

> -----Original Message-----
> From: Jarkko Sakkinen <jarkko@kernel.org>
> Sent: Friday, April 22, 2022 12:04 AM
> 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>; Peng, Chao P <chao.p.peng@intel.com>;
> Zhong, Yang <yang.zhong@intel.com>
> Subject: Re: [PATCH v4 2/9] x86/sgx: Save enclave pointer for VA page
>
> On Thu, Apr 21, 2022 at 07:03:19PM +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.
> >
> > Make the following changes for VA pages' location:
> > 1) Make epc->owner type-agnostic by changing 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.
> >
> > Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
> >
> > ---
> > Changes since v3:
> > - Squash patch "x86/sgx: Provide VA page non-NULL owner" and
> > "x86/sgx: Save enclave pointer for VA page". Update commit log.
> > (Suggested by Jarkko Sakkinen)
> > ---
> > arch/x86/kernel/cpu/sgx/encl.h | 4 ++--
> > arch/x86/kernel/cpu/sgx/sgx.h | 2 +-
> > arch/x86/kernel/cpu/sgx/encl.c | 5 +++--
> > arch/x86/kernel/cpu/sgx/ioctl.c | 3 ++-
> > 4 files changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/encl.h
> > b/arch/x86/kernel/cpu/sgx/encl.h index 7cdc351bc273..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 {
> > @@ -112,8 +113,7 @@ int sgx_encl_get_backing(struct sgx_encl *encl,
> > unsigned long page_index, void sgx_encl_put_backing(struct
> > sgx_backing *backing, bool do_write); int
> sgx_encl_test_and_clear_young(struct mm_struct *mm,
> > struct sgx_encl_page *page);
> > -
>
> This line removal is not related to the patch.

Yes, added back.

>
> > -struct sgx_epc_page *sgx_alloc_va_page(void);
> > +struct sgx_epc_page *sgx_alloc_va_page(struct sgx_va_page *va_page);
> > unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page); void
> > sgx_free_va_slot(struct sgx_va_page *va_page, unsigned int offset);
> > bool sgx_va_page_full(struct sgx_va_page *va_page); diff --git
> > a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h index
> > d7a1490d90bb..f8ed9deac18b 100644
> > --- a/arch/x86/kernel/cpu/sgx/sgx.h
> > +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> > @@ -33,7 +33,7 @@ struct sgx_epc_page {
> > unsigned int section;
> > u16 flags;
> > u16 poison;
> > - struct sgx_encl_page *owner;
> > + void *owner;
> > struct list_head list;
> > };
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/encl.c
> > b/arch/x86/kernel/cpu/sgx/encl.c index 68c8d65a8dee..c0725111cc25
> > 100644
> > --- a/arch/x86/kernel/cpu/sgx/encl.c
> > +++ b/arch/x86/kernel/cpu/sgx/encl.c
> > @@ -753,6 +753,7 @@ int sgx_encl_test_and_clear_young(struct
> mm_struct
> > *mm,
> >
> > /**
> > * sgx_alloc_va_page() - Allocate a Version Array (VA) page
> > + * @va_page: struct sgx_va_page connected to this VA page
> > *
> > * Allocate a free EPC page and convert it to a Version Array (VA) page.
> > *
> > @@ -760,12 +761,12 @@ int sgx_encl_test_and_clear_young(struct
> mm_struct *mm,
> > * a VA page,
> > * -errno otherwise
> > */
> > -struct sgx_epc_page *sgx_alloc_va_page(void)
> > +struct sgx_epc_page *sgx_alloc_va_page(struct sgx_va_page *va_page)
> > {
> > struct sgx_epc_page *epc_page;
> > int ret;
> >
> > - epc_page = sgx_alloc_epc_page(NULL, true);
> > + epc_page = sgx_alloc_epc_page(va_page, true);
> > if (IS_ERR(epc_page))
> > return ERR_CAST(epc_page);
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c
> > b/arch/x86/kernel/cpu/sgx/ioctl.c index a4df72f715d7..b77343eb2d49
> > 100644
> > --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> > @@ -30,7 +30,8 @@ static struct sgx_va_page *sgx_encl_grow(struct
> sgx_encl *encl)
> > if (!va_page)
> > return ERR_PTR(-ENOMEM);
> >
> > - va_page->epc_page = sgx_alloc_va_page();
> > + 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);
> > kfree(va_page);
> > --
> > 2.17.1
> >
>
> BR, Jarkko