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

Jarkko Sakkinen
2022-04-21T16:05:37Z

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.

> -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