Re: [PATCH v4 06/18] x86/sgx: Introduce EPC page states

Jarkko Sakkinen
2023-09-13T15:15:55Z

On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> Use the lower 3 bits in the flags field of sgx_epc_page struct to
> track EPC states in its life cycle and define an enum for possible
> states. More state(s) will be added later.
>
> Signed-off-by: Haitao Huang <haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> ---
> V4:
> - No changes other than required for patch reordering.
>
> V3:
> - This is new in V3 to replace the bit mask based approach (requested by Jarkko)
> ---
> arch/x86/kernel/cpu/sgx/encl.c | 14 +++++++---
> arch/x86/kernel/cpu/sgx/ioctl.c | 7 +++--
> arch/x86/kernel/cpu/sgx/main.c | 19 +++++++------
> arch/x86/kernel/cpu/sgx/sgx.h | 49 ++++++++++++++++++++++++++++++---
> 4 files changed, 71 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index f84ee2eeb058..d11d4111aa98 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -244,8 +244,12 @@ static struct sgx_epc_page *sgx_encl_load_secs(struct sgx_encl *encl)
> {
> struct sgx_epc_page *epc_page = encl->secs.epc_page;
>
> - if (!epc_page)
> + if (!epc_page) {
> epc_page = sgx_encl_eldu(&encl->secs, NULL);
> + if (!IS_ERR(epc_page))
> + sgx_record_epc_page(epc_page,
> + SGX_EPC_PAGE_UNRECLAIMABLE);

sgx_record_epc_page(epc_page, SGX_EPC_PAGE_UNRECLAIMABLE) ;

> + }
>
> return epc_page;
> }
> @@ -273,7 +277,7 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
>
> encl->secs_child_cnt++;
> sgx_record_epc_page(epc_page,
> - SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + SGX_EPC_PAGE_RECLAIMABLE);
>
> return entry;
> }
> @@ -400,7 +404,7 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
> encl->secs_child_cnt++;
>
> sgx_record_epc_page(epc_page,
> - SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + SGX_EPC_PAGE_RECLAIMABLE);
>
> phys_addr = sgx_get_epc_phys_addr(epc_page);
> /*
> @@ -1258,6 +1262,8 @@ struct sgx_epc_page *sgx_alloc_va_page(bool reclaim)
> sgx_encl_free_epc_page(epc_page);
> return ERR_PTR(-EFAULT);
> }
> + sgx_record_epc_page(epc_page,
> + SGX_EPC_PAGE_UNRECLAIMABLE);
>
> return epc_page;
> }
> @@ -1317,7 +1323,7 @@ void sgx_encl_free_epc_page(struct sgx_epc_page *page)
> {
> int ret;
>
> - WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_STATE_MASK);
>
> ret = __eremove(sgx_get_epc_virt_addr(page));
> if (WARN_ONCE(ret, EREMOVE_ERROR_MESSAGE, ret, ret))
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 0d79dec408af..c28f074d5d71 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -113,6 +113,9 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
> encl->attributes = secs->attributes;
> encl->attributes_mask = SGX_ATTR_UNPRIV_MASK;
>
> + sgx_record_epc_page(encl->secs.epc_page,
> + SGX_EPC_PAGE_UNRECLAIMABLE);
> +
> /* Set only after completion, as encl->lock has not been taken. */
> set_bit(SGX_ENCL_CREATED, &encl->flags);
>
> @@ -323,7 +326,7 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
> }
>
> sgx_record_epc_page(epc_page,
> - SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + SGX_EPC_PAGE_RECLAIMABLE);
> mutex_unlock(&encl->lock);
> mmap_read_unlock(current->mm);
> return ret;
> @@ -978,7 +981,7 @@ static long sgx_enclave_modify_types(struct sgx_encl *encl,
> mutex_lock(&encl->lock);
>
> sgx_record_epc_page(entry->epc_page,
> - SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + SGX_EPC_PAGE_RECLAIMABLE);
> }
>
> /* Change EPC type */
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index dec1d57cbff6..b26860399402 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -318,7 +318,7 @@ static void sgx_reclaim_pages(void)
> /* The owner is freeing the page. No need to add the
> * page back to the list of reclaimable pages.
> */
> - epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
> + sgx_epc_page_reset_state(epc_page);
> }
> spin_unlock(&sgx_global_lru.lock);
>
> @@ -344,6 +344,7 @@ static void sgx_reclaim_pages(void)
>
> skip:
> spin_lock(&sgx_global_lru.lock);
> + sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIMABLE);
> list_add_tail(&epc_page->list, &sgx_global_lru.reclaimable);
> spin_unlock(&sgx_global_lru.lock);
>
> @@ -367,7 +368,7 @@ static void sgx_reclaim_pages(void)
> sgx_reclaimer_write(epc_page, &backing[i]);
>
> kref_put(&encl_page->encl->refcount, sgx_encl_release);
> - epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
> + sgx_epc_page_reset_state(epc_page);
>
> sgx_free_epc_page(epc_page);
> }
> @@ -507,9 +508,9 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void)
> void sgx_record_epc_page(struct sgx_epc_page *page, unsigned long flags)
> {
> spin_lock(&sgx_global_lru.lock);
> - WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
> + WARN_ON_ONCE(sgx_epc_page_reclaimable(page->flags));
> page->flags |= flags;
> - if (flags & SGX_EPC_PAGE_RECLAIMER_TRACKED)
> + if (sgx_epc_page_reclaimable(flags))
> list_add_tail(&page->list, &sgx_global_lru.reclaimable);
> spin_unlock(&sgx_global_lru.lock);
> }
> @@ -527,7 +528,7 @@ void sgx_record_epc_page(struct sgx_epc_page *page, unsigned long flags)
> int sgx_drop_epc_page(struct sgx_epc_page *page)
> {
> spin_lock(&sgx_global_lru.lock);
> - if (page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED) {
> + if (sgx_epc_page_reclaimable(page->flags)) {
> /* The page is being reclaimed. */
> if (list_empty(&page->list)) {
> spin_unlock(&sgx_global_lru.lock);
> @@ -535,7 +536,7 @@ int sgx_drop_epc_page(struct sgx_epc_page *page)
> }
>
> list_del(&page->list);
> - page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
> + sgx_epc_page_reset_state(page);
> }
> spin_unlock(&sgx_global_lru.lock);
>
> @@ -607,6 +608,8 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
> struct sgx_epc_section *section = &sgx_epc_sections[page->section];
> struct sgx_numa_node *node = section->node;
>
> + WARN_ON_ONCE(page->flags & (SGX_EPC_PAGE_STATE_MASK));
> +
> spin_lock(&node->lock);
>
> page->owner = NULL;
> @@ -614,7 +617,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
> list_add(&page->list, &node->sgx_poison_page_list);
> else
> list_add_tail(&page->list, &node->free_page_list);
> - page->flags = SGX_EPC_PAGE_IS_FREE;
> + page->flags = SGX_EPC_PAGE_FREE;
>
> spin_unlock(&node->lock);
> atomic_long_inc(&sgx_nr_free_pages);
> @@ -715,7 +718,7 @@ int arch_memory_failure(unsigned long pfn, int flags)
> * If the page is on a free list, move it to the per-node
> * poison page list.
> */
> - if (page->flags & SGX_EPC_PAGE_IS_FREE) {
> + if (page->flags == SGX_EPC_PAGE_FREE) {
> list_move(&page->list, &node->sgx_poison_page_list);
> goto out;
> }
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index 113d930fd087..2faeb40b345f 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -23,11 +23,36 @@
> #define SGX_NR_LOW_PAGES 32
> #define SGX_NR_HIGH_PAGES 64
>
> -/* Pages, which are being tracked by the page reclaimer. */
> -#define SGX_EPC_PAGE_RECLAIMER_TRACKED BIT(0)
> +enum sgx_epc_page_state {
> + /* Not tracked by the reclaimer:
> + * Pages allocated for virtual EPC which are never tracked by the host
> + * reclaimer; pages just allocated from free list but not yet put in
> + * use; pages just reclaimed, but not yet returned to the free list.
> + * Becomes FREE after sgx_free_epc()
> + * Becomes RECLAIMABLE or UNRECLAIMABLE after sgx_record_epc()
> + */
> + SGX_EPC_PAGE_NOT_TRACKED = 0,
> +
> + /* Page is in the free list, ready for allocation
> + * Becomes NOT_TRACKED after sgx_alloc_epc_page()
> + */
> + SGX_EPC_PAGE_FREE = 1,
> +
> + /* Page is in use and tracked in a reclaimable LRU list
> + * Becomes NOT_TRACKED after sgx_drop_epc()
> + */
> + SGX_EPC_PAGE_RECLAIMABLE = 2,
> +
> + /* Page is in use but tracked in an unreclaimable LRU list. These are
> + * only reclaimable when the whole enclave is OOM killed or the enclave
> + * is released, e.g., VA, SECS pages
> + * Becomes NOT_TRACKED after sgx_drop_epc()
> + */
> + SGX_EPC_PAGE_UNRECLAIMABLE = 3,
>
> -/* Pages on free list */
> -#define SGX_EPC_PAGE_IS_FREE BIT(1)
> +};
> +
> +#define SGX_EPC_PAGE_STATE_MASK GENMASK(2, 0)
>
> struct sgx_epc_page {
> unsigned int section;
> @@ -37,6 +62,22 @@ struct sgx_epc_page {
> struct list_head list;
> };
>
> +static inline void sgx_epc_page_reset_state(struct sgx_epc_page *page)
> +{
> + page->flags &= ~SGX_EPC_PAGE_STATE_MASK;
> +}
> +
> +static inline void sgx_epc_page_set_state(struct sgx_epc_page *page, unsigned long flags)
> +{
> + page->flags &= ~SGX_EPC_PAGE_STATE_MASK;
> + page->flags |= (flags & SGX_EPC_PAGE_STATE_MASK);
> +}
> +
> +static inline bool sgx_epc_page_reclaimable(unsigned long flags)
> +{
> + return SGX_EPC_PAGE_RECLAIMABLE == (flags & SGX_EPC_PAGE_STATE_MASK);
> +}
> +
> /*
> * Contains the tracking data for NUMA nodes having EPC pages. Most importantly,
> * the free page list local to the node is stored here.
> --
> 2.25.1

BR, Jarkko