Re: [PATCH v4 15/18] x86/sgx: Prepare for multiple LRUs

Jarkko Sakkinen
2023-09-13T15:42:52Z

On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> Add sgx_can_reclaim() wrapper and encapsulate direct references to the
> global LRU list in the reclaimer functions so that they can be called with
> an LRU list per EPC cgroup.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Signed-off-by: Haitao Huang <haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Cc: Sean Christopherson <seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> ---
> V4:
> - Re-organized this patch to include all changes related to
> encapsulation of the global LRU
> - Moved this patch to precede the EPC cgroup patch
> ---
> arch/x86/kernel/cpu/sgx/main.c | 41 +++++++++++++++++++++++-----------
> 1 file changed, 28 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index ce316bd5e5bb..3d396fe5ec09 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -34,6 +34,16 @@ static DEFINE_XARRAY(sgx_epc_address_space);
> */
> static struct sgx_epc_lru_lists sgx_global_lru;
>
> +static inline struct sgx_epc_lru_lists *sgx_lru_lists(struct sgx_epc_page *epc_page)
> +{
> + return &sgx_global_lru;
> +}

I'd simply export sgx_global_lru.

> +static inline bool sgx_can_reclaim(void)
> +{
> + return !list_empty(&sgx_global_lru.reclaimable);
> +}

Accessors for the object should be named so that this fact is reflected,
e.g. sgx_global_lru_can_reclaim() in this case.

I would just open code this to the call sites though.

> +
> static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
>
> /* Nodes with one or more EPC sections. */
> @@ -339,6 +349,7 @@ size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
> struct sgx_backing backing[SGX_NR_TO_SCAN_MAX];
> struct sgx_epc_page *epc_page, *tmp;
> struct sgx_encl_page *encl_page;
> + struct sgx_epc_lru_lists *lru;
> pgoff_t page_index;
> LIST_HEAD(iso);
> size_t ret;
> @@ -372,10 +383,11 @@ size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
> continue;
>
> skip:
> - spin_lock(&sgx_global_lru.lock);
> + lru = sgx_lru_lists(epc_page);
> + spin_lock(&lru->lock);
> sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIMABLE);
> - list_move_tail(&epc_page->list, &sgx_global_lru.reclaimable);
> - spin_unlock(&sgx_global_lru.lock);
> + list_move_tail(&epc_page->list, &lru->reclaimable);
> + spin_unlock(&lru->lock);
>
> kref_put(&encl_page->encl->refcount, sgx_encl_release);
> }
> @@ -399,7 +411,7 @@ size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
> static bool sgx_should_reclaim(unsigned long watermark)
> {
> return atomic_long_read(&sgx_nr_free_pages) < watermark &&
> - !list_empty(&sgx_global_lru.reclaimable);
> + sgx_can_reclaim();
> }
>
> /*
> @@ -529,14 +541,16 @@ 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);
> + struct sgx_epc_lru_lists *lru = sgx_lru_lists(page);
> +
> + spin_lock(&lru->lock);
> WARN_ON_ONCE(sgx_epc_page_reclaimable(page->flags));
> page->flags |= flags;
> if (sgx_epc_page_reclaimable(flags))
> - list_add_tail(&page->list, &sgx_global_lru.reclaimable);
> + list_add_tail(&page->list, &lru->reclaimable);
> else
> - list_add_tail(&page->list, &sgx_global_lru.unreclaimable);
> - spin_unlock(&sgx_global_lru.lock);
> + list_add_tail(&page->list, &lru->unreclaimable);
> + spin_unlock(&lru->lock);
> }
>
> /**
> @@ -551,15 +565,16 @@ 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);
> + struct sgx_epc_lru_lists *lru = sgx_lru_lists(page);
> +
> + spin_lock(&lru->lock);
> if (sgx_epc_page_reclaim_in_progress(page->flags)) {
> - spin_unlock(&sgx_global_lru.lock);
> + spin_unlock(&lru->lock);
> return -EBUSY;
> }
> -
> list_del(&page->list);
> sgx_epc_page_reset_state(page);
> - spin_unlock(&sgx_global_lru.lock);
> + spin_unlock(&lru->lock);
>
> return 0;
> }
> @@ -592,7 +607,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
> break;
> }
>
> - if (list_empty(&sgx_global_lru.reclaimable))
> + if (!sgx_can_reclaim())
> return ERR_PTR(-ENOMEM);
>
> if (!reclaim) {
> --
> 2.25.1

BR, Jarkko