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Message-Id: <CYU4S0Y9SVZ2.2G9RM5Y3K28XI@suppilovahvero>
Date: Fri, 02 Feb 2024 01:28:32 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Haitao Huang" <haitao.huang@...ux.intel.com>,
<dave.hansen@...ux.intel.com>, <tj@...nel.org>, <mkoutny@...e.com>,
<linux-kernel@...r.kernel.org>, <linux-sgx@...r.kernel.org>,
<x86@...nel.org>, <cgroups@...r.kernel.org>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
<sohil.mehta@...el.com>
Cc: <zhiquan1.li@...el.com>, <kristen@...ux.intel.com>, <seanjc@...gle.com>,
<zhanb@...rosoft.com>, <anakrish@...rosoft.com>,
<mikko.ylinen@...ux.intel.com>, <yangjie@...rosoft.com>,
<chrisyan@...rosoft.com>
Subject: Re: [PATCH v8 05/15] x86/sgx: Add sgx_epc_lru_list to encapsulate
LRU list
On Tue Jan 30, 2024 at 4:09 AM EET, Haitao Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Introduce a data structure to wrap the existing reclaimable list and its
> spinlock. Each cgroup later will have one instance of this structure to
> track EPC pages allocated for processes associated with the same cgroup.
> Just like the global SGX reclaimer (ksgxd), an EPC cgroup reclaims pages
> from the reclaimable list in this structure when its usage reaches near
> its limit.
>
> Use this structure to encapsulate the LRU list and its lock used by the
> global reclaimer.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Co-developed-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
> Co-developed-by: Haitao Huang <haitao.huang@...ux.intel.com>
> Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
I'd put author as last sob but that said I'm not sure if there is rigid
rule to do so. Thus not saying must here.
> Cc: Sean Christopherson <seanjc@...gle.com>
> ---
> V6:
> - removed introduction to unreclaimables in commit message.
>
> V4:
> - Removed unneeded comments for the spinlock and the non-reclaimables.
> (Kai, Jarkko)
> - Revised the commit to add introduction comments for unreclaimables and
> multiple LRU lists.(Kai)
> - Reordered the patches: delay all changes for unreclaimables to
> later, and this one becomes the first change in the SGX subsystem.
>
> V3:
> - Removed the helper functions and revised commit messages.
> ---
> arch/x86/kernel/cpu/sgx/main.c | 39 +++++++++++++++++-----------------
> arch/x86/kernel/cpu/sgx/sgx.h | 15 +++++++++++++
> 2 files changed, 35 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index c32f18b70c73..912959c7ecc9 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -28,10 +28,9 @@ static DEFINE_XARRAY(sgx_epc_address_space);
>
> /*
> * These variables are part of the state of the reclaimer, and must be accessed
> - * with sgx_reclaimer_lock acquired.
> + * with sgx_global_lru.lock acquired.
> */
> -static LIST_HEAD(sgx_active_page_list);
> -static DEFINE_SPINLOCK(sgx_reclaimer_lock);
> +static struct sgx_epc_lru_list sgx_global_lru;
>
> static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
>
> @@ -306,13 +305,13 @@ static void sgx_reclaim_pages(void)
> int ret;
> int i;
>
> - spin_lock(&sgx_reclaimer_lock);
> + spin_lock(&sgx_global_lru.lock);
> for (i = 0; i < SGX_NR_TO_SCAN; i++) {
> - if (list_empty(&sgx_active_page_list))
> + epc_page = list_first_entry_or_null(&sgx_global_lru.reclaimable,
> + struct sgx_epc_page, list);
> + if (!epc_page)
> break;
>
> - epc_page = list_first_entry(&sgx_active_page_list,
> - struct sgx_epc_page, list);
> list_del_init(&epc_page->list);
> encl_page = epc_page->owner;
>
> @@ -324,7 +323,7 @@ static void sgx_reclaim_pages(void)
> */
> epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
> }
> - spin_unlock(&sgx_reclaimer_lock);
> + spin_unlock(&sgx_global_lru.lock);
>
> for (i = 0; i < cnt; i++) {
> epc_page = chunk[i];
> @@ -347,9 +346,9 @@ static void sgx_reclaim_pages(void)
> continue;
>
> skip:
> - spin_lock(&sgx_reclaimer_lock);
> - list_add_tail(&epc_page->list, &sgx_active_page_list);
> - spin_unlock(&sgx_reclaimer_lock);
> + spin_lock(&sgx_global_lru.lock);
> + list_add_tail(&epc_page->list, &sgx_global_lru.reclaimable);
> + spin_unlock(&sgx_global_lru.lock);
>
> kref_put(&encl_page->encl->refcount, sgx_encl_release);
>
> @@ -380,7 +379,7 @@ static void sgx_reclaim_pages(void)
> static bool sgx_should_reclaim(unsigned long watermark)
> {
> return atomic_long_read(&sgx_nr_free_pages) < watermark &&
> - !list_empty(&sgx_active_page_list);
> + !list_empty(&sgx_global_lru.reclaimable);
> }
>
> /*
> @@ -432,6 +431,8 @@ static bool __init sgx_page_reclaimer_init(void)
>
> ksgxd_tsk = tsk;
>
> + sgx_lru_init(&sgx_global_lru);
> +
> return true;
> }
>
> @@ -507,10 +508,10 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void)
> */
> void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
> {
> - spin_lock(&sgx_reclaimer_lock);
> + spin_lock(&sgx_global_lru.lock);
> page->flags |= SGX_EPC_PAGE_RECLAIMER_TRACKED;
> - list_add_tail(&page->list, &sgx_active_page_list);
> - spin_unlock(&sgx_reclaimer_lock);
> + list_add_tail(&page->list, &sgx_global_lru.reclaimable);
> + spin_unlock(&sgx_global_lru.lock);
> }
>
> /**
> @@ -525,18 +526,18 @@ void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
> */
> int sgx_unmark_page_reclaimable(struct sgx_epc_page *page)
> {
> - spin_lock(&sgx_reclaimer_lock);
> + spin_lock(&sgx_global_lru.lock);
> if (page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED) {
> /* The page is being reclaimed. */
> if (list_empty(&page->list)) {
> - spin_unlock(&sgx_reclaimer_lock);
> + spin_unlock(&sgx_global_lru.lock);
> return -EBUSY;
> }
>
> list_del(&page->list);
> page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
> }
> - spin_unlock(&sgx_reclaimer_lock);
> + spin_unlock(&sgx_global_lru.lock);
>
> return 0;
> }
> @@ -578,7 +579,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
> break;
> }
>
> - if (list_empty(&sgx_active_page_list)) {
> + if (list_empty(&sgx_global_lru.reclaimable)) {
> page = ERR_PTR(-ENOMEM);
> break;
> }
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index a898d86dead0..0e99e9ae3a67 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -88,6 +88,21 @@ static inline void *sgx_get_epc_virt_addr(struct sgx_epc_page *page)
> return section->virt_addr + index * PAGE_SIZE;
> }
>
> +/*
> + * Contains EPC pages tracked by the global reclaimer (ksgxd) or an EPC
> + * cgroup.
> + */
> +struct sgx_epc_lru_list {
> + spinlock_t lock;
> + struct list_head reclaimable;
> +};
> +
> +static inline void sgx_lru_init(struct sgx_epc_lru_list *lru)
> +{
> + spin_lock_init(&lru->lock);
> + INIT_LIST_HEAD(&lru->reclaimable);
> +}
> +
> struct sgx_epc_page *__sgx_alloc_epc_page(void);
> void sgx_free_epc_page(struct sgx_epc_page *page);
>
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
BR, Jarkko
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