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    Subject[PATCH v11 12/14] x86/sgx: Turn on per-cgroup EPC reclamation
    Date
    From: Kristen Carlson Accardi <kristen@linux.intel.com>

    Previous patches have implemented all infrastructure needed for
    per-cgroup EPC page tracking and reclaiming. But all reclaimable EPC
    pages are still tracked in the global LRU as sgx_lru_list() returns hard
    coded reference to the global LRU.

    Change sgx_lru_list() to return the LRU of the cgroup in which the given
    EPC page is allocated.

    This makes all EPC pages tracked in per-cgroup LRUs and the global
    reclaimer (ksgxd) will not be able to reclaim any pages from the global
    LRU. However, in cases of over-committing, i.e., the sum of cgroup
    limits greater than the total capacity, cgroups may never reclaim but
    the total usage can still be near the capacity. Therefore a global
    reclamation is still needed in those cases and it should be performed
    from the root cgroup.

    Modify sgx_reclaim_pages_global(), to reclaim from the root EPC cgroup
    when cgroup is enabled, otherwise from the global LRU. Export
    sgx_cgroup_reclaim_pages() in the header file so it can be reused for
    this purpose.

    Similarly, modify sgx_can_reclaim(), to check emptiness of LRUs of all
    cgroups when EPC cgroup is enabled, otherwise only check the global LRU.
    Export sgx_cgroup_lru_empty() so it can be reused for this purpose.

    Finally, change sgx_reclaim_direct(), to check and ensure there are free
    pages at cgroup level so forward progress can be made by the caller.
    Export sgx_cgroup_should_reclaim() for reuse.

    With these changes, the global reclamation and per-cgroup reclamation
    both work properly with all pages tracked in per-cgroup LRUs.

    Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
    Co-developed-by: Haitao Huang <haitao.huang@linux.intel.com>
    Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
    ---
    V11:
    - Reword the comments for global reclamation for allocation failure
    after passing cgroup charging. (Kai)
    - Add stub functions to remove ifdefs in c file (Kai)
    - Add more detailed comments to clarify each page belongs to one cgroup, or the
    root. (Kai)

    V10:
    - Add comment to clarify each page belongs to one cgroup, or the root by
    default. (Kai)
    - Merge the changes that expose sgx_cgroup_* functions to this patch.
    - Add changes for sgx_reclaim_direct() that was missed previously.

    V7:
    - Split this out from the big patch, #10 in V6. (Dave, Kai)
    ---
    arch/x86/kernel/cpu/sgx/epc_cgroup.c | 6 ++--
    arch/x86/kernel/cpu/sgx/epc_cgroup.h | 27 +++++++++++++++++
    arch/x86/kernel/cpu/sgx/main.c | 43 ++++++++++++++++++++++++++--
    3 files changed, 71 insertions(+), 5 deletions(-)

    diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.c b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
    index 2efc33476b0b..16fe0e1574ec 100644
    --- a/arch/x86/kernel/cpu/sgx/epc_cgroup.c
    +++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
    @@ -68,7 +68,7 @@ static inline u64 sgx_cgroup_max_pages_to_root(struct sgx_cgroup *sgx_cg)
    *
    * Return: %true if all cgroups under the specified root have empty LRU lists.
    */
    -static bool sgx_cgroup_lru_empty(struct misc_cg *root)
    +bool sgx_cgroup_lru_empty(struct misc_cg *root)
    {
    struct cgroup_subsys_state *css_root;
    struct cgroup_subsys_state *pos;
    @@ -116,7 +116,7 @@ static bool sgx_cgroup_lru_empty(struct misc_cg *root)
    * the LRUs are recently accessed, i.e., considered "too young" to reclaim, no
    * page will actually be reclaimed after walking the whole tree.
    */
    -static void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
    +void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
    {
    struct cgroup_subsys_state *css_root;
    struct cgroup_subsys_state *pos;
    @@ -157,7 +157,7 @@ static void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *cha
    * threshold (%SGX_CG_MIN_FREE_PAGE) and there are reclaimable pages within the
    * cgroup.
    */
    -static bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
    +bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
    {
    u64 cur, max;

    diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.h b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
    index 9a2d51a91e5c..963aa19d3c47 100644
    --- a/arch/x86/kernel/cpu/sgx/epc_cgroup.h
    +++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
    @@ -13,6 +13,11 @@
    #define MISC_CG_RES_SGX_EPC MISC_CG_RES_TYPES
    struct sgx_cgroup;

    +static inline struct misc_cg *misc_from_sgx(struct sgx_cgroup *sgx_cg)
    +{
    + return NULL;
    +}
    +
    static inline struct sgx_cgroup *sgx_get_current_cg(void)
    {
    return NULL;
    @@ -27,8 +32,22 @@ static inline int sgx_cgroup_try_charge(struct sgx_cgroup *sgx_cg, enum sgx_recl

    static inline void sgx_cgroup_uncharge(struct sgx_cgroup *sgx_cg) { }

    +static inline bool sgx_cgroup_lru_empty(struct misc_cg *root)
    +{
    + return true;
    +}
    +
    +static inline bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
    +{
    + return false;
    +}
    +
    static inline void sgx_cgroup_init(void) { }

    +static inline void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
    +{
    +}
    +
    #else

    struct sgx_cgroup {
    @@ -37,6 +56,11 @@ struct sgx_cgroup {
    struct work_struct reclaim_work;
    };

    +static inline struct misc_cg *misc_from_sgx(struct sgx_cgroup *sgx_cg)
    +{
    + return sgx_cg->cg;
    +}
    +
    static inline struct sgx_cgroup *sgx_cgroup_from_misc_cg(struct misc_cg *cg)
    {
    return (struct sgx_cgroup *)(cg->res[MISC_CG_RES_SGX_EPC].priv);
    @@ -67,6 +91,9 @@ static inline void sgx_put_cg(struct sgx_cgroup *sgx_cg)

    int sgx_cgroup_try_charge(struct sgx_cgroup *sgx_cg, enum sgx_reclaim reclaim);
    void sgx_cgroup_uncharge(struct sgx_cgroup *sgx_cg);
    +bool sgx_cgroup_lru_empty(struct misc_cg *root);
    +bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg);
    +void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm);
    void sgx_cgroup_init(void);

    #endif
    diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
    index 11edbdb06782..e42e4a972752 100644
    --- a/arch/x86/kernel/cpu/sgx/main.c
    +++ b/arch/x86/kernel/cpu/sgx/main.c
    @@ -32,9 +32,30 @@ static DEFINE_XARRAY(sgx_epc_address_space);
    */
    static struct sgx_epc_lru_list sgx_global_lru;

    +/*
    + * Get the per-cgroup or global LRU list that tracks the given reclaimable page.
    + */
    static inline struct sgx_epc_lru_list *sgx_lru_list(struct sgx_epc_page *epc_page)
    {
    +#ifdef CONFIG_CGROUP_SGX_EPC
    + /*
    + * epc_page->sgx_cg here is never NULL during a reclaimable epc_page's
    + * life between sgx_alloc_epc_page() and sgx_free_epc_page():
    + *
    + * In sgx_alloc_epc_page(), epc_page->sgx_cg is set to the return from
    + * sgx_get_current_cg() which is the misc cgroup of the current task, or
    + * the root by default even if the misc cgroup is disabled by kernel
    + * command line.
    + *
    + * epc_page->sgx_cg is only unset by sgx_free_epc_page().
    + *
    + * This function is never used before sgx_alloc_epc_page() or after
    + * sgx_free_epc_page().
    + */
    + return &epc_page->sgx_cg->lru;
    +#else
    return &sgx_global_lru;
    +#endif
    }

    /*
    @@ -42,7 +63,8 @@ static inline struct sgx_epc_lru_list *sgx_lru_list(struct sgx_epc_page *epc_pag
    */
    static inline bool sgx_can_reclaim(void)
    {
    - return !list_empty(&sgx_global_lru.reclaimable);
    + return !sgx_cgroup_lru_empty(misc_cg_root()) ||
    + !list_empty(&sgx_global_lru.reclaimable);
    }

    static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
    @@ -404,7 +426,10 @@ static bool sgx_should_reclaim(unsigned long watermark)

    static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
    {
    - sgx_reclaim_pages(&sgx_global_lru, charge_mm);
    + if (IS_ENABLED(CONFIG_CGROUP_SGX_EPC))
    + sgx_cgroup_reclaim_pages(misc_cg_root(), charge_mm);
    + else
    + sgx_reclaim_pages(&sgx_global_lru, charge_mm);
    }

    /*
    @@ -414,6 +439,14 @@ static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
    */
    void sgx_reclaim_direct(void)
    {
    + struct sgx_cgroup *sgx_cg = sgx_get_current_cg();
    +
    + /* Make sure there are some free pages at cgroup level */
    + if (sgx_cg && sgx_cgroup_should_reclaim(sgx_cg)) {
    + sgx_cgroup_reclaim_pages(misc_from_sgx(sgx_cg), current->mm);
    + sgx_put_cg(sgx_cg);
    + }
    + /* Make sure there are some free pages at global level */
    if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
    sgx_reclaim_pages_global(current->mm);
    }
    @@ -616,6 +649,12 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, enum sgx_reclaim reclaim)
    break;
    }

    + /*
    + * At this point, the usage within this cgroup is under its
    + * limit but there is no physical page left for allocation.
    + * Perform a global reclaim to get some pages released from any
    + * cgroup with reclaimable pages.
    + */
    sgx_reclaim_pages_global(current->mm);
    cond_resched();
    }
    --
    2.25.1

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