From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4009CC433EF for ; Mon, 16 May 2022 18:01:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344482AbiEPSBy (ORCPT ); Mon, 16 May 2022 14:01:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343933AbiEPSBv (ORCPT ); Mon, 16 May 2022 14:01:51 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84A4627151; Mon, 16 May 2022 11:01:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0D6C5B815A3; Mon, 16 May 2022 18:01:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53C8AC385AA; Mon, 16 May 2022 18:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652724107; bh=gGGp96fpNS19tUQwrmfC7XaxkZf7UdGzL+noF9M+JsE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MiX25ez2C4cC7B6yYgECK7imNKYWEr2tnZ7CvZRTSkYcrM5/NKLvHOUuq2eQD7HEA LVDp+KSrjVfrvQcIklcoEhhV8E8ExoZkKXq4LOrRaLod4JC4jKQKu95v/LS/xEWwct KXjmQl3f9dZWoHVtVz/NGsTd6m2fZdJevrBaovaWEtA9BuNWc7e7Feo+aDtxiLwYDX ZC00Xcf7JW/f0OpeCxuyYFbLM2JwoIl5V+IMmKPt1VOS+scZUHYDqVh5op6n5YZLzB nZhEIEyKHeDk97DELMfKTOmRS8S+TEJvvt2RKy7i/nLRc3nPAolDgFsVfSv3g11Mms FnHsJ8ovtEZ2w== Date: Mon, 16 May 2022 21:00:12 +0300 From: Jarkko Sakkinen To: Kristen Carlson Accardi Cc: linux-sgx@vger.kernel.org, Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] x86/sgx: Set active memcg prior to shmem allocation Message-ID: References: <20220516172523.5113-1-kristen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220516172523.5113-1-kristen@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 16, 2022 at 10:25:22AM -0700, Kristen Carlson Accardi wrote: > When the system runs out of enclave memory, SGX can reclaim EPC pages > by swapping to normal RAM. These backing pages are allocated via a > per-enclave shared memory area. Since SGX allows unlimited over > commit on EPC memory, the reclaimer thread can allocate a large > number of backing RAM pages in response to EPC memory pressure. > > When the shared memory backing RAM allocation occurs during > the reclaimer thread context, the shared memory is charged to > the root memory control group, and the shmem usage of the enclave > is not properly accounted for, making cgroups ineffective at > limiting the amount of RAM an enclave can consume. > > For example, when using a cgroup to launch a set of test > enclaves, the kernel does not properly account for 50% - 75% of > shmem page allocations on average. In the worst case, when > nearly all allocations occur during the reclaimer thread, the > kernel accounts less than a percent of the amount of shmem used > by the enclave's cgroup to the correct cgroup. > > SGX currently stores a list of mm_structs that are associated with > an enclave. In order to allow the enclave's cgroup to more accurately > reflect the shmem usage, the memory control group (struct mem_cgroup) > of one of these mm_structs can be set as the active memory cgroup > prior to allocating any EPC backing pages. This will make any shmem > allocations be charged to a memory control group associated with the > enclave's cgroup. This will allow memory cgroup limits to restrict > RAM usage more effectively. > > This patch will create a new function - sgx_encl_alloc_backing(). > This function will be used whenever a new backing storage page > needs to be allocated. Previously the same function was used for > page allocation as well as retrieving a previously allocated page. > Prior to backing page allocation, if there is a mm_struct associated > with the enclave that is requesting the allocation, it will be set > as the active memory control group. > > Signed-off-by: Kristen Carlson Accardi > --- > arch/x86/kernel/cpu/sgx/encl.c | 89 +++++++++++++++++++++++++++++++++- > arch/x86/kernel/cpu/sgx/encl.h | 6 ++- > arch/x86/kernel/cpu/sgx/main.c | 4 +- > 3 files changed, 93 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c > index 001808e3901c..fa017bc4f99e 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -32,7 +32,7 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, > else > page_index = PFN_DOWN(encl->size); > > - ret = sgx_encl_get_backing(encl, page_index, &b); > + ret = sgx_encl_lookup_backing(encl, page_index, &b); > if (ret) > return ret; > > @@ -574,7 +574,7 @@ static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl, > * 0 on success, > * -errno otherwise. > */ > -int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, > +static int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, > struct sgx_backing *backing) > { > pgoff_t pcmd_index = PFN_DOWN(encl->size) + 1 + (page_index >> 5); > @@ -601,6 +601,91 @@ int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, > return 0; > } > > +static struct mem_cgroup * sgx_encl_set_active_memcg(struct sgx_encl *encl) > +{ > + struct mm_struct *mm = current->mm; > + struct sgx_encl_mm *encl_mm; > + struct mem_cgroup *memcg; > + int idx; > + > + memcg = get_mem_cgroup_from_mm(mm); > + Inline comment right here, describing the "fast path". > + if (mm) > + return memcg; > + And another here, describing the "slow path" > + idx = srcu_read_lock(&encl->srcu); > + > + list_for_each_entry_rcu(encl_mm, &encl->mm_list, list) { > + if (encl_mm->mm == NULL) > + continue; > + > + mm = encl_mm->mm; > + break; > + > + } > + > + srcu_read_unlock(&encl->srcu, idx); > + > + if (!mm) > + return memcg; > + > + memcg = get_mem_cgroup_from_mm(mm); > + > + return set_active_memcg(memcg); > +} > + > +/** > + * sgx_encl_alloc_backing() - allocate a new backing storage page > + * @encl: an enclave pointer > + * @page_index: enclave page index > + * @backing: data for accessing backing storage for the page > + * > + * If this function is called from the kernel thread, it will set > + * the active memcg to one of the enclaves mm's in order to ensure > + * that shmem page allocations are charged to the enclave when they > + * are retrieved. Upon exit, the old memcg (if it existed at all) > + * will be restored. > + * > + * Return: > + * 0 on success, > + * -errno otherwise. > + */ > +int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index, > + struct sgx_backing *backing) > +{ > + struct mem_cgroup *old_memcg; > + int ret; > + > + old_memcg = sgx_encl_set_active_memcg(encl); > + > + ret = sgx_encl_get_backing(encl, page_index, backing); > + > + set_active_memcg(old_memcg); > + > + return ret; > +} > + > +/** > + * sgx_encl_lookup_backing() - retrieve an existing backing storage page > + * @encl: an enclave pointer > + * @page_index: enclave page index > + * @backing: data for accessing backing storage for the page > + * > + * Retrieve a backing page for loading data back into an EPC page with ELDU. > + * It is the caller's responsibility to ensure that it is appropriate to use > + * sgx_encl_lookup_backing() rather than sgx_encl_alloc_backing(). If lookup is > + * not used correctly, this will cause an allocation which is not accounted for. > + * > + * Return: > + * 0 on success, > + * -errno otherwise. > + */ > +int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index, > + struct sgx_backing *backing) > +{ > + return sgx_encl_get_backing(encl, page_index, backing); > +} > + > /** > * sgx_encl_put_backing() - Unpin the backing storage > * @backing: data for accessing backing storage for the page > diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h > index fec43ca65065..7816cfe8f832 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.h > +++ b/arch/x86/kernel/cpu/sgx/encl.h > @@ -105,8 +105,10 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start, > > void sgx_encl_release(struct kref *ref); > int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm); > -int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, > - struct sgx_backing *backing); > +int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_index, > + struct sgx_backing *backing); > +int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long page_index, > + struct sgx_backing *backing); > 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); > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index 4b41efc9e367..7d41c8538795 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -310,7 +310,7 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page, > encl->secs_child_cnt--; > > if (!encl->secs_child_cnt && test_bit(SGX_ENCL_INITIALIZED, &encl->flags)) { > - ret = sgx_encl_get_backing(encl, PFN_DOWN(encl->size), > + ret = sgx_encl_alloc_backing(encl, PFN_DOWN(encl->size), > &secs_backing); > if (ret) > goto out; > @@ -381,7 +381,7 @@ static void sgx_reclaim_pages(void) > goto skip; > > page_index = PFN_DOWN(encl_page->desc - encl_page->encl->base); > - ret = sgx_encl_get_backing(encl_page->encl, page_index, &backing[i]); > + ret = sgx_encl_alloc_backing(encl_page->encl, page_index, &backing[i]); > if (ret) > goto skip; > > -- > 2.20.1 > BR, Jarkko