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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EDB9C2D0E2 for ; Tue, 22 Sep 2020 10:45:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D21FE2073A for ; Tue, 22 Sep 2020 10:45:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="E3uvcZBI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726461AbgIVKpq (ORCPT ); Tue, 22 Sep 2020 06:45:46 -0400 Received: from mail.skyhub.de ([5.9.137.197]:56408 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726423AbgIVKpq (ORCPT ); Tue, 22 Sep 2020 06:45:46 -0400 Received: from zn.tnic (p200300ec2f0bfb00b5db4aa9bc6d967b.dip0.t-ipconnect.de [IPv6:2003:ec:2f0b:fb00:b5db:4aa9:bc6d:967b]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 13FE41EC0114; Tue, 22 Sep 2020 12:45:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1600771544; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=KV+AIznwncL3m4lCijPPkTe9M8NJxOjO/EQJQDekkzE=; b=E3uvcZBIX6xBAvVy9ljLvAVUwswlqj57o9mJK528BSkjPOEW6tf+TrwfVpMFrF+/P2CnV0 H6K2W7hIwVrk9gjxW9Je7Ydj/CWa1UabCXdsDbofeH4NdZIAyl74m5Rh4ke89D5PUfFhz4 wFiqD32dr0Ktwx9duXavENPjkaxmAlQ= Date: Tue, 22 Sep 2020 12:45:38 +0200 From: Borislav Petkov To: Jarkko Sakkinen Cc: x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jethro Beekman , Jordan Hand , Nathaniel McCallum , Chunyang Hui , Seth Moore , Sean Christopherson , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com Subject: Re: [PATCH v38 16/24] x86/sgx: Add a page reclaimer Message-ID: <20200922104538.GE22660@zn.tnic> References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> <20200915112842.897265-17-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200915112842.897265-17-jarkko.sakkinen@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Sep 15, 2020 at 02:28:34PM +0300, Jarkko Sakkinen wrote: > There is a limited amount of EPC available. Therefore, some of it must be > copied to the regular memory, and only subset kept in the SGX reserved > memory. While kernel cannot directly access enclave memory, SGX provides a > set of ENCLS leaf functions to perform reclaiming. > > This commits implements a page reclaimer by using these leaf functions. It s/This commits implements/Implement/ > picks the victim pages in LRU fashion from all the enclaves running in the > system. The thread ksgxswapd reclaims pages on the event when the number of > free EPC pages goes below SGX_NR_LOW_PAGES up until it reaches > SGX_NR_HIGH_PAGES. ... Had to grep the SDM for that "eldu" magic. It could use a comment: /* * ELDU: Load an EPC page as unblocked. For more info, see "OS * Management of EPC Pages" in the SDM. */ or so, to denote what's going on here. > +static struct sgx_epc_page *sgx_encl_eldu(struct sgx_encl_page *encl_page, > + struct sgx_epc_page *secs_page) > +{ > + unsigned long va_offset = SGX_ENCL_PAGE_VA_OFFSET(encl_page); > + struct sgx_encl *encl = encl_page->encl; > + struct sgx_epc_page *epc_page; > + int ret; > + > + epc_page = sgx_alloc_epc_page(encl_page, false); > + if (IS_ERR(epc_page)) > + return epc_page; > + > + ret = __sgx_encl_eldu(encl_page, epc_page, secs_page); > + if (ret) { > + sgx_free_epc_page(epc_page); > + return ERR_PTR(ret); > + } > + > + sgx_free_va_slot(encl_page->va_page, va_offset); > + list_move(&encl_page->va_page->list, &encl->va_pages); > + encl_page->desc &= ~SGX_ENCL_PAGE_VA_OFFSET_MASK; > + encl_page->epc_page = epc_page; > + > + return epc_page; > +} ... > diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h > index 0448d22d3010..11dcf4e7fb3e 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.h > +++ b/arch/x86/kernel/cpu/sgx/encl.h > @@ -19,6 +19,10 @@ > > /** > * enum sgx_encl_page_desc - defines bits for an enclave page's descriptor > + * %SGX_ENCL_PAGE_RECLAIMED: The page is in the process of being > + * reclaimed. SGX_ENCL_PAGE_RECLAIMED means, tho, that the page has been reclaimed already. I guess that reads better: + if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED) + return ERR_PTR(-EBUSY); > + * %SGX_ENCL_PAGE_VA_OFFSET_MASK: Holds the offset in the Version Array > + * (VA) page for a swapped page. > * %SGX_ENCL_PAGE_ADDR_MASK: Holds the virtual address of the page. > * > * The page address for SECS is zero and is used by the subsystem to recognize ... > @@ -86,24 +123,34 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > { > unsigned long encl_size = secs->size + PAGE_SIZE; > struct sgx_epc_page *secs_epc; > + struct sgx_va_page *va_page; > struct sgx_pageinfo pginfo; > struct sgx_secinfo secinfo; > struct file *backing; > long ret; > > + va_page = sgx_encl_grow(encl); > + if (IS_ERR(va_page)) > + return PTR_ERR(va_page); > + else if (va_page) Not "else" simply? AFAICT, sgx_encl_grow() would either return an ERR_PTR or the actual page... Also, should the growing happen *after* the SECS validation? > + list_add(&va_page->list, &encl->va_pages); > + > if (sgx_validate_secs(secs)) { > pr_debug("invalid SECS\n"); > - return -EINVAL; > + ret = -EINVAL; > + goto err_out_shrink; > } > > backing = shmem_file_setup("SGX backing", encl_size + (encl_size >> 5), > VM_NORESERVE); > - if (IS_ERR(backing)) > - return PTR_ERR(backing); > + if (IS_ERR(backing)) { > + ret = PTR_ERR(backing); > + goto err_out_shrink; > + } > > encl->backing = backing; > > - secs_epc = __sgx_alloc_epc_page(); > + secs_epc = sgx_alloc_epc_page(&encl->secs, true); > if (IS_ERR(secs_epc)) { > ret = PTR_ERR(secs_epc); > goto err_out_backing; > @@ -151,6 +198,9 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > fput(encl->backing); > encl->backing = NULL; > > +err_out_shrink: > + sgx_encl_shrink(encl, va_page); > + > return ret; > } ... Let's add some comment blurb about "Write back/invalidate an EPC page" to at least start to explain what that "ewb" is. > +static void sgx_encl_ewb(struct sgx_epc_page *epc_page, > + struct sgx_backing *backing) > +{ > + struct sgx_encl_page *encl_page = epc_page->owner; > + struct sgx_encl *encl = encl_page->encl; > + struct sgx_va_page *va_page; > + unsigned int va_offset; > + void *va_slot; > + int ret; > + > + encl_page->desc &= ~SGX_ENCL_PAGE_RECLAIMED; > + > + va_page = list_first_entry(&encl->va_pages, struct sgx_va_page, > + list); > + va_offset = sgx_alloc_va_slot(va_page); > + va_slot = sgx_get_epc_addr(va_page->epc_page) + va_offset; > + if (sgx_va_page_full(va_page)) > + list_move_tail(&va_page->list, &encl->va_pages); > + > + ret = __sgx_encl_ewb(epc_page, va_slot, backing); > + if (ret == SGX_NOT_TRACKED) { > + ret = __etrack(sgx_get_epc_addr(encl->secs.epc_page)); > + if (ret) { > + if (encls_failed(ret)) > + ENCLS_WARN(ret, "ETRACK"); > + } > + > + ret = __sgx_encl_ewb(epc_page, va_slot, backing); > + if (ret == SGX_NOT_TRACKED) { > + /* > + * Slow path, send IPIs to kick cpus out of the > + * enclave. Note, it's imperative that the cpu > + * mask is generated *after* ETRACK, else we'll > + * miss cpus that entered the enclave between > + * generating the mask and incrementing epoch. > + */ > + on_each_cpu_mask(sgx_encl_ewb_cpumask(encl), > + sgx_ipi_cb, NULL, 1); > + ret = __sgx_encl_ewb(epc_page, va_slot, backing); > + } > + } > + > + if (ret) { > + if (encls_failed(ret)) > + ENCLS_WARN(ret, "EWB"); > + > + sgx_free_va_slot(va_page, va_offset); > + } else { > + encl_page->desc |= va_offset; > + encl_page->va_page = va_page; > + } ... > +static void sgx_reclaim_pages(void) > +{ > + struct sgx_epc_page *chunk[SGX_NR_TO_SCAN]; > + struct sgx_backing backing[SGX_NR_TO_SCAN]; > + struct sgx_epc_section *section; > + struct sgx_encl_page *encl_page; > + struct sgx_epc_page *epc_page; > + int cnt = 0; > + int ret; > + int i; > + > + spin_lock(&sgx_active_page_list_lock); > + for (i = 0; i < SGX_NR_TO_SCAN; i++) { > + if (list_empty(&sgx_active_page_list)) Isn't it enough to do this once, i.e., not in the loop? You're holding sgx_active_page_list_lock... > + 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; > + > + if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) > + chunk[cnt++] = epc_page; > + else > + /* The owner is freeing the page. No need to add the > + * page back to the list of reclaimable pages. > + */ > + epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE; > + } > + spin_unlock(&sgx_active_page_list_lock); > + > + for (i = 0; i < cnt; i++) { > + epc_page = chunk[i]; > + encl_page = epc_page->owner; > + > + if (!sgx_reclaimer_age(epc_page)) > + goto skip; > + > + ret = sgx_encl_get_backing(encl_page->encl, > + SGX_ENCL_PAGE_INDEX(encl_page), > + &backing[i]); > + if (ret) > + goto skip; > + > + mutex_lock(&encl_page->encl->lock); > + encl_page->desc |= SGX_ENCL_PAGE_RECLAIMED; > + mutex_unlock(&encl_page->encl->lock); > + continue; > + > +skip: > + spin_lock(&sgx_active_page_list_lock); > + list_add_tail(&epc_page->list, &sgx_active_page_list); > + spin_unlock(&sgx_active_page_list_lock); > + > + kref_put(&encl_page->encl->refcount, sgx_encl_release); > + > + chunk[i] = NULL; > + } > + > + for (i = 0; i < cnt; i++) { > + epc_page = chunk[i]; > + if (epc_page) > + sgx_reclaimer_block(epc_page); > + } > + > + for (i = 0; i < cnt; i++) { > + epc_page = chunk[i]; > + if (!epc_page) > + continue; > + > + encl_page = epc_page->owner; > + sgx_reclaimer_write(epc_page, &backing[i]); > + sgx_encl_put_backing(&backing[i], true); > + > + kref_put(&encl_page->encl->refcount, sgx_encl_release); > + epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE; > + > + section = sgx_get_epc_section(epc_page); > + spin_lock(§ion->lock); > + list_add_tail(&epc_page->list, §ion->page_list); > + section->free_cnt++; > + spin_unlock(§ion->lock); > + } > +} > + > > static void sgx_sanitize_section(struct sgx_epc_section *section) ... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette