From patchwork Tue Mar 1 12:58:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 12764722 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 13D00C433EF for ; Tue, 1 Mar 2022 12:58:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234865AbiCAM6l (ORCPT ); Tue, 1 Mar 2022 07:58:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230415AbiCAM6l (ORCPT ); Tue, 1 Mar 2022 07:58:41 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0629F13DF1; Tue, 1 Mar 2022 04:58:00 -0800 (PST) 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 AF166B818D4; Tue, 1 Mar 2022 12:57:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80B30C340EE; Tue, 1 Mar 2022 12:57:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646139477; bh=r75Uzu8npn39r4huc5vp0QUopdOSRjOWjwUwuLTzzJI=; h=From:To:Cc:Subject:Date:From; b=XIT+/WNf0MDXISpteczFZnD/f5tbZVR5uIq6Fzan3pquU0MfcU2IlMQBIKrq5m3DH s05RAN2ZmV4eeHhA7iRpGps69DTryLghWkCd2obVPwOitVKTfoGzx5brGkwcc4V5ac lIaJdrBkf43/9lTEBqmsHa5gOW0p8Q5M5Yn4bWeeoBSTzxp5ayhA42Ksn4NbsWpy8w 21I+89A7bmhKxJeMPoDrYSlw/iI8KsqwK7sTypVXXgn43DZPQ8k5qFnemRPsArJLVE bLEAPzJUvirns5poA7Ssfq07ww27IK9aGNYzBqkIsUquTCorTUbZTuMCwg4b/+95JG S+ZyQocZGKwRA== From: Jarkko Sakkinen To: linux-sgx@vger.kernel.org Cc: Jarkko Sakkinen , Dave Hansen , stable@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)), "H. Peter Anvin" , Sean Christopherson , Jethro Beekman , linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)) Subject: [PATCH v5] x86/sgx: Free backing memory after faulting the enclave page Date: Tue, 1 Mar 2022 13:58:36 +0100 Message-Id: <20220301125836.3430-1-jarkko@kernel.org> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org There is a limited amount of SGX memory (EPC) on each system. When that memory is used up, SGX has its own swapping mechanism which is similar in concept but totally separate from the core mm/* code. Instead of swapping to disk, SGX swaps from EPC to normal RAM. That normal RAM comes from a shared memory pseudo-file and can itself be swapped by the core mm code. There is a hierarchy like this: EPC <-> shmem <-> disk After data is swapped back in from shmem to EPC, the shmem backing storage needs to be freed. Currently, the backing shmem is not freed. This effectively wastes the shmem while the enclave is running. The memory is recovered when the enclave is destroyed and the backing storage freed. Sort this out by freeing memory with shmem_truncate_range(), as soon as a page is faulted back to the EPC. In addition, free the memory for PCMD pages as soon as all PCMD's in a page have been marked as unused by zeroing its contents. Reported-by: Dave Hansen Cc: stable@vger.kernel.org Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") Signed-off-by: Jarkko Sakkinen --- v5: * Encapsulated file offset calculation for PCMD struct. * Replaced "magic number" PAGE_SIZE with sizeof(struct sgx_secs) to make the offset calculation more self-documentative. v4: * Sanitized the offset calculations. v3: * Resend. v2: * Rewrite commit message as proposed by Dave. * Truncate PCMD pages (Dave). --- arch/x86/kernel/cpu/sgx/encl.c | 57 ++++++++++++++++++++++++++++------ 1 file changed, 48 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 8be6f0592bdc..3d2ed8d27747 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -12,6 +12,30 @@ #include "encls.h" #include "sgx.h" +/* + * Calculate byte offset of a PCMD struct associated with an enclave page. PCMD's + * follow right after the EPC data in the backing storage. In addition to the + * visible enclave pages, there's one extra page slot for SECS, before PCMD + * structs. + */ +static inline pgoff_t sgx_encl_get_backing_page_pcmd_offset(struct sgx_encl *encl, + unsigned long page_index) +{ + pgoff_t epc_end_off = encl->size + sizeof(struct sgx_secs); + + return epc_end_off + page_index * sizeof(struct sgx_pcmd); +} + +/* + * Free a page from the backing storage in the given page index. + */ +static inline void sgx_encl_truncate_backing_page(struct sgx_encl *encl, unsigned long page_index) +{ + struct inode *inode = file_inode(encl->backing); + + shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1); +} + /* * ELDU: Load an EPC page as unblocked. For more info, see "OS Management of EPC * Pages" in the SDM. @@ -22,9 +46,11 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, { unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK; struct sgx_encl *encl = encl_page->encl; + pgoff_t page_index, page_pcmd_off; struct sgx_pageinfo pginfo; struct sgx_backing b; - pgoff_t page_index; + bool pcmd_page_empty; + u8 *pcmd_page; int ret; if (secs_page) @@ -32,14 +58,16 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, else page_index = PFN_DOWN(encl->size); + page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index); + ret = sgx_encl_lookup_backing(encl, page_index, &b); if (ret) return ret; pginfo.addr = encl_page->desc & PAGE_MASK; pginfo.contents = (unsigned long)kmap_atomic(b.contents); - pginfo.metadata = (unsigned long)kmap_atomic(b.pcmd) + - b.pcmd_offset; + pcmd_page = kmap_atomic(b.pcmd); + pginfo.metadata = (unsigned long)pcmd_page + b.pcmd_offset; if (secs_page) pginfo.secs = (u64)sgx_get_epc_virt_addr(secs_page); @@ -55,11 +83,24 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, ret = -EFAULT; } - kunmap_atomic((void *)(unsigned long)(pginfo.metadata - b.pcmd_offset)); + memset(pcmd_page + b.pcmd_offset, 0, sizeof(struct sgx_pcmd)); + + /* + * The area for the PCMD in the page was zeroed above. Check if the + * whole page is now empty meaning that all PCMD's have been zeroed: + */ + pcmd_page_empty = !memchr_inv(pcmd_page, 0, PAGE_SIZE); + + kunmap_atomic(pcmd_page); kunmap_atomic((void *)(unsigned long)pginfo.contents); sgx_encl_put_backing(&b, false); + sgx_encl_truncate_backing_page(encl, page_index); + + if (pcmd_page_empty) + sgx_encl_truncate_backing_page(encl, PFN_DOWN(page_pcmd_off)); + return ret; } @@ -583,7 +624,7 @@ static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl, 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); + pgoff_t page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index); struct page *contents; struct page *pcmd; @@ -591,7 +632,7 @@ static int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, if (IS_ERR(contents)) return PTR_ERR(contents); - pcmd = sgx_encl_get_backing_page(encl, pcmd_index); + pcmd = sgx_encl_get_backing_page(encl, PFN_DOWN(page_pcmd_off)); if (IS_ERR(pcmd)) { put_page(contents); return PTR_ERR(pcmd); @@ -600,9 +641,7 @@ static int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index, backing->page_index = page_index; backing->contents = contents; backing->pcmd = pcmd; - backing->pcmd_offset = - (page_index & (PAGE_SIZE / sizeof(struct sgx_pcmd) - 1)) * - sizeof(struct sgx_pcmd); + backing->pcmd_offset = page_pcmd_off & (PAGE_SIZE - 1); return 0; }