From patchwork Fri Oct 9 19:49:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ira Weiny X-Patchwork-Id: 287185 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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 B0A13C43467 for ; Fri, 9 Oct 2020 20:10:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 666D920659 for ; Fri, 9 Oct 2020 20:10:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391944AbgJIUKq (ORCPT ); Fri, 9 Oct 2020 16:10:46 -0400 Received: from mga17.intel.com ([192.55.52.151]:33872 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403820AbgJITvD (ORCPT ); Fri, 9 Oct 2020 15:51:03 -0400 IronPort-SDR: eqJBBpkrLGrKis4SJXQed/VSxmErjrdjeWymzKs05Z9O/Kb0aN689/V3XKJa5P7vgO3L6+mg6b 0K1uqxQQciVg== X-IronPort-AV: E=McAfee;i="6000,8403,9769"; a="145397219" X-IronPort-AV: E=Sophos;i="5.77,355,1596524400"; d="scan'208";a="145397219" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 12:50:59 -0700 IronPort-SDR: /j9oTf64Lc/fwCVe0LT3Z3/pz5zJXnOJNQAbfqyJqoBSoEhIO3zt/eOhOuH8Xl1K1eBwx2q0zq 2edyiKrU43UQ== X-IronPort-AV: E=Sophos;i="5.77,355,1596524400"; d="scan'208";a="519846797" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 12:50:59 -0700 From: ira.weiny@intel.com To: Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra Cc: Ira Weiny , Randy Dunlap , x86@kernel.org, Dave Hansen , Dan Williams , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kexec@lists.infradead.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, devel@driverdev.osuosl.org, linux-efi@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-um@lists.infradead.org, linux-ntfs-dev@lists.sourceforge.net, reiserfs-devel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nilfs@vger.kernel.org, cluster-devel@redhat.com, ecryptfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-afs@lists.infradead.org, linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, xen-devel@lists.xenproject.org, linux-cachefs@redhat.com, samba-technical@lists.samba.org, intel-wired-lan@lists.osuosl.org Subject: [PATCH RFC PKS/PMEM 04/58] kmap: Add stray access protection for device pages Date: Fri, 9 Oct 2020 12:49:39 -0700 Message-Id: <20201009195033.3208459-5-ira.weiny@intel.com> X-Mailer: git-send-email 2.28.0.rc0.12.gb6a658bd00c9 In-Reply-To: <20201009195033.3208459-1-ira.weiny@intel.com> References: <20201009195033.3208459-1-ira.weiny@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org From: Ira Weiny Device managed pages may have additional protections. These protections need to be removed prior to valid use by kernel users. Check for special treatment of device managed pages in kmap and take action if needed. We use kmap as an interface for generic kernel code because under normal circumstances it would be a bug for general kernel code to not use kmap prior to accessing kernel memory. Therefore, this should allow any valid kernel users to seamlessly use these pages without issues. Because of the critical nature of kmap it must be pointed out that the over head on regular DRAM is carefully implemented to be as fast as possible. Furthermore the underlying MSR write required on device pages when protected is better than a normal MSR write. Specifically, WRMSR(MSR_IA32_PKRS) is not serializing but still maintains ordering properties similar to WRPKRU. The current SDM section on PKRS needs updating but should be the same as that of WRPKRU. So to quote from the WRPKRU text: WRPKRU will never execute speculatively. Memory accesses affected by PKRU register will not execute (even speculatively) until all prior executions of WRPKRU have completed execution and updated the PKRU register. Still this will make accessing pmem more expensive from the kernel but the overhead is minimized and many pmem users access this memory through user page mappings which are not affected at all. Cc: Randy Dunlap Signed-off-by: Ira Weiny --- include/linux/highmem.h | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 14e6202ce47f..2a9806e3b8d2 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -8,6 +8,7 @@ #include #include #include +#include #include @@ -31,6 +32,20 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size) #include +static inline void dev_page_enable_access(struct page *page, bool global) +{ + if (!page_is_access_protected(page)) + return; + dev_access_enable(global); +} + +static inline void dev_page_disable_access(struct page *page, bool global) +{ + if (!page_is_access_protected(page)) + return; + dev_access_disable(global); +} + #ifdef CONFIG_HIGHMEM extern void *kmap_atomic_high_prot(struct page *page, pgprot_t prot); extern void kunmap_atomic_high(void *kvaddr); @@ -55,6 +70,11 @@ static inline void *kmap(struct page *page) else addr = kmap_high(page); kmap_flush_tlb((unsigned long)addr); + /* + * Even non-highmem pages may have additional access protections which + * need to be checked and potentially enabled. + */ + dev_page_enable_access(page, true); return addr; } @@ -63,6 +83,11 @@ void kunmap_high(struct page *page); static inline void kunmap(struct page *page) { might_sleep(); + /* + * Even non-highmem pages may have additional access protections which + * need to be checked and potentially disabled. + */ + dev_page_disable_access(page, true); if (!PageHighMem(page)) return; kunmap_high(page); @@ -85,6 +110,7 @@ static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) { preempt_disable(); pagefault_disable(); + dev_page_enable_access(page, false); if (!PageHighMem(page)) return page_address(page); return kmap_atomic_high_prot(page, prot); @@ -137,6 +163,7 @@ static inline unsigned long totalhigh_pages(void) { return 0UL; } static inline void *kmap(struct page *page) { might_sleep(); + dev_page_enable_access(page, true); return page_address(page); } @@ -146,6 +173,7 @@ static inline void kunmap_high(struct page *page) static inline void kunmap(struct page *page) { + dev_page_disable_access(page, true); #ifdef ARCH_HAS_FLUSH_ON_KUNMAP kunmap_flush_on_unmap(page_address(page)); #endif @@ -155,6 +183,7 @@ static inline void *kmap_atomic(struct page *page) { preempt_disable(); pagefault_disable(); + dev_page_enable_access(page, false); return page_address(page); } #define kmap_atomic_prot(page, prot) kmap_atomic(page) @@ -216,7 +245,8 @@ static inline void kmap_atomic_idx_pop(void) #define kunmap_atomic(addr) \ do { \ BUILD_BUG_ON(__same_type((addr), struct page *)); \ - kunmap_atomic_high(addr); \ + dev_page_disable_access(kmap_to_page(addr), false); \ + kunmap_atomic_high(addr); \ pagefault_enable(); \ preempt_enable(); \ } while (0)