From patchwork Thu Mar 2 14:59:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 13157400 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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0FA19C7EE36 for ; Thu, 2 Mar 2023 14:59:33 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.505000.777530 (Exim 4.92) (envelope-from ) id 1pXkP1-0001k9-Ir; Thu, 02 Mar 2023 14:59:27 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 505000.777530; Thu, 02 Mar 2023 14:59:27 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pXkP1-0001it-Bf; Thu, 02 Mar 2023 14:59:27 +0000 Received: by outflank-mailman (input) for mailman id 505000; Thu, 02 Mar 2023 14:59:26 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pXkP0-0001Eg-68 for xen-devel@lists.xenproject.org; Thu, 02 Mar 2023 14:59:26 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pXkP0-0003h4-1c; Thu, 02 Mar 2023 14:59:26 +0000 Received: from 54-240-197-232.amazon.com ([54.240.197.232] helo=dev-dsk-jgrall-1b-035652ec.eu-west-1.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1pXkOz-0003fg-QV; Thu, 02 Mar 2023 14:59:26 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:MIME-Version:References: In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=BmjURXf84YUJiKB9eOEY0h/Bknfj426Ddbz4nR7ogr0=; b=woauhNkEfOdiggkhgovC1HVXNG cnNhXaFKcfichNxjReIXa/wHDRfstxok/T68Zfbg0yRKjCW4w7WD9n7HYFGswuwF/icsrXuJqa/jZ wLWk80bh6X6ZaObqtzNx7Zz6fxiGRECU2irGzbeVsrfn2D+LLmDbrF6QGWDOwZ3OvsFA=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: Luca.Fancellu@arm.com, michal.orzel@amd.com, Julien Grall , Luca Fancellu , Bertrand Marquis Subject: [PATCH v6 4/5] xen/arm64: mm: Rework switch_ttbr() Date: Thu, 2 Mar 2023 14:59:15 +0000 Message-Id: <20230302145916.44035-5-julien@xen.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230302145916.44035-1-julien@xen.org> References: <20230302145916.44035-1-julien@xen.org> MIME-Version: 1.0 From: Julien Grall At the moment, switch_ttbr() is switching the TTBR whilst the MMU is still on. Switching TTBR is like replacing existing mappings with new ones. So we need to follow the break-before-make sequence. In this case, it means the MMU needs to be switched off while the TTBR is updated. In order to disable the MMU, we need to first jump to an identity mapping. Rename switch_ttbr() to switch_ttbr_id() and create an helper on top to temporary map the identity mapping and call switch_ttbr() via the identity address. switch_ttbr_id() is now reworked to temporarily turn off the MMU before updating the TTBR. We also need to make sure the helper switch_ttbr() is part of the identity mapping. So move _end_boot past it. The arm32 code will use a different approach. So this issue is for now only resolved on arm64. Signed-off-by: Julien Grall Reviewed-by: Luca Fancellu Tested-by: Luca Fancellu Reviewed-by: Michal Orzel Reviewed-by: Bertrand Marquis ---- Changes in v6: - Add Michal's reviewed-by tag - Add Bertrand's reviewed-by tag Changes in v5: - Add a newline in switch_ttbr() - Add Luca's reviewed-by and tested-by Changes in v4: - Don't modify setup_pagetables() as we don't handle arm32. - Move the clearing of the boot page tables in an earlier patch - Fix the numbering Changes in v2: - Remove the arm32 changes. This will be addressed differently - Re-instate the instruct cache flush. This is not strictly necessary but kept it for safety. - Use "dsb ish" rather than "dsb sy". TODO: * Handle the case where the runtime Xen is loaded at a different position for cache coloring. This will be dealt separately. --- xen/arch/arm/arm64/head.S | 50 +++++++++++++++++++++++------------ xen/arch/arm/arm64/mm.c | 31 ++++++++++++++++++++++ xen/arch/arm/include/asm/mm.h | 2 ++ xen/arch/arm/mm.c | 2 -- 4 files changed, 66 insertions(+), 19 deletions(-) diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index 663f5813b12e..5efd442b24af 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -816,30 +816,46 @@ ENDPROC(fail) * Switch TTBR * * x0 ttbr - * - * TODO: This code does not comply with break-before-make. */ -ENTRY(switch_ttbr) - dsb sy /* Ensure the flushes happen before - * continuing */ - isb /* Ensure synchronization with previous - * changes to text */ - tlbi alle2 /* Flush hypervisor TLB */ - ic iallu /* Flush I-cache */ - dsb sy /* Ensure completion of TLB flush */ +ENTRY(switch_ttbr_id) + /* 1) Ensure any previous read/write have completed */ + dsb ish + isb + + /* 2) Turn off MMU */ + mrs x1, SCTLR_EL2 + bic x1, x1, #SCTLR_Axx_ELx_M + msr SCTLR_EL2, x1 + isb + + /* + * 3) Flush the TLBs. + * See asm/arm64/flushtlb.h for the explanation of the sequence. + */ + dsb nshst + tlbi alle2 + dsb nsh + isb + + /* 4) Update the TTBR */ + msr TTBR0_EL2, x0 isb - msr TTBR0_EL2, x0 + /* + * 5) Flush I-cache + * This should not be necessary but it is kept for safety. + */ + ic iallu + isb - isb /* Ensure synchronization with previous - * changes to text */ - tlbi alle2 /* Flush hypervisor TLB */ - ic iallu /* Flush I-cache */ - dsb sy /* Ensure completion of TLB flush */ + /* 6) Turn on the MMU */ + mrs x1, SCTLR_EL2 + orr x1, x1, #SCTLR_Axx_ELx_M /* Enable MMU */ + msr SCTLR_EL2, x1 isb ret -ENDPROC(switch_ttbr) +ENDPROC(switch_ttbr_id) #ifdef CONFIG_EARLY_PRINTK /* diff --git a/xen/arch/arm/arm64/mm.c b/xen/arch/arm/arm64/mm.c index 56b9e9b8d3ef..78b7c7eb004f 100644 --- a/xen/arch/arm/arm64/mm.c +++ b/xen/arch/arm/arm64/mm.c @@ -120,6 +120,37 @@ void update_identity_mapping(bool enable) BUG_ON(rc); } +extern void switch_ttbr_id(uint64_t ttbr); + +typedef void (switch_ttbr_fn)(uint64_t ttbr); + +void __init switch_ttbr(uint64_t ttbr) +{ + vaddr_t id_addr = virt_to_maddr(switch_ttbr_id); + switch_ttbr_fn *fn = (switch_ttbr_fn *)id_addr; + lpae_t pte; + + /* Enable the identity mapping in the boot page tables */ + update_identity_mapping(true); + + /* Enable the identity mapping in the runtime page tables */ + pte = pte_of_xenaddr((vaddr_t)switch_ttbr_id); + pte.pt.table = 1; + pte.pt.xn = 0; + pte.pt.ro = 1; + write_pte(&xen_third_id[third_table_offset(id_addr)], pte); + + /* Switch TTBR */ + fn(ttbr); + + /* + * Disable the identity mapping in the runtime page tables. + * Note it is not necessary to disable it in the boot page tables + * because they are not going to be used by this CPU anymore. + */ + update_identity_mapping(false); +} + /* * Local variables: * mode: C diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h index 23dec574eb31..4262165ce25e 100644 --- a/xen/arch/arm/include/asm/mm.h +++ b/xen/arch/arm/include/asm/mm.h @@ -207,6 +207,8 @@ extern unsigned long total_pages; extern void setup_pagetables(unsigned long boot_phys_offset); /* Map FDT in boot pagetable */ extern void *early_fdt_map(paddr_t fdt_paddr); +/* Switch to a new root page-tables */ +extern void switch_ttbr(uint64_t ttbr); /* Remove early mappings */ extern void remove_early_mappings(void); /* Allocate and initialise pagetables for a secondary CPU. Sets init_ttbr to the diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 265bc082567e..d4d376f70f50 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -476,8 +476,6 @@ static void xen_pt_enforce_wnx(void) flush_xen_tlb_local(); } -extern void switch_ttbr(uint64_t ttbr); - /* Clear a translation table and clean & invalidate the cache */ static void clear_table(void *table) {