From patchwork Mon Aug 12 17:29:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 11090299 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B06831399 for ; Mon, 12 Aug 2019 17:32:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A2DB4283A5 for ; Mon, 12 Aug 2019 17:32:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 97460284DB; Mon, 12 Aug 2019 17:32:04 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 242FA283A5 for ; Mon, 12 Aug 2019 17:32:04 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hxE9V-0006hX-B4; Mon, 12 Aug 2019 17:30:37 +0000 Received: from [172.99.69.81] (helo=us1-rack-iad1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hxE9T-0006hC-Lo for xen-devel@lists.xenproject.org; Mon, 12 Aug 2019 17:30:35 +0000 X-Inumbo-ID: e206497c-bd26-11e9-9c85-8b766f5a9059 Received: from foss.arm.com (unknown [217.140.110.172]) by us1-rack-iad1.inumbo.com (Halon) with ESMTP id e206497c-bd26-11e9-9c85-8b766f5a9059; Mon, 12 Aug 2019 17:30:31 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D5A8315AB; Mon, 12 Aug 2019 10:30:30 -0700 (PDT) Received: from e108454-lin.cambridge.arm.com (e108454-lin.cambridge.arm.com [10.1.196.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2FF9A3F706; Mon, 12 Aug 2019 10:30:30 -0700 (PDT) From: Julien Grall To: xen-devel@lists.xenproject.org Date: Mon, 12 Aug 2019 18:29:55 +0100 Message-Id: <20190812173019.11956-5-julien.grall@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20190812173019.11956-1-julien.grall@arm.com> References: <20190812173019.11956-1-julien.grall@arm.com> Subject: [Xen-devel] [PATCH v3 04/28] xen/arm64: head: Rework and document launch() X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Julien Grall , Stefano Stabellini , Volodymyr Babchuk MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP Boot CPU and secondary CPUs will use different entry point to C code. At the moment, the decision on which entry to use is taken within launch(). In order to avoid a branch for the decision and make the code clearer, launch() is reworked to take in parameters the entry point and its arguments. Lastly, document the behavior and the main registers usage within the function. Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini --- Changes in v3: - Indent all the comments the same way - Add Stefano's reviewed-by Changes in v2: - Use x3 instead of x4 - Add a clobbers section --- xen/arch/arm/arm64/head.S | 43 +++++++++++++++++++++++++++---------------- 1 file changed, 27 insertions(+), 16 deletions(-) diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index 7b6b820726..925fb93e58 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -318,6 +318,11 @@ primary_switched: /* Use a virtual address to access the UART. */ ldr x23, =EARLY_UART_VIRTUAL_ADDRESS #endif + PRINT("- Ready -\r\n") + /* Setup the arguments for start_xen and jump to C world */ + mov x0, x20 /* x0 := Physical offset */ + mov x1, x21 /* x1 := paddr(FDT) */ + ldr x2, =start_xen b launch ENDPROC(real_start) @@ -380,6 +385,9 @@ secondary_switched: /* Use a virtual address to access the UART. */ ldr x23, =EARLY_UART_VIRTUAL_ADDRESS #endif + PRINT("- Ready -\r\n") + /* Jump to C world */ + ldr x2, =start_secondary b launch ENDPROC(init_secondary) @@ -741,23 +749,26 @@ setup_fixmap: ret ENDPROC(setup_fixmap) +/* + * Setup the initial stack and jump to the C world + * + * Inputs: + * x0 : Argument 0 of the C function to call + * x1 : Argument 1 of the C function to call + * x2 : C entry point + * + * Clobbers x3 + */ launch: - PRINT("- Ready -\r\n") - - ldr x0, =init_data - add x0, x0, #INITINFO_stack /* Find the boot-time stack */ - ldr x0, [x0] - add x0, x0, #STACK_SIZE /* (which grows down from the top). */ - sub x0, x0, #CPUINFO_sizeof /* Make room for CPU save record */ - mov sp, x0 - - cbnz x22, 1f - - mov x0, x20 /* Marshal args: - phys_offset */ - mov x1, x21 /* - FDT */ - b start_xen /* and disappear into the land of C */ -1: - b start_secondary /* (to the appropriate entry point) */ + ldr x3, =init_data + add x3, x3, #INITINFO_stack /* Find the boot-time stack */ + ldr x3, [x3] + add x3, x3, #STACK_SIZE /* (which grows down from the top). */ + sub x3, x3, #CPUINFO_sizeof /* Make room for CPU save record */ + mov sp, x3 + + /* Jump to C world */ + br x2 ENDPROC(launch) /* Fail-stop */