Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758090Ab2HHMlS (ORCPT ); Wed, 8 Aug 2012 08:41:18 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:61926 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757995Ab2HHMlR (ORCPT ); Wed, 8 Aug 2012 08:41:17 -0400 Date: Wed, 8 Aug 2012 13:41:11 +0100 From: Dave Martin To: Stefano Stabellini Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, linaro-dev@lists.linaro.org, Ian.Campbell@citrix.com, arnd@arndb.de, konrad.wilk@oracle.com, catalin.marinas@arm.com, tim@xen.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 02/23] xen/arm: hypercalls Message-ID: <20120808124111.GB2134@linaro.org> References: <1344263246-28036-2-git-send-email-stefano.stabellini@eu.citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1344263246-28036-2-git-send-email-stefano.stabellini@eu.citrix.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5807 Lines: 168 On Mon, Aug 06, 2012 at 03:27:05PM +0100, Stefano Stabellini wrote: > Use r12 to pass the hypercall number to the hypervisor. > > We need a register to pass the hypercall number because we might not > know it at compile time and HVC only takes an immediate argument. > > Among the available registers r12 seems to be the best choice because it > is defined as "intra-procedure call scratch register". > > Use the ISS to pass an hypervisor specific tag. > > Changes in v2: > - define an HYPERCALL macro for 5 arguments hypercall wrappers, even if > at the moment is unused; > - use ldm instead of pop; > - fix up comments. > > Signed-off-by: Stefano Stabellini > --- > arch/arm/include/asm/xen/hypercall.h | 50 ++++++++++++++++ > arch/arm/xen/Makefile | 2 +- > arch/arm/xen/hypercall.S | 106 ++++++++++++++++++++++++++++++++++ > 3 files changed, 157 insertions(+), 1 deletions(-) > create mode 100644 arch/arm/include/asm/xen/hypercall.h > create mode 100644 arch/arm/xen/hypercall.S [...] > diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S > new file mode 100644 > index 0000000..074f5ed > --- /dev/null > +++ b/arch/arm/xen/hypercall.S > @@ -0,0 +1,106 @@ > +/****************************************************************************** > + * hypercall.S > + * > + * Xen hypercall wrappers > + * > + * Stefano Stabellini , Citrix, 2012 > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License version 2 > + * as published by the Free Software Foundation; or, when distributed > + * separately from the Linux kernel or incorporated into other > + * software packages, subject to the following license: > + * > + * Permission is hereby granted, free of charge, to any person obtaining a copy > + * of this source file (the "Software"), to deal in the Software without > + * restriction, including without limitation the rights to use, copy, modify, > + * merge, publish, distribute, sublicense, and/or sell copies of the Software, > + * and to permit persons to whom the Software is furnished to do so, subject to > + * the following conditions: > + * > + * The above copyright notice and this permission notice shall be included in > + * all copies or substantial portions of the Software. > + * > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE > + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS > + * IN THE SOFTWARE. > + */ > + > +/* > + * The Xen hypercall calling convention is very similar to the ARM > + * procedure calling convention: the first paramter is passed in r0, the > + * second in r1, the third in r2 and the fourth in r3. Considering that > + * Xen hypercalls have 5 arguments at most, the fifth paramter is passed > + * in r4, differently from the procedure calling convention of using the > + * stack for that case. > + * > + * The hypercall number is passed in r12. > + * > + * The return value is in r0. > + * > + * The hvc ISS is required to be 0xEA1, that is the Xen specific ARM > + * hypercall tag. > + */ > + > +#include > +#include > +#include > + > + > +/* HVC 0xEA1 */ > +#ifdef CONFIG_THUMB2_KERNEL > +#define xen_hvc .word 0xf7e08ea1 > +#else > +#define xen_hvc .word 0xe140ea71 > +#endif Consider using my opcode injection helpers patch for this (see separate repost: [PATCH v2 REPOST 0/4] ARM: opcodes: Facilitate custom opcode injection), assuming that nobody objects to it. This should mean that the right opcodes get generated when building a kernel for a big- endian target for example. I believe the __HVC(imm) macro which I put in as an example should do what you need in this case. > + > +#define HYPERCALL_SIMPLE(hypercall) \ > +ENTRY(HYPERVISOR_##hypercall) \ > + mov r12, #__HYPERVISOR_##hypercall; \ > + xen_hvc; \ > + mov pc, lr; \ > +ENDPROC(HYPERVISOR_##hypercall) > + > +#define HYPERCALL0 HYPERCALL_SIMPLE > +#define HYPERCALL1 HYPERCALL_SIMPLE > +#define HYPERCALL2 HYPERCALL_SIMPLE > +#define HYPERCALL3 HYPERCALL_SIMPLE > +#define HYPERCALL4 HYPERCALL_SIMPLE > + > +#define HYPERCALL5(hypercall) \ > +ENTRY(HYPERVISOR_##hypercall) \ > + stmdb sp!, {r4} \ > + ldr r4, [sp, #4] \ > + mov r12, #__HYPERVISOR_##hypercall; \ > + xen_hvc \ > + ldm sp!, {r4} \ > + mov pc, lr \ > +ENDPROC(HYPERVISOR_##hypercall) > + > + .text > + > +HYPERCALL2(xen_version); > +HYPERCALL3(console_io); > +HYPERCALL3(grant_table_op); > +HYPERCALL2(sched_op); > +HYPERCALL2(event_channel_op); > +HYPERCALL2(hvm_op); > +HYPERCALL2(memory_op); > +HYPERCALL2(physdev_op); > + > +ENTRY(privcmd_call) > + stmdb sp!, {r4} > + mov r12, r0 > + mov r0, r1 > + mov r1, r2 > + mov r2, r3 > + ldr r3, [sp, #8] > + ldr r4, [sp, #4] > + xen_hvc > + ldm sp!, {r4} > + mov pc, lr Note that the preferred entry/exit sequences in such cases are: stmfd sp!, {r4,lr} ... ldmfd sp!, {r4,pc} ...but it works either way. I would bother to change it unless you have other changes to make too. Cheers ---Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/