From: Ian Campbell <Ian.Campbell@citrix.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"arnd@arndb.de" <arnd@arndb.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"linaro-dev@lists.linaro.org" <linaro-dev@lists.linaro.org>,
David Vrabel <david.vrabel@citrix.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH-WIP 01/13] xen/arm: use r12 to pass the hypercall number to the hypervisor
Date: Mon, 27 Feb 2012 16:27:23 +0000 [thread overview]
Message-ID: <1330360043.8557.302.camel@zakaz.uk.xensource.com> (raw)
In-Reply-To: <1330019314-20865-1-git-send-email-stefano.stabellini@eu.citrix.com>
On Thu, 2012-02-23 at 17:48 +0000, Stefano Stabellini wrote:
> 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".
R12 is not accessible from the 16 bit "T1" Thumb encoding of mov
immediate (which can only target r0..r7).
Since we support only ARMv7+ there are "T2" and "T3" encodings available
which do allow direct mov of an immediate into R12, but are 32 bit Thumb
instructions.
Should we use r7 instead to maximise instruction density for Thumb code?
Ian.
next prev parent reply other threads:[~2012-02-27 16:27 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-23 17:47 [PATCH-WIP 00/13] xen/arm: receive Xen events and initialize xenbus Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 01/13] xen/arm: use r12 to pass the hypercall number to the hypervisor Stefano Stabellini
2012-02-27 16:27 ` Ian Campbell [this message]
2012-02-27 18:03 ` Dave Martin
2012-02-27 19:33 ` Ian Campbell
2012-02-28 10:20 ` Dave Martin
2012-02-28 10:48 ` Ian Campbell
2012-02-28 12:28 ` Stefano Stabellini
2012-02-29 9:34 ` Dave Martin
2012-02-29 9:56 ` Ian Campbell
2012-02-29 11:47 ` Dave Martin
2012-02-29 12:58 ` Dave Martin
2012-02-29 14:44 ` Ian Campbell
2012-03-01 9:35 ` Dave Martin
2012-03-01 10:12 ` Russell King - ARM Linux
2012-03-02 21:19 ` Nicolas Pitre
2012-02-29 14:52 ` Stefano Stabellini
2012-03-01 9:51 ` Dave Martin
2012-03-01 10:10 ` Russell King - ARM Linux
2012-03-01 10:27 ` Dave Martin
2012-03-01 10:35 ` Russell King - ARM Linux
2012-03-01 12:12 ` Stefano Stabellini
2012-03-02 21:15 ` Nicolas Pitre
2012-03-08 9:58 ` Richard Earnshaw
2012-03-08 12:17 ` Dave Martin
2012-03-08 17:21 ` Nicolas Pitre
2012-03-08 18:47 ` Richard Earnshaw
2012-03-09 15:58 ` Dave Martin
2012-03-09 16:20 ` Nicolas Pitre
2012-03-09 17:38 ` Richard Earnshaw
2012-02-27 21:05 ` Peter Maydell
2012-02-28 10:12 ` Ian Campbell
2012-02-27 17:53 ` Dave Martin
2012-02-27 19:48 ` Ian Campbell
2012-02-28 9:46 ` Dave Martin
2012-02-28 10:07 ` Ian Campbell
2012-02-28 12:21 ` Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 02/13] xen/arm: introduce privcmp, physdev_op and memory_op hypercalls Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 03/13] xen/arm: mmu.h and page.h related definitions Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 04/13] xen/arm: sync_bitops Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 05/13] xen/arm: empty implementation of grant_table arch specific functions Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 06/13] xen/arm: missing includes Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 07/13] xen/arm: receive xen events on arm Stefano Stabellini
2012-02-24 11:12 ` David Vrabel
2012-02-24 12:23 ` Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 08/13] xen/arm: fix arm xen guest handle definitions Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 09/13] xen/arm: shared_info and start_info Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 10/13] xen/arm: empty implementation of xen_remap_domain_mfn_range Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 11/13] xen/arm: Introduce xen_pfn_t for pfn and mfn types Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 12/13] xen/arm: compile and run xenbus Stefano Stabellini
2012-02-23 17:48 ` [PATCH-WIP 13/13] xen/arm: compile grant-table features events and xenbus, do not compile pci Stefano Stabellini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1330360043.8557.302.camel@zakaz.uk.xensource.com \
--to=ian.campbell@citrix.com \
--cc=arnd@arndb.de \
--cc=catalin.marinas@arm.com \
--cc=david.vrabel@citrix.com \
--cc=kvm@vger.kernel.org \
--cc=linaro-dev@lists.linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=stefano.stabellini@eu.citrix.com \
--cc=xen-devel@lists.xensource.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®