From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH 05/19] xen: arm: Add and use r/o+raz and w/o+wi helpers Date: Fri, 17 Apr 2015 07:18:36 +0100 Message-ID: <5530A5BC.1030202@gmail.com> References: <1427796446.2115.34.camel@citrix.com> <1427796462-24376-5-git-send-email-ian.campbell@citrix.com> <551E8CD5.3080407@citrix.com> <1429201350.25195.175.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1429201350.25195.175.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell , Julien Grall Cc: xen-devel@lists.xen.org, julien.grall@linaro.org, tim@xen.org, stefano.stabellini@eu.citrix.com List-Id: xen-devel@lists.xenproject.org Hi Ian, On 16/04/2015 17:22, Ian Campbell wrote: > On Fri, 2015-04-03 at 14:51 +0200, Julien Grall wrote: >> On 31/03/2015 12:07, Ian Campbell wrote: >>> Signed-off-by: Ian Campbell >>> --- >>> xen/arch/arm/traps.c | 52 ++++++++++++++++++++++++++++++++------------------ >>> 1 file changed, 33 insertions(+), 19 deletions(-) >>> >>> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c >>> index 8b1846a..ebc09f9 100644 >>> --- a/xen/arch/arm/traps.c >>> +++ b/xen/arch/arm/traps.c >>> @@ -1587,6 +1587,34 @@ static void handle_raz_wi(struct cpu_user_regs *regs, >>> advance_pc(regs, hsr); >>> } >>> >>> +/* Write only + write ignore */ >>> +static void handle_wo_wi(struct cpu_user_regs *regs, >>> + register_t *reg, >> >> This helper handles WO and WI which doesn't require to modify the register. >> >> I would pass a register_t rather than register_t* in order to make clear >> that the register of the guest won't change. > > I deliberately made handle_* all have the same prototype for > consistency. Ok. >>> +/* Read only + read as zero */ >> >> This comment may confuse developer who wants to implement RO register >> which another value than 0. >> >> I got confuse too. It would be nice to expand the comment for the RO case. > > I'm afraid I don't understand the confusion so I'm not sure how to > clarify. What did you think this comment was saying? When I read the comment I though you were implemented two distinct part: RO and RAZ. As the value return by RO may not always be 0 (we have a handful of cases in traps.c), I didn't understand why you were implementing both within the same helper. Although this helper choose to implement RO as RAZ. So I think it would be good to mention it in order to avoid confusion later. Regards, -- Julien Grall