From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45174) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WjlPB-00004s-05 for qemu-devel@nongnu.org; Mon, 12 May 2014 04:16:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WjlP1-0002Xz-4l for qemu-devel@nongnu.org; Mon, 12 May 2014 04:16:12 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:47605) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WjlP0-0002Xm-RO for qemu-devel@nongnu.org; Mon, 12 May 2014 04:16:03 -0400 Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 12 May 2014 09:16:02 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 7E869219005C for ; Mon, 12 May 2014 09:15:50 +0100 (BST) Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by b06cxnps3074.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s4C8FxNQ55050252 for ; Mon, 12 May 2014 08:15:59 GMT Received: from d06av03.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s4C8FwYd014060 for ; Mon, 12 May 2014 02:15:58 -0600 Date: Mon, 12 May 2014 10:15:57 +0200 From: Cornelia Huck Message-ID: <20140512101557.0a112367.cornelia.huck@de.ibm.com> In-Reply-To: <20140512093339.5f2e30e1@oc7435384737.ibm.com> References: <1399824664-3499-1-git-send-email-agraf@suse.de> <20140512093339.5f2e30e1@oc7435384737.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] kvm: Fix enable_cap helpers on older gcc List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: Alexander Graf , qemu-devel@nongnu.org On Mon, 12 May 2014 09:33:39 +0200 Thomas Huth wrote: > On Sun, 11 May 2014 18:11:04 +0200 > Alexander Graf wrote: > > > Commit 40f1ee27aa1 introduced handy helpers for enable_cap calls on > > vcpu and vm level. Unfortunately some older gcc versions (4.7.1, 4.6) > > seem to choke on signedness detection in inline created variables: > > > > target-ppc/kvm.c: In function 'kvmppc_booke_watchdog_enable': > > target-ppc/kvm.c:1302:21: error: comparison of unsigned expression < 0 is always false [-Werror=type-limits] > > target-ppc/kvm.c: In function 'kvmppc_set_papr': > > target-ppc/kvm.c:1504:21: error: comparison of unsigned expression < 0 is always false [-Werror=type-limits] > > > > We can easily work around this by not doing a compare with 0, but instead > > shift all values up by one. The resulting binary should look the same, as > > all those ARRAY_SIZE values are compile time statically optimized. > > > > This patch fixes compile errors on some of my systems. > > > > Signed-off-by: Alexander Graf > > --- > > include/sysemu/kvm.h | 12 ++++++------ > > 1 file changed, 6 insertions(+), 6 deletions(-) > > > > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h > > index 192fe89..989c261 100644 > > --- a/include/sysemu/kvm.h > > +++ b/include/sysemu/kvm.h > > @@ -302,9 +302,9 @@ int kvm_check_extension(KVMState *s, unsigned int extension); > > }; \ > > uint64_t args_tmp[] = { __VA_ARGS__ }; \ > > int i; \ > > - for (i = 0; i < ARRAY_SIZE(args_tmp) && \ > > - i < ARRAY_SIZE(cap.args); i++) { \ > > - cap.args[i] = args_tmp[i]; \ > > + for (i = 1; i < (MIN(ARRAY_SIZE(args_tmp), \ > > + ARRAY_SIZE(cap.args)) + 1); i++) { \ > > + cap.args[i - 1] = args_tmp[i - 1]; \ > > } \ > > kvm_vm_ioctl(s, KVM_ENABLE_CAP, &cap); \ > > }) > > @@ -317,9 +317,9 @@ int kvm_check_extension(KVMState *s, unsigned int extension); > > }; \ > > uint64_t args_tmp[] = { __VA_ARGS__ }; \ > > int i; \ > > - for (i = 0; i < ARRAY_SIZE(args_tmp) && \ > > - i < ARRAY_SIZE(cap.args); i++) { \ > > - cap.args[i] = args_tmp[i]; \ > > + for (i = 1; i < (MIN(ARRAY_SIZE(args_tmp), \ > > + ARRAY_SIZE(cap.args)) + 1); i++) { \ > > + cap.args[i - 1] = args_tmp[i - 1]; \ > > } \ > > kvm_vcpu_ioctl(cpu, KVM_ENABLE_CAP, &cap); \ > > }) > > That looks ... somewhat ugly. I think you either should add a proper > comment here (or somebody will fix it back in the future when reading > the code), ... or would it also work to type-cast the result of > ARRAY_SIZE to "int"? Something like this: > > for (i = 0; i < (int)ARRAY_SIZE(args_tmp) && \ > i < (int)ARRAY_SIZE(cap.args); i++) If that one works, I'd prefer that. The other version hurts my eyes :( If it doesn't, I agree it should be properly commented.