From: John Garry <john.garry@huawei.com>
To: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Cc: Joerg Roedel <joro@8bytes.org>, kernel test robot <lkp@intel.com>,
<will@kernel.org>, "robin.murphy@arm.com" <robin.murphy@arm.com>,
"kbuild-all@lists.01.org" <kbuild-all@lists.01.org>,
"trivial@kernel.org" <trivial@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linuxarm <linuxarm@huawei.com>, "maz@kernel.org" <maz@kernel.org>
Subject: Re: [PATCH 4/4] iommu/arm-smmu-v3: Remove cmpxchg() in arm_smmu_cmdq_issue_cmdlist()
Date: Fri, 26 Jun 2020 11:05:13 +0100 [thread overview]
Message-ID: <4f87e2e4-ec7d-49d1-037c-158e94f25ab6@huawei.com> (raw)
In-Reply-To: <CADRDgG5pOstGK=fm8s3Be_v8+vc-EyRYmpiMsTCeK-rMk2ZRQQ@mail.gmail.com>
On 23/06/2020 14:55, Rikard Falkeborn wrote:
> Den tis 23 juni 2020 12:21John Garry <john.garry@huawei.com
> <mailto:john.garry@huawei.com>> skrev:
>
> On 23/06/2020 10:35, Rikard Falkeborn wrote:
> >
> > I'd say that GENMASK_INPUT_CHECK() should be able to handle a
> l=0 and
> > h=unsigned value, so I doubt this warn.
> >
> > Using GENMASK((int)cmdq->q.llq.max_n_shift, 0) resolves it,
> but it
> > looks
> > like GENMASK_INPUT_CHECK() could be improved.
> >
> >
> > Indeed it could, it is fixed in -next.
>
> ok, thanks for the pointer, but I still see this on today's -next with
> this patch:
>
> make W=1 drivers/iommu/arm-smmu-v3.o
>
>
> Oh, ok thanks for reporting. I guess different gcc versions have
> different behaviour. I guess we'll have to change the comparison to
> (!((h) == (l) || (h) > (l))) instead (not sure I got all parenthesis and
> logic correct but you get the idea).
>
Yeah, so this looks to fix it:
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -23,7 +23,8 @@
#include <linux/build_bug.h>
#define GENMASK_INPUT_CHECK(h, l) \
(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
- __builtin_constant_p((l) > (h)), (l) > (h), 0)))
+ __builtin_constant_p(!((h) == (l) ||(h) > (l))), !((h)
== (l) ||(h) > (l)), 0)))
+
We may be able to just use (h) == (l) as the const expr to make it more
concise, but that may be confusing.
I only tested with my toolchain based on 7.5.0
Thanks,
John
next prev parent reply other threads:[~2020-06-26 10:06 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 17:28 [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency John Garry
2020-06-22 17:28 ` [PATCH 1/4] iommu/arm-smmu-v3: Fix trivial typo John Garry
2020-06-22 17:28 ` [PATCH 2/4] iommu/arm-smmu-v3: Calculate bits for prod and owner John Garry
2020-06-22 17:28 ` [PATCH 3/4] iommu/arm-smmu-v3: Always issue a CMD_SYNC per batch John Garry
2020-06-22 17:28 ` [PATCH 4/4] iommu/arm-smmu-v3: Remove cmpxchg() in arm_smmu_cmdq_issue_cmdlist() John Garry
2020-06-23 1:07 ` kernel test robot
2020-06-23 9:21 ` John Garry
[not found] ` <CADRDgG4=uD3Ni6r7D3kHdSo=ketaXKGririHfFvPYq4qz8KjfQ@mail.gmail.com>
2020-06-23 10:19 ` John Garry
[not found] ` <CADRDgG5pOstGK=fm8s3Be_v8+vc-EyRYmpiMsTCeK-rMk2ZRQQ@mail.gmail.com>
2020-06-26 10:05 ` John Garry [this message]
2020-06-23 16:22 ` Robin Murphy
2020-06-24 8:15 ` John Garry
2020-07-16 10:20 ` Will Deacon
2020-07-16 10:26 ` John Garry
2020-07-08 13:00 ` [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency John Garry
2020-07-16 10:19 ` Will Deacon
2020-07-16 10:22 ` Will Deacon
2020-07-16 10:28 ` Will Deacon
2020-07-16 10:56 ` John Garry
2020-07-16 11:22 ` Robin Murphy
2020-07-16 11:30 ` John Garry
2020-07-16 11:32 ` Will Deacon
2020-07-16 16:50 ` John Garry
2020-07-16 13:31 ` John Garry
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