linux-kernel - Re: [PATCH v3 1/2] iommu/arm-smmu-v3: fix unexpected CMD

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Message-ID: <20180816091805.GB31093@arm.com>
Date:   Thu, 16 Aug 2018 10:18:05 +0100
From:   Will Deacon <will.deacon@....com>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        LinuxArm <linuxarm@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Libin <huawei.libin@...wei.com>,
        John Garry <john.garry@...wei.com>
Subject: Re: [PATCH v3 1/2] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout

On Thu, Aug 16, 2018 at 04:21:17PM +0800, Leizhen (ThunderTown) wrote:
> On 2018/8/15 20:26, Robin Murphy wrote:
> > On 15/08/18 11:23, Zhen Lei wrote:
> >> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> >> index 1d64710..3f5c236 100644
> >> --- a/drivers/iommu/arm-smmu-v3.c
> >> +++ b/drivers/iommu/arm-smmu-v3.c
> >> @@ -566,7 +566,7 @@ struct arm_smmu_device {
> >>
> >>       int                gerr_irq;
> >>       int                combined_irq;
> >> -    atomic_t            sync_nr;
> >> +    u32                sync_nr;
> >>
> >>       unsigned long            ias; /* IPA */
> >>       unsigned long            oas; /* PA */
> >> @@ -775,6 +775,11 @@ static int queue_remove_raw(struct arm_smmu_queue *q, u64 *ent)
> >>       return 0;
> >>   }
> >>
> >> +static inline void arm_smmu_cmdq_sync_set_msidata(u64 *cmd, u32 msidata)
> > 
> > If we *are* going to go down this route then I think it would make sense
> > to move the msiaddr and CMDQ_SYNC_0_CS_MSI logic here as well; i.e.
> > arm_smmu_cmdq_build_cmd() always generates a "normal" SEV-based sync
> > command, then calling this guy would convert it to an MSI-based one.
> > As-is, having bits of mutually-dependent data handled across two
> > separate places just seems too messy and error-prone.
> 
> Yes, How about create a new function "arm_smmu_cmdq_build_sync_msi_cmd"?
> 
> static inline
> void arm_smmu_cmdq_build_sync_msi_cmd(u64 *cmd, struct arm_smmu_cmdq_ent *ent)
> {
> 	cmd[0]  = FIELD_PREP(CMDQ_0_OP, ent->opcode);
> 	cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_IRQ);
> 	cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH);
> 	cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB);
> 	cmd[1]  = ent->sync.msiaddr & CMDQ_SYNC_1_MSIADDR_MASK;
> }

None of this seems justified given the numbers from John, so please just do
the simple thing and build the command with the lock held.

Will