Re: [PATCH RFC 5/8] iommu/arm-smmu-v3: Add support for ECMDQ register mode

[Leizhen (ThunderTown) <thunder.leizhen@huawei.com>]

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On 2021/6/26 23:49, kernel test robot wrote:
> Hi Zhen,
> 
> [FYI, it's a private test report for your RFC patch.]
> [auto build test WARNING on iommu/next]
> [also build test WARNING on arm-perf/for-next/perf v5.13-rc7 next-20210625]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in

OK, these patches is based on the latest linux-next.

> https://git-scm.com/docs/git-format-patch]
> 
> url:    https://github.com/0day-ci/linux/commits/Zhen-Lei/iommu-arm-smmu-v3-add-support-for-ECMDQ-register-mode/20210626-190316
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git next
> config: arm64-randconfig-r032-20210622 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 557b101ce714e39438ba1d39c4c50b03e12fcb96)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install arm64 cross compiling tool for clang build
>         # apt-get install binutils-aarch64-linux-gnu
>         # https://github.com/0day-ci/linux/commit/fb36a6675f695ca24d94d461a7a6521e4d798226
>         git remote add linux-review https://github.com/0day-ci/linux
>         git fetch --no-tags linux-review Zhen-Lei/iommu-arm-smmu-v3-add-support-for-ECMDQ-register-mode/20210626-190316
>         git checkout fb36a6675f695ca24d94d461a7a6521e4d798226
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c:3578:39: warning: variable 'pre_addr' is uninitialized when used here [-Wuninitialized]
>                    if (i && ((val & ECMDQ_CP_ADDR) != (pre_addr + ECMDQ_CP_RRESET_SIZE))) {
>                                                        ^~~~~~~~
>    drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c:3569:20: note: initialize the variable 'pre_addr' to silence this warning
>                    u64 val, pre_addr;
>                                     ^
>                                      = 0
>    1 warning generated.
> 
> 
> vim +/pre_addr +3578 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> 
>   3547	
>   3548	static int arm_smmu_ecmdq_probe(struct arm_smmu_device *smmu)
>   3549	{
>   3550		int ret, cpu;
>   3551		u32 i, nump, numq, gap;
>   3552		u32 reg, shift_increment;
>   3553		u64 addr, smmu_dma_base;
>   3554		void __iomem *cp_regs, *cp_base;
>   3555	
>   3556		/* IDR6 */
>   3557		reg = readl_relaxed(smmu->base + ARM_SMMU_IDR6);
>   3558		nump = 1 << FIELD_GET(IDR6_LOG2NUMP, reg);
>   3559		numq = 1 << FIELD_GET(IDR6_LOG2NUMQ, reg);
>   3560		smmu->nr_ecmdq = nump * numq;
>   3561		gap = ECMDQ_CP_RRESET_SIZE >> FIELD_GET(IDR6_LOG2NUMQ, reg);
>   3562	
>   3563		smmu_dma_base = (vmalloc_to_pfn(smmu->base) << PAGE_SHIFT);
>   3564		cp_regs = ioremap(smmu_dma_base + ARM_SMMU_ECMDQ_CP_BASE, PAGE_SIZE);
>   3565		if (!cp_regs)
>   3566			return -ENOMEM;
>   3567	
>   3568		for (i = 0; i < nump; i++) {
>   3569			u64 val, pre_addr;
>   3570	
>   3571			val = readq_relaxed(cp_regs + 32 * i);
>   3572			if (!(val & ECMDQ_CP_PRESET)) {
>   3573				iounmap(cp_regs);
>   3574				dev_err(smmu->dev, "ecmdq control page %u is memory mode\n", i);
>   3575				return -EFAULT;
>   3576			}
>   3577	
>> 3578			if (i && ((val & ECMDQ_CP_ADDR) != (pre_addr + ECMDQ_CP_RRESET_SIZE))) {

The condition 'i' ensures that 'pre_addr' is not used in the first cycle(i==0).
It seems necessary to add "= 0" to initialize 'pre_addr' to eliminate this false positive.

>   3579				iounmap(cp_regs);
>   3580				dev_err(smmu->dev, "ecmdq_cp memory region is not contiguous\n");
>   3581				return -EFAULT;
>   3582			}
>   3583	
>   3584			pre_addr = val & ECMDQ_CP_ADDR;
>   3585		}
>   3586	
>   3587		addr = readl_relaxed(cp_regs) & ECMDQ_CP_ADDR;
>   3588		iounmap(cp_regs);
>   3589	
>   3590		cp_base = devm_ioremap(smmu->dev, smmu_dma_base + addr, ECMDQ_CP_RRESET_SIZE * nump);
>   3591		if (!cp_base)
>   3592			return -ENOMEM;
>   3593	
>   3594		smmu->ecmdq = devm_alloc_percpu(smmu->dev, struct arm_smmu_ecmdq *);
>   3595		if (!smmu->ecmdq)
>   3596			return -ENOMEM;
>   3597	
>   3598		ret = arm_smmu_ecmdq_layout(smmu);
>   3599		if (ret)
>   3600			return ret;
>   3601	
>   3602		shift_increment = order_base_2(num_possible_cpus() / smmu->nr_ecmdq);
>   3603	
>   3604		addr = 0;
>   3605		for_each_possible_cpu(cpu) {
>   3606			struct arm_smmu_ecmdq *ecmdq;
>   3607			struct arm_smmu_queue *q;
>   3608	
>   3609			ecmdq = *per_cpu_ptr(smmu->ecmdq, cpu);
>   3610			ecmdq->base = cp_base + addr;
>   3611	
>   3612			q = &ecmdq->cmdq.q;
>   3613	
>   3614			q->llq.max_n_shift = ECMDQ_MAX_SZ_SHIFT + shift_increment;
>   3615			ret = arm_smmu_init_one_queue(smmu, q, ecmdq->base, ARM_SMMU_ECMDQ_PROD,
>   3616					ARM_SMMU_ECMDQ_CONS, CMDQ_ENT_DWORDS, "ecmdq");
>   3617			if (ret)
>   3618				return ret;
>   3619	
>   3620			q->ecmdq_prod = ECMDQ_PROD_EN;
>   3621			rwlock_init(&q->ecmdq_lock);
>   3622	
>   3623			ret = arm_smmu_ecmdq_init(&ecmdq->cmdq);
>   3624			if (ret) {
>   3625				dev_err(smmu->dev, "ecmdq[%d] init failed\n", i);
>   3626				return ret;
>   3627			}
>   3628	
>   3629			addr += gap;
>   3630		}
>   3631	
>   3632		return 0;
>   3633	}
>   3634	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
>