Re: [PATCH v2] iommu/amd: Make PerfOpt compulsory

[Vasant Hegde <vasant.hegde@amd.com>]

On 9/30/2026 7:09 PM, Mario Limonciello wrote:
> On 9/30/26 04:38, Vasant Hegde wrote:
>> Mario,
>>

.../...

>>> +    u32 old, val, readback;
>>> +
>>> +    if (!check_feature(FEATURE_PERF_OPT))
>>> +        return enable ? -ENODEV : 0;
>>> +
>>> +    old = readl(iommu->mmio_base + MMIO_PERF_OPT_OFFSET);
>>> +    if (old == U32_MAX)
>>> +        return -EIO;
>>> +
>>> +    val = enable ? old | PERF_OPT_EN : old & ~PERF_OPT_EN;
>>> +    if (val != old)
>>> +        writel(val, iommu->mmio_base + MMIO_PERF_OPT_OFFSET);
>>> +    readback = readl(iommu->mmio_base + MMIO_PERF_OPT_OFFSET);
>>> +    if (readback == U32_MAX ||
>>> +        (readback & PERF_OPT_EN) != (val & PERF_OPT_EN)) {
>>> +        dev_err(iommu->iommu.dev, "Failed to set PerfOpt to %d\n", enable);
>>> +        return -EIO;
>>> +    }
>>> +
>>
>> May be check return value before enabling dev_data->perfopt?
> 
> I thought about this.
> 
> Let me know what you think of the approach of clearing the bit in amd_iommu_efr
> on failures within amd_iommu_perfopt_set().

Yeah. It makes sense.

-Vasant