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Subject: Re: [PATCH v13 4/6] iommu/vt-d: Add support for IOMMU default DMA
 mode build options
To:     John Garry <john.garry@huawei.com>, joro@8bytes.org,
        will@kernel.org, dwmw2@infradead.org, robin.murphy@arm.com,
        corbet@lwn.net
References: <1623841437-211832-1-git-send-email-john.garry@huawei.com>
 <1623841437-211832-5-git-send-email-john.garry@huawei.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <46dbce5c-1c2b-60d4-df56-d2b95a959425@linux.intel.com>
Date:   Thu, 17 Jun 2021 15:32:23 +0800
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On 6/16/21 7:03 PM, John Garry wrote:
> @@ -4382,9 +4380,9 @@ int __init intel_iommu_init(void)
>   		 * is likely to be much lower than the overhead of synchronizing
>   		 * the virtual and physical IOMMU page-tables.
>   		 */
> -		if (!intel_iommu_strict && cap_caching_mode(iommu->cap)) {
> -			pr_warn("IOMMU batching is disabled due to virtualization");
> -			intel_iommu_strict = 1;
> +		if (cap_caching_mode(iommu->cap)) {
> +			pr_warn("IOMMU batching disallowed due to virtualization\n");
> +			iommu_set_dma_strict(true);

With this change, VM guest will always show this warning. How about
removing this message? Users could get the same information through the
kernel message added by "[PATCH v13 2/6] iommu: Print strict or lazy
mode at init time".

Best regards,
baolu