From: Henry Willard <henry.willard@oracle.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Kevin Tian <kevin.tian@intel.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] iommu: Avoid unnecessary cache invalidations
Date: Fri, 27 Oct 2023 04:30:31 +0000 [thread overview]
Message-ID: <196E8628-C1F4-4392-BFDC-BDA2B0D0835C@oracle.com> (raw)
In-Reply-To: <20231026084942.17387-1-baolu.lu@linux.intel.com>
On Oct 26, 2023, at 1:49 AM, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>
> The iommu_create_device_direct_mappings() only needs to flush the caches
> when the mappings are changed in the affected domain. This is not true
> for non-DMA domains, or for devices attached to the domain that have no
> reserved regions. To avoid unnecessary cache invalidations, add a check
> before iommu_flush_iotlb_all().
This also fixes a boot failure on Sapphire Rapids built with
CONFIG_IOMMU_DEFAULT_PASSTHROUGH=y or the equivalent via
kernel command line parameters.
>
> Fixes: a48ce36e2786 ("iommu: Prevent RESV_DIRECT devices from blocking domains")
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Henry Willard <henry.willard@oracle.com>
> ---
> drivers/iommu/iommu.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 00d0a2b5d7dc..0cb676590bfa 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1114,7 +1114,8 @@ static int iommu_create_device_direct_mappings(struct iommu_domain *domain,
>
> }
>
> - iommu_flush_iotlb_all(domain);
> + if (!list_empty(&mappings) && iommu_is_dma_domain(domain))
> + iommu_flush_iotlb_all(domain);
>
> out:
> iommu_put_resv_regions(dev, &mappings);
> --
> 2.34.1
>
>
next prev parent reply other threads:[~2023-10-27 4:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-26 8:49 [PATCH 1/1] iommu: Avoid unnecessary cache invalidations Lu Baolu
2023-10-27 4:30 ` Henry Willard [this message]
2023-10-27 6:57 ` Joerg Roedel
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