linux-kernel - Re: [PATCH] iommu/vt-d: Flush old iotlb for kdump when the device gets context mapped

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Message-ID: <20161201103307.GL2078@8bytes.org>
Date:   Thu, 1 Dec 2016 11:33:07 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     xlpang@...hat.com
Cc:     Baoquan He <bhe@...hat.com>, Don Brace <don.brace@...rosemi.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        kexec@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org,
        Myron Stowe <myron.stowe@...il.com>,
        Dave Young <dyoung@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] iommu/vt-d: Flush old iotlb for kdump when the device
 gets context mapped

On Thu, Dec 01, 2016 at 10:15:45AM +0800, Xunlei Pang wrote:
> index 3965e73..624eac9 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2024,6 +2024,25 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
>         if (context_present(context))
>                 goto out_unlock;
>  
> +       /*
> +        * For kdump cases, old valid entries may be cached due to the
> +        * in-flight DMA and copied pgtable, but there is no unmapping
> +        * behaviour for them, thus we need an explicit cache flush for
> +        * the newly-mapped device. For kdump, at this point, the device
> +        * is supposed to finish reset at its driver probe stage, so no
> +        * in-flight DMA will exist, and we don't need to worry anymore
> +        * hereafter.
> +        */
> +       if (context_copied(context)) {
> +               u16 did_old = context_domain_id(context);
> +
> +               if (did_old >= 0 && did_old < cap_ndoms(iommu->cap))
> +                       iommu->flush.flush_context(iommu, did_old,
> +                                                  (((u16)bus) << 8) | devfn,
> +                                                  DMA_CCMD_MASK_NOBIT,
> +                                                  DMA_CCMD_DEVICE_INVL);
> +       }
> +
>         pgd = domain->pgd;

Yes, this looks better. Have you tested it the same way as the old
patch?


	Joerg