Re: [PATCH 4/7] vfio: iommu_type1: Fix missing dirty page when promote pinned_scope

From: Alex Williamson <alex.williamson@redhat.com>
To: Keqian Zhu <zhukeqian1@huawei.com>
Cc: jiangkunkun@huawei.com, Andrew Morton <akpm@linux-foundation.org>,
	kvm@vger.kernel.org, Suzuki K Poulose <suzuki.poulose@arm.com>,
	Marc Zyngier <maz@kernel.org>, Joerg Roedel <joro@8bytes.org>,
	Cornelia Huck <cohuck@redhat.com>,
	linux-kernel@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Alexios Zavras <alexios.zavras@intel.com>,
	iommu@lists.linux-foundation.org, Mark Brown <broonie@kernel.org>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	wanghaibin.wang@huawei.com, Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 4/7] vfio: iommu_type1: Fix missing dirty page when promote pinned_scope
Date: Mon, 14 Dec 2020 17:04:59 -0700	[thread overview]
Message-ID: <20201214170459.50cb8729@omen.home> (raw)
In-Reply-To: <20201210073425.25960-5-zhukeqian1@huawei.com>

On Thu, 10 Dec 2020 15:34:22 +0800
Keqian Zhu <zhukeqian1@huawei.com> wrote:

> When we pin or detach a group which is not dirty tracking capable,
> we will try to promote pinned_scope of vfio_iommu.
> 
> If we succeed to do so, vfio only report pinned_scope as dirty to
> userspace next time, but these memory written before pin or detach
> is missed.
> 
> The solution is that we must populate all dma range as dirty before
> promoting pinned_scope of vfio_iommu.

Please don't bury fixes patches into a series with other optimizations
and semantic changes.  Send it separately.

> 
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index bd9a94590ebc..00684597b098 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1633,6 +1633,20 @@ static struct vfio_group *vfio_iommu_find_iommu_group(struct vfio_iommu *iommu,
>  	return group;
>  }
>  
> +static void vfio_populate_bitmap_all(struct vfio_iommu *iommu)
> +{
> +	struct rb_node *n;
> +	unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
> +
> +	for (n = rb_first(&iommu->dma_list); n; n = rb_next(n)) {
> +		struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> +		unsigned long nbits = dma->size >> pgshift;
> +
> +		if (dma->iommu_mapped)
> +			bitmap_set(dma->bitmap, 0, nbits);
> +	}
> +}

If we detach a group which results in only non-IOMMU backed mdevs,
don't we also clear dma->iommu_mapped as part of vfio_unmap_unpin()
such that this test is invalid?  Thanks,

Alex

> +
>  static void promote_pinned_page_dirty_scope(struct vfio_iommu *iommu)
>  {
>  	struct vfio_domain *domain;
> @@ -1657,6 +1671,10 @@ static void promote_pinned_page_dirty_scope(struct vfio_iommu *iommu)
>  	}
>  
>  	iommu->pinned_page_dirty_scope = true;
> +
> +	/* Set all bitmap to avoid missing dirty page */
> +	if (iommu->dirty_page_tracking)
> +		vfio_populate_bitmap_all(iommu);
>  }
>  
>  static bool vfio_iommu_has_sw_msi(struct list_head *group_resv_regions,

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