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Tue, 15 Dec 2020 15:54:03 +0000 (UTC) Received: from x1.home (ovpn-112-193.phx2.redhat.com [10.3.112.193]) by smtp.corp.redhat.com (Postfix) with ESMTP id 917E81962E; Tue, 15 Dec 2020 15:54:00 +0000 (UTC) Date: Tue, 15 Dec 2020 08:53:59 -0700 From: Alex Williamson To: zhukeqian Subject: Re: [PATCH 4/7] vfio: iommu_type1: Fix missing dirty page when promote pinned_scope Message-ID: <20201215085359.053e73ed@x1.home> In-Reply-To: References: <20201210073425.25960-1-zhukeqian1@huawei.com> <20201210073425.25960-5-zhukeqian1@huawei.com> <20201214170459.50cb8729@omen.home> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201215_105415_167586_5277C5D6 X-CRM114-Status: GOOD ( 30.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jiangkunkun@huawei.com, Andrew Morton , kvm@vger.kernel.org, Suzuki K Poulose , Marc Zyngier , Joerg Roedel , Cornelia Huck , linux-kernel@vger.kernel.org, Sean Christopherson , Alexios Zavras , iommu@lists.linux-foundation.org, Mark Brown , James Morse , Julien Thierry , Catalin Marinas , wanghaibin.wang@huawei.com, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Robin Murphy Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 15 Dec 2020 17:37:11 +0800 zhukeqian wrote: > Hi Alex, > > On 2020/12/15 8:04, Alex Williamson wrote: > > On Thu, 10 Dec 2020 15:34:22 +0800 > > Keqian Zhu 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. > > > OK, I will. > > >> > >> Signed-off-by: Keqian Zhu > >> --- > >> 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, > > Good spot :-). The code will skip bitmap_set under this situation. > > We should set the bitmap unconditionally when vfio_iommu is promoted, > as we must have IOMMU backed domain before promoting the vfio_iommu. > > Besides, I think we should also mark dirty in vfio_remove_dma if dirty > tracking is active. Right? There's no remaining bitmap to mark dirty if the vfio_dma is removed. In this case it's the user's responsibility to collect remaining dirty pages using the VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP support in the VFIO_IOMMU_UNMAP_DMA ioctl. 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, > > > > . > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel