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Thu, 21 Jan 2021 18:05:51 +0000 (UTC) Received: from omen.home.shazbot.org (ovpn-112-255.phx2.redhat.com [10.3.112.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1871360BF3; Thu, 21 Jan 2021 18:05:49 +0000 (UTC) Date: Thu, 21 Jan 2021 11:05:48 -0700 From: Alex Williamson To: Keqian Zhu Subject: Re: [PATCH v2 1/2] vfio/iommu_type1: Populate full dirty when detach non-pinned group Message-ID: <20210121110548.33f37048@omen.home.shazbot.org> In-Reply-To: References: <20210115092643.728-1-zhukeqian1@huawei.com> <20210115092643.728-2-zhukeqian1@huawei.com> <20210115110144.61e3c843@omen.home.shazbot.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_130601_331301_D7A78FD8 X-CRM114-Status: GOOD ( 29.59 ) 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: Mark Rutland , jiangkunkun@huawei.com, kvm@vger.kernel.org, Catalin Marinas , Kirti Wankhede , Will Deacon , kvmarm@lists.cs.columbia.edu, Marc Zyngier , Joerg Roedel , Daniel Lezcano , wanghaibin.wang@huawei.com, Julien Thierry , Suzuki K Poulose , Alexios Zavras , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Cornelia Huck , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, James Morse , Andrew Morton , 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 Mon, 18 Jan 2021 20:25:09 +0800 Keqian Zhu wrote: > On 2021/1/16 2:01, Alex Williamson wrote: > > On Fri, 15 Jan 2021 17:26:42 +0800 > > Keqian Zhu wrote: > > > >> If a group with non-pinned-page dirty scope is detached with dirty > >> logging enabled, we should fully populate the dirty bitmaps at the > >> time it's removed since we don't know the extent of its previous DMA, > >> nor will the group be present to trigger the full bitmap when the user > >> retrieves the dirty bitmap. > >> > >> Fixes: d6a4c185660c ("vfio iommu: Implementation of ioctl for dirty pages tracking") > >> Suggested-by: Alex Williamson > >> Signed-off-by: Keqian Zhu > >> --- > >> drivers/vfio/vfio_iommu_type1.c | 18 +++++++++++++++++- > >> 1 file changed, 17 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 0b4dedaa9128..4e82b9a3440f 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -236,6 +236,19 @@ static void vfio_dma_populate_bitmap(struct vfio_dma *dma, size_t pgsize) > >> } > >> } > >> > >> +static void vfio_iommu_populate_bitmap_full(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); > >> + > >> + if (dma->iommu_mapped) > >> + bitmap_set(dma->bitmap, 0, dma->size >> pgshift); > >> + } > >> +} > >> + > >> static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, size_t pgsize) > >> { > >> struct rb_node *n; > >> @@ -2415,8 +2428,11 @@ static void vfio_iommu_type1_detach_group(void *iommu_data, > >> * Removal of a group without dirty tracking may allow the iommu scope > >> * to be promoted. > >> */ > >> - if (update_dirty_scope) > >> + if (update_dirty_scope) { > >> update_pinned_page_dirty_scope(iommu); > >> + if (iommu->dirty_page_tracking) > >> + vfio_iommu_populate_bitmap_full(iommu); > >> + } > >> mutex_unlock(&iommu->lock); > >> } > >> > > > > This doesn't do the right thing. This marks the bitmap dirty if: > > > > * The detached group dirty scope was not limited to pinned pages > > > > AND > > > > * Dirty tracking is enabled > > > > AND > > > > * The vfio_dma is *currently* (ie. after the detach) iommu_mapped > > > > We need to mark the bitmap dirty based on whether the vfio_dma *was* > > iommu_mapped by the group that is now detached. Thanks, > > > > Alex > > > Hi Alex, > > Yes, I missed this point again :-(. The update_dirty_scope means we > detached an iommu backed group, and that means the vfio_dma *was* > iommu_mapped by this group, so we can populate full bitmap > unconditionally, right? To do it unconditionally, the assumption would be that all current vfio_dmas are iommu_mapped. It seems like it's deterministic that a non-pinned-page scope group implies all vfio_dmas are iommu_mapped. I can't currently think of an exception. Thanks, Alex _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel