Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Arvind Sankar <nivedita@alum.mit.edu>
Date:   Mon, 7 Oct 2019 14:32:07 -0400
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Christoph Hellwig <hch@lst.de>, linux-kernel@vger.kernel.org
Subject: Re: ehci-pci breakage with dma-mapping changes in 5.4-rc2
Message-ID: <20191007183206.GA13589@rani.riverdale.lan>
References: <20191007022454.GA5270@rani.riverdale.lan>
 <20191007073448.GA882@lst.de>
 <20191007175430.GA32537@rani.riverdale.lan>
 <20191007175528.GA21857@lst.de>
 <20191007175630.GA28861@infradead.org>
 <20191007175856.GA42018@rani.riverdale.lan>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="ReaqsoxgOBHFXBhH"
Content-Disposition: inline
In-Reply-To: <20191007175856.GA42018@rani.riverdale.lan>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


--ReaqsoxgOBHFXBhH
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline

On Mon, Oct 07, 2019 at 01:58:57PM -0400, Arvind Sankar wrote:
> On Mon, Oct 07, 2019 at 10:56:30AM -0700, Christoph Hellwig wrote:
> > On Mon, Oct 07, 2019 at 07:55:28PM +0200, Christoph Hellwig wrote:
> > > On Mon, Oct 07, 2019 at 01:54:32PM -0400, Arvind Sankar wrote:
> > > > It doesn't boot with the patch. Won't it go
> > > > 	dma_get_required_mask
> > > > 	-> intel_get_required_mask
> > > > 	-> iommu_need_mapping
> > > > 	-> dma_get_required_mask
> > > > ?
> > > > 
> > > > Should the call to dma_get_required_mask in iommu_need_mapping be
> > > > replaced with dma_direct_get_required_mask on top of your patch?
> > > 
> > > Yes, sorry.
> > 
> > Actually my patch already calls dma_direct_get_required_mask.
> > How did you get the loop?
> 
> The function iommu_need_mapping (not changed by your patch) calls
> dma_get_required_mask internally, to check whether the device's dma_mask
> is big enough or not. That's the call I was asking whether it needs to
> be changed.

Yeah the attached patch seems to fix it.

--ReaqsoxgOBHFXBhH
Content-Type: text/x-diff; charset=utf-8
Content-Disposition: attachment; filename="0001-iommu-vt-d-Return-the-correct-dma-mask-when-we-are-b.patch"

From 074e8cc145dde514427c40124913a90c4552dd6e Mon Sep 17 00:00:00 2001
From: Arvind Sankar <nivedita@alum.mit.edu>
Date: Mon, 7 Oct 2019 14:19:12 -0400
Subject: [PATCH] iommu/vt-d: Return the correct dma mask when we are bypassing
 the IOMMU

We must return a mask covering the full physical RAM when bypassing the
IOMMU mapping. Also, in iommu_need_mapping, we need to check using
dma_direct_get_required_mask to ensure that the device's dma_mask can
cover physical RAM before deciding to bypass IOMMU mapping.

Fixes: 249baa547901 ("dma-mapping: provide a better default ->get_required_mask")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 drivers/iommu/intel-iommu.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 3f974919d3bd..79e35b3180ac 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3471,7 +3471,7 @@ static bool iommu_need_mapping(struct device *dev)
 		if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
 			dma_mask = dev->coherent_dma_mask;
 
-		if (dma_mask >= dma_get_required_mask(dev))
+		if (dma_mask >= dma_direct_get_required_mask(dev))
 			return false;
 
 		/*
@@ -3775,6 +3775,13 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
 	return nelems;
 }
 
+static u64 intel_get_required_mask(struct device *dev)
+{
+	if (!iommu_need_mapping(dev))
+		return dma_direct_get_required_mask(dev);
+	return DMA_BIT_MASK(32);
+}
+
 static const struct dma_map_ops intel_dma_ops = {
 	.alloc = intel_alloc_coherent,
 	.free = intel_free_coherent,
@@ -3787,6 +3794,7 @@ static const struct dma_map_ops intel_dma_ops = {
 	.dma_supported = dma_direct_supported,
 	.mmap = dma_common_mmap,
 	.get_sgtable = dma_common_get_sgtable,
+	.get_required_mask = intel_get_required_mask,
 };
 
 static void
-- 
2.21.0


--ReaqsoxgOBHFXBhH--