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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uzHpM-00000000gM8-3hO7; Thu, 18 Sep 2025 16:49:48 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uzHpK-00000000gLe-3kxH for linux-arm-kernel@lists.infradead.org; Thu, 18 Sep 2025 16:49:48 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 31EEB44744; Thu, 18 Sep 2025 16:49:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FAD2C4CEE7; Thu, 18 Sep 2025 16:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758214186; bh=8OuWAH6OvinDsM3HZFF+ftHMzLteFxBCpGaW+ema4Dc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XhkSqZ0RmKMoDqAaFQQbP8Dedsoke4YsdpJ+eT+BNeZBOKu6GoLC4mV5fyKlSj22V 7O0M1l7sGbCN1coRUo5Y128lXr8FnrJb+JB6tYZ2+H8A5EYXG99fgoGXtkNgj+c6Qm qNPM0lAXmCKkUqjXFZlCKmR7yieAEwWyAW6LAih45owBDXF6kqosW+POMFzAA6PacD 153lrIBqKlSGd6wlcFbCihifTBnEdEbNFwmwivOFJI+z8AukyS9luPcW9jQGQ5G1DL bxFMZMMUHVfWjU2lYn85Yv7UrECeA1J2GV6Tf7NCem2OafCWJ37XPnQOfszsdBOxdK 64C0fcYteJRug== Date: Thu, 18 Sep 2025 17:49:39 +0100 From: Will Deacon To: Shyam Saini Cc: thierry.reding@gmail.com, robin.murphy@arm.com, robh@kernel.org, joro@8bytes.org, jgg@ziepe.ca, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, virtualization@lists.linux.dev, jacob.pan@linux.microsoft.com, eric.auger@redhat.com, code@tyhicks.com, eahariha@linux.microsoft.com, vijayb@linux.microsoft.com, bboscaccy@linux.microsoft.com, saravanak@google.com, krzk+dt@kernel.org, conor+dt@kernel.org, lizhi.hou@amd.com, clement.leger@bootlin.com Subject: Re: [PATCH v4 3/4] arm-smmu: select suitable MSI IOVA Message-ID: References: <20250909154600.910110-1-shyamsaini@linux.microsoft.com> <20250909154600.910110-4-shyamsaini@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250909154600.910110-4-shyamsaini@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250918_094946_973996_49E38F96 X-CRM114-Status: GOOD ( 26.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 09, 2025 at 08:45:59AM -0700, Shyam Saini wrote: > Currently ARM SMMU drivers hardcode PCI MSI IOVA address. > Not all the platform have same memory mappings and some platform > could have this address already being mapped for something else. > This can lead to collision and as a consequence the MSI IOVA addr > range is never reserved. > > Fix this by reserving faulty IOVA range and selecting alternate MSI_IOVA > suitable for the intended platform. > > Example of reserving faulty IOVA range for PCIE device in the DTS: > > reserved-memory { > #address-cells = <2>; > #size-cells = <2>; > faulty_iova: resv_faulty { > iommu-addresses = <&pcieX 0x0 0x8000000 0x0 0x100000>; > }; > }; > > &pcieX { > memory-region = <&faulty_iova>; > } > > Suggested-by: Jason Gunthorpe > Signed-off-by: Shyam Saini > --- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 29 +++++++++++++----- > drivers/iommu/arm/arm-smmu/arm-smmu.c | 27 ++++++++++++----- > include/linux/iommu.h | 33 +++++++++++++++++++++ > 3 files changed, 75 insertions(+), 14 deletions(-) > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 2a8b46b948f05..748a5513c5dbb 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -3642,17 +3642,32 @@ static int arm_smmu_of_xlate(struct device *dev, > static void arm_smmu_get_resv_regions(struct device *dev, > struct list_head *head) > { > - struct iommu_resv_region *region; > int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO; > > - region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, > - prot, IOMMU_RESV_SW_MSI, GFP_KERNEL); > - if (!region) > - return; > - > - list_add_tail(®ion->list, head); > + static const u64 msi_bases[] = { MSI_IOVA_BASE, MSI_IOVA_BASE2 }; > > iommu_dma_get_resv_regions(dev, head); > + > + /* > + * Use the first msi_base that does not intersect with a platform > + * reserved region. The SW MSI base selection is entirely arbitrary. > + */ > + for (int i = 0; i != ARRAY_SIZE(msi_bases); i++) { > + struct iommu_resv_region *region; > + > + if (resv_region_intersects(msi_bases[i], MSI_IOVA_LENGTH, head)) > + continue; > + > + region = iommu_alloc_resv_region(msi_bases[i], MSI_IOVA_LENGTH, prot, > + IOMMU_RESV_SW_MSI, GFP_KERNEL); > + if (!region) { > + pr_warn("IOMMU: Failed to reserve MSI IOVA: No suitable MSI IOVA range available"); > + return; > + } > + > + list_add_tail(®ion->list, head); > + return; > + } > } > > /* > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c > index 4a07650911991..84b74b8519386 100644 > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c > @@ -1600,17 +1600,30 @@ static int arm_smmu_of_xlate(struct device *dev, > static void arm_smmu_get_resv_regions(struct device *dev, > struct list_head *head) > { > - struct iommu_resv_region *region; > int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO; > > - region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, > - prot, IOMMU_RESV_SW_MSI, GFP_KERNEL); > - if (!region) > - return; > - > - list_add_tail(®ion->list, head); > + static const u64 msi_bases[] = { MSI_IOVA_BASE, MSI_IOVA_BASE2 }; > > iommu_dma_get_resv_regions(dev, head); > + > + /* > + * Use the first msi_base that does not intersect with a platform > + * reserved region. The SW MSI base selection is entirely arbitrary. > + */ > + for (int i = 0; i != ARRAY_SIZE(msi_bases); i++) { > + struct iommu_resv_region *region; > + > + if (resv_region_intersects(msi_bases[i], MSI_IOVA_LENGTH, head)) > + continue; > + > + region = iommu_alloc_resv_region(msi_bases[i], MSI_IOVA_LENGTH, prot, > + IOMMU_RESV_SW_MSI, GFP_KERNEL); > + if (!region) > + return; > + > + list_add_tail(®ion->list, head); > + return; > + } Given that we're walking over the reserved regions to see if we have a collision with MSI_IOVA_BASE, why not allocate the base address dynamically if we detect a collision rather than having yet another hard-coded address which we can't guarantee won't be problematic in future? Will