From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Fri, 25 Feb 2022 08:47:55 +0000 Subject: Re: cleanup swiotlb initialization Message-Id: <20220225084755.GA29630@lst.de> List-Id: References: <20220222153514.593231-1-hch@lst.de> <09cb4ad3-88e7-3744-b4b8-a6d745ecea9e@oracle.com> <20220224155854.GA30938@lst.de> <206ba6a3-770a-70ad-96bc-76c6380da988@oracle.com> <20220224163943.GA32088@lst.de> <8ffd8587-7eb3-d5b6-eab0-b86df5c0ebbd@oracle.com> In-Reply-To: <8ffd8587-7eb3-d5b6-eab0-b86df5c0ebbd@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Boris Ostrovsky Cc: Christoph Hellwig , iommu@lists.linux-foundation.org, x86@kernel.org, Stefano Stabellini , Juergen Gross , Joerg Roedel , David Woodhouse , Lu Baolu , Robin Murphy , linux-arm-kernel@lists.infradead.org, xen-devel@lists.xenproject.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-hyperv@vger.kernel.org, tboot-devel@lists.sourceforge.net, linux-pci@vger.kernel.org On Thu, Feb 24, 2022 at 12:07:26PM -0500, Boris Ostrovsky wrote: >>> Just to be clear: this crashes only as dom0. Boots fine as baremetal. >> Ah. I can gues what this might be. On Xen the hypervisor controls the >> IOMMU and we should never end up initializing it in Linux, right? > > > Right, we shouldn't be in that code path. Can you try the patch below on top of the series? diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index b849f11a756d0..f88c9a4a5ed12 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -47,22 +47,6 @@ static unsigned int x86_swiotlb_flags; */ static void __init pci_swiotlb_detect_4gb(void) { -#ifdef CONFIG_SWIOTLB_XEN - if (xen_pv_domain()) { - if (xen_initial_domain()) - x86_swiotlb_enable = true; - - if (x86_swiotlb_enable) { - dma_ops = &xen_swiotlb_dma_ops; -#ifdef CONFIG_PCI - /* Make sure ACS will be enabled */ - pci_request_acs(); -#endif - } - return; - } -#endif /* CONFIG_SWIOTLB_XEN */ - /* don't initialize swiotlb if iommu=off (no_iommu=1) */ if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN) x86_swiotlb_enable = true; @@ -82,16 +66,36 @@ static inline void __init pci_swiotlb_detect_4gb(void) } #endif /* CONFIG_SWIOTLB */ +#ifdef CONFIG_SWIOTLB_XEN +static void __init xen_swiotlb_init(void) +{ + if (!xen_initial_domain() && !x86_swiotlb_enable) + return; + x86_swiotlb_enable = true; + dma_ops = &xen_swiotlb_dma_ops; +#ifdef CONFIG_PCI + /* Make sure ACS will be enabled */ + pci_request_acs(); +#endif + swiotlb_init_remap(true, x86_swiotlb_flags, xen_swiotlb_fixup); +} +#else +static inline void __init xen_swiotlb_init(void) +{ +} +#endif /* CONFIG_SWIOTLB_XEN */ + void __init pci_iommu_alloc(void) { + if (xen_pv_domain()) { + xen_swiotlb_init(); + return; + } pci_swiotlb_detect_4gb(); gart_iommu_hole_init(); amd_iommu_detect(); detect_intel_iommu(); -#ifdef CONFIG_SWIOTLB - swiotlb_init_remap(x86_swiotlb_enable, x86_swiotlb_flags, - xen_pv_domain() ? xen_swiotlb_fixup : NULL); -#endif + swiotlb_init(x86_swiotlb_enable, x86_swiotlb_flags); } /*