On 6/27/22 14:10, Russell Currey wrote:
On Thu, 2022-06-16 at 17:59 +1000, Alexey Kardashevskiy wrote:The pseries platform uses 32bit default DMA window (always 4K pages) and optional 64bit DMA window available via DDW ("Dynamic DMA Windows"), 64K or 2M pages. For ages the default one was not removed and a huge window was created in addition. Things changed with SRIOV-enabled PowerVM which creates a default-and-bigger DMA window in 64bit space (still using 4K pages) for IOV VFs so certain OSes do not need to use the DDW API in order to utilize all available TCE budget. Linux on the other hand removes the default window and creates a bigger one (with more TCEs or/and a bigger page size - 64K/2M) in a bid to map the entire RAM, and if the new window size is smaller than that - it still uses this new bigger window. The result is that the default window is removed but the "ibm,dma-window" property is not. When kdump is invoked, the existing code tries reusing the existing 64bit DMA window which location and parameters are stored in the device tree but this fails as the new property does not make it to the kdump device tree blob. So the code falls back to the default window which does not exist anymore although the device tree says that it does. The result of that is that PCI devices become unusable and cannot be used for kdumping. This preserves the DMA64 and DIRECT64 properties in the device tree blob for the crash kernel. Since the crash kernel setup is done after device drivers are loaded and probed, the proper DMA config is stored at least for boot time devices. Because DDW window is optional and the code configures the default window first, the existing code creates an IOMMU table descriptor for the non-existing default DMA window. It is harmless for kdump as it does not touch the actual window (only reads what is mapped and marks those IO pages as used) but it is bad for kexec which clears it thinking it is a smaller default window rather than a bigger DDW window. This removes the "ibm,dma-window" property from the device tree after a bigger window is created and the crash kernel setup picks it up. Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>Hey Alexey, great description of the problem. Would this need a Fixes: tag?
May be. But which patch does it fix really - the one which did not preserve the dma64 properties or the one which started removing the default window? :)
--- arch/powerpc/kexec/file_load_64.c | 52 +++++++++++++++ arch/powerpc/platforms/pseries/iommu.c | 88 +++++++++++++++--------- -- 2 files changed, 102 insertions(+), 38 deletions(-) diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c index b4981b651d9a..b4b486b68b63 100644 --- a/arch/powerpc/kexec/file_load_64.c +++ b/arch/powerpc/kexec/file_load_64.c @@ -1038,6 +1038,48 @@ static int update_cpus_node(void *fdt) return ret; }+static int copy_dma_property(void *fdt, int node_offset, conststruct device_node *dn, + const char *propname) +{ + const void *prop, *fdtprop; + int len = 0, fdtlen = 0, ret; + + prop = of_get_property(dn, propname, &len); + fdtprop = fdt_getprop(fdt, node_offset, propname, &fdtlen); + + if (fdtprop && !prop) + ret = fdt_delprop(fdt, node_offset, propname); + else if (prop) + ret = fdt_setprop(fdt, node_offset, propname, prop, len);If fdtprop and prop are both false, ret is returned uninitialised.+ + return ret; +} + +static int update_pci_nodes(void *fdt, const char *dmapropname) +{ + struct device_node *dn; + int pci_offset, root_offset, ret = 0; + + if (!firmware_has_feature(FW_FEATURE_LPAR)) + return 0; + + root_offset = fdt_path_offset(fdt, "/"); + for_each_node_with_property(dn, dmapropname) { + pci_offset = fdt_subnode_offset(fdt, root_offset, of_node_full_name(dn)); + if (pci_offset < 0) + continue; + + ret = copy_dma_property(fdt, pci_offset, dn, "ibm,dma-window"); + if (ret < 0) + break; + ret = copy_dma_property(fdt, pci_offset, dn, dmapropname); + if (ret < 0) + break; + } + + return ret; +} + /** * setup_new_fdt_ppc64 - Update the flattend device-tree of the kernel * being loaded. @@ -1099,6 +1141,16 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt, if (ret < 0) goto out;+#define DIRECT64_PROPNAME "linux,direct64-ddr-window-info"+#define DMA64_PROPNAME "linux,dma64-ddr-window-info"Instead of having these defined in two different places, could they be moved out of iommu.c and into a header? Though we hardcode ibm,dma- window everywhere anyway.
These properties are for pseries only and making them visible to other platforms seemed too much (I should have added #undef for those just below, to reduce visibility, I think). May be (may be) we want a ppc_md.kexec_update_fdt() hook but I dislike the whole ppc_md struct. Not sure.
+ ret = update_pci_nodes(fdt, DIRECT64_PROPNAME); + if (ret < 0) + goto out; + + ret = update_pci_nodes(fdt, DMA64_PROPNAME); + if (ret < 0) + goto out; + /* Update memory reserve map */ ret = get_reserved_memory_ranges(&rmem); if (ret) diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index fba64304e859..af3c871668df 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -700,6 +700,33 @@ struct iommu_table_ops iommu_table_lpar_multi_ops = { .get = tce_get_pSeriesLP };+/*+ * Find nearest ibm,dma-window (default DMA window) or direct DMA window or + * dynamic 64bit DMA window, walking up the device tree. + */ +static struct device_node *pci_dma_find(struct device_node *dn, + const __be32 **dma_window) +{ + const __be32 *dw = NULL; + + for ( ; dn && PCI_DN(dn); dn = dn->parent) { + dw = of_get_property(dn, "ibm,dma-window", NULL); + if (dw) { + if (dma_window) + *dma_window = dw; + return dn; + } + dw = of_get_property(dn, DIRECT64_PROPNAME, NULL); + if (dw) + return dn; + dw = of_get_property(dn, DMA64_PROPNAME, NULL); + if (dw) + return dn; + } + + return NULL; +} + static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus) { struct iommu_table *tbl; @@ -712,20 +739,10 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus) pr_debug("pci_dma_bus_setup_pSeriesLP: setting up bus %pOF\n", dn);- /*- * Find nearest ibm,dma-window (default DMA window), walking up the - * device tree - */ - for (pdn = dn; pdn != NULL; pdn = pdn->parent) { - dma_window = of_get_property(pdn, "ibm,dma-window", NULL); - if (dma_window != NULL) - break; - } + pdn = pci_dma_find(dn, &dma_window);- if (dma_window == NULL) {+ if (dma_window == NULL) pr_debug(" no ibm,dma-window property !\n"); - return; - }ppci = PCI_DN(pdn); @@ -735,11 +752,13 @@ static void pci_dma_bus_setup_pSeriesLP(structpci_bus *bus) if (!ppci->table_group) { ppci->table_group = iommu_pseries_alloc_group(ppci-phb->node);tbl = ppci->table_group->tables[0]; - iommu_table_setparms_lpar(ppci->phb, pdn, tbl, - ppci->table_group, dma_window); + if (dma_window) { + iommu_table_setparms_lpar(ppci->phb, pdn, tbl, + ppci->table_group, dma_window);- if (!iommu_init_table(tbl, ppci->phb->node, 0, 0))- panic("Failed to initialize iommu table"); + if (!iommu_init_table(tbl, ppci->phb->node, 0, 0)) + panic("Failed to initialize iommu table"); + } iommu_register_group(ppci->table_group, pci_domain_nr(bus), 0); pr_debug(" created table: %p\n", ppci->table_group); @@ -1429,16 +1448,22 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)pci->table_group->tables[1] = newtbl; - /* Keep default DMA window struct if removed */- if (default_win_removed) { - tbl->it_size = 0; - vfree(tbl->it_map); - tbl->it_map = NULL; - } - set_iommu_table_base(&dev->dev, newtbl); }+ if (default_win_removed) {+ struct property *def_win;Another section of enable_ddw() already has a default_win, could that variable be made top-level and shared?
Oh. Yes it can be shared, v2 is coming.
+ struct pci_dn *pci = PCI_DN(pdn);enable_ddw() already has the same variable declared.Otherwise, LGTM.Reviewed-by: Russell Currey <rus...@russell.cc>
Thanks!
+ + iommu_tce_table_put(pci->table_group->tables[0]); + def_win = of_find_property(pdn, "ibm,dma-window", NULL); + if (def_win) { + of_remove_property(pdn, def_win); + dev_info(&dev->dev, "Removed default DMA window for %pOF\n", pdn); + } + pci->table_group->tables[0] = NULL; + } + spin_lock(&dma_win_list_lock); list_add(&window->list, &dma_win_list); spin_unlock(&dma_win_list_lock); @@ -1503,13 +1528,7 @@ static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev) dn = pci_device_to_OF_node(dev); pr_debug(" node is %pOF\n", dn);- for (pdn = dn; pdn && PCI_DN(pdn) && !PCI_DN(pdn)-table_group;- pdn = pdn->parent) { - dma_window = of_get_property(pdn, "ibm,dma-window", NULL); - if (dma_window) - break; - } - + pdn = pci_dma_find(dn, &dma_window); if (!pdn || !PCI_DN(pdn)) { printk(KERN_WARNING "pci_dma_dev_setup_pSeriesLP: " "no DMA window found for pci dev=%s dn=%pOF\n", @@ -1540,7 +1559,6 @@ static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev) static bool iommu_bypass_supported_pSeriesLP(struct pci_dev *pdev, u64 dma_mask) { struct device_node *dn = pci_device_to_OF_node(pdev), *pdn; - const __be32 *dma_window = NULL;/* only attempt to use a new window if 64-bit DMA isrequested */ if (dma_mask < DMA_BIT_MASK(64)) @@ -1554,13 +1572,7 @@ static bool iommu_bypass_supported_pSeriesLP(struct pci_dev *pdev, u64 dma_mask) * search upwards in the tree until we either hit a dma- window * property, OR find a parent with a table already allocated. */ - for (pdn = dn; pdn && PCI_DN(pdn) && !PCI_DN(pdn)-table_group;- pdn = pdn->parent) { - dma_window = of_get_property(pdn, "ibm,dma-window", NULL); - if (dma_window) - break; - } - + pdn = pci_dma_find(dn, NULL); if (pdn && PCI_DN(pdn)) return enable_ddw(pdev, pdn);
-- Alexey
