| Message ID | 20220629060614.1680476-1-aik@ozlabs.ru (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [kernel,v2] pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 23 jobs. |
On 29/06/22 11:36 am, 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. > Fixes: 381ceda88c4c ("powerpc/pseries/iommu: Make use of DDW for indirect mapping") > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Maybe another day but one more reason why fdt should be prepared from the current unflatted dt instead of initial_boot_params. .. Anyway, the patch looks good to me.. Acked-by: Hari Bathini <hbathini@linux.ibm.com> > --- > > Looks like SYSCALL(kexec_file_load) never supported DMA. so it could be: > Fixes: a0458284f062 ("powerpc: Add support code for kexec_file_load()") > > --- > Changes: > v2: > * reworked enable_ddw() to reuse default_win > * removed @tbl as it was only used once and later on this zeroes it > * undef for xxx64_PROPNAME in file_load_64.c > * renamed new functions in file_load_64.c > --- > arch/powerpc/kexec/file_load_64.c | 54 ++++++++++++++++ > arch/powerpc/platforms/pseries/iommu.c | 89 ++++++++++++++------------ > 2 files changed, 102 insertions(+), 41 deletions(-) > > diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c > index b4981b651d9a..5d2c22aa34fb 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_property(void *fdt, int node_offset, const struct 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); > + > + return ret; > +} > + > +static int update_pci_dma_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_property(fdt, pci_offset, dn, "ibm,dma-window"); > + if (ret < 0) > + break; > + ret = copy_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 +1141,18 @@ 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" > + ret = update_pci_dma_nodes(fdt, DIRECT64_PROPNAME); > + if (ret < 0) > + goto out; > + > + ret = update_pci_dma_nodes(fdt, DMA64_PROPNAME); > + if (ret < 0) > + goto out; > +#undef DMA64_PROPNAME > +#undef DIRECT64_PROPNAME > + > /* 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..c3d425ef7b39 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(struct pci_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); > @@ -1232,7 +1251,7 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) > bool default_win_removed = false, direct_mapping = false; > bool pmem_present; > struct pci_dn *pci = PCI_DN(pdn); > - struct iommu_table *tbl = pci->table_group->tables[0]; > + struct property *default_win = NULL; > > dn = of_find_node_by_type(NULL, "ibm,pmemory"); > pmem_present = dn != NULL; > @@ -1289,11 +1308,10 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) > * for extensions presence. > */ > if (query.windows_available == 0) { > - struct property *default_win; > int reset_win_ext; > > /* DDW + IOMMU on single window may fail if there is any allocation */ > - if (iommu_table_in_use(tbl)) { > + if (iommu_table_in_use(pci->table_group->tables[0])) { > dev_warn(&dev->dev, "current IOMMU table in use, can't be replaced.\n"); > goto out_failed; > } > @@ -1429,16 +1447,18 @@ 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) { > + iommu_tce_table_put(pci->table_group->tables[0]); > + pci->table_group->tables[0] = NULL; > + > + /* default_win is valid here because default_win_removed == true */ > + of_remove_property(pdn, default_win); > + dev_info(&dev->dev, "Removed default DMA window for %pOF\n", pdn); > + } > + > spin_lock(&dma_win_list_lock); > list_add(&window->list, &dma_win_list); > spin_unlock(&dma_win_list_lock); > @@ -1503,13 +1523,7 @@ 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 +1554,6 @@ 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 is requested */ > if (dma_mask < DMA_BIT_MASK(64)) > @@ -1554,13 +1567,7 @@ 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); >
On Wed, 29 Jun 2022 16:06:14 +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. > > [...] Applied to powerpc/next. [1/1] pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window https://git.kernel.org/powerpc/c/b1fc44eaa9ba31e28c4125d6b9205a3582b47b5d cheers
Hi Alexey,
This change is now in mainline as commit b1fc44eaa9ba
("pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window").
> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
> index b4981b651d9a..5d2c22aa34fb 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_property(void *fdt, int node_offset, const struct 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);
> +
> + return ret;
> +}
clang now warns/errors:
arch/powerpc/kexec/file_load_64.c:1053:11: error: variable 'ret' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
else if (prop)
^~~~
arch/powerpc/kexec/file_load_64.c:1056:9: note: uninitialized use occurs here
return ret;
^~~
arch/powerpc/kexec/file_load_64.c:1053:7: note: remove the 'if' if its condition is always true
else if (prop)
^~~~~~~~~
arch/powerpc/kexec/file_load_64.c:1046:30: note: initialize the variable 'ret' to silence this warning
int len = 0, fdtlen = 0, ret;
^
= 0
1 error generated.
Is !fdtprop && !prop a concern? What should a sensible default for ret
be?
Cheers,
Nathan
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c index b4981b651d9a..5d2c22aa34fb 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_property(void *fdt, int node_offset, const struct 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); + + return ret; +} + +static int update_pci_dma_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_property(fdt, pci_offset, dn, "ibm,dma-window"); + if (ret < 0) + break; + ret = copy_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 +1141,18 @@ 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" + ret = update_pci_dma_nodes(fdt, DIRECT64_PROPNAME); + if (ret < 0) + goto out; + + ret = update_pci_dma_nodes(fdt, DMA64_PROPNAME); + if (ret < 0) + goto out; +#undef DMA64_PROPNAME +#undef DIRECT64_PROPNAME + /* 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..c3d425ef7b39 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(struct pci_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); @@ -1232,7 +1251,7 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) bool default_win_removed = false, direct_mapping = false; bool pmem_present; struct pci_dn *pci = PCI_DN(pdn); - struct iommu_table *tbl = pci->table_group->tables[0]; + struct property *default_win = NULL; dn = of_find_node_by_type(NULL, "ibm,pmemory"); pmem_present = dn != NULL; @@ -1289,11 +1308,10 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) * for extensions presence. */ if (query.windows_available == 0) { - struct property *default_win; int reset_win_ext; /* DDW + IOMMU on single window may fail if there is any allocation */ - if (iommu_table_in_use(tbl)) { + if (iommu_table_in_use(pci->table_group->tables[0])) { dev_warn(&dev->dev, "current IOMMU table in use, can't be replaced.\n"); goto out_failed; } @@ -1429,16 +1447,18 @@ 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) { + iommu_tce_table_put(pci->table_group->tables[0]); + pci->table_group->tables[0] = NULL; + + /* default_win is valid here because default_win_removed == true */ + of_remove_property(pdn, default_win); + dev_info(&dev->dev, "Removed default DMA window for %pOF\n", pdn); + } + spin_lock(&dma_win_list_lock); list_add(&window->list, &dma_win_list); spin_unlock(&dma_win_list_lock); @@ -1503,13 +1523,7 @@ 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 +1554,6 @@ 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 is requested */ if (dma_mask < DMA_BIT_MASK(64)) @@ -1554,13 +1567,7 @@ 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);
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. Fixes: 381ceda88c4c ("powerpc/pseries/iommu: Make use of DDW for indirect mapping") Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- Looks like SYSCALL(kexec_file_load) never supported DMA. so it could be: Fixes: a0458284f062 ("powerpc: Add support code for kexec_file_load()") --- Changes: v2: * reworked enable_ddw() to reuse default_win * removed @tbl as it was only used once and later on this zeroes it * undef for xxx64_PROPNAME in file_load_64.c * renamed new functions in file_load_64.c --- arch/powerpc/kexec/file_load_64.c | 54 ++++++++++++++++ arch/powerpc/platforms/pseries/iommu.c | 89 ++++++++++++++------------ 2 files changed, 102 insertions(+), 41 deletions(-)