| Message ID | 20191015191610.28680-1-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Xen-devel,for-4.13,v3] xen/arm: mm: Allow generic xen page-tables helpers to be called early | expand |
On Tue, 15 Oct 2019, Julien Grall wrote: > The current implementations of xen_{map, unmap}_table() expect > {map, unmap}_domain_page() to be usable. Those helpers are used to > map/unmap page tables while update Xen page-tables. > > Since commit 022387ee1a "xen/arm: mm: Don't open-code Xen PT update in > {set, clear}_fixmap()", setup_fixmap() will make use of the helpers > mentioned above. When booting Xen using GRUB, setup_fixmap() may be used > before map_domain_page() can be called. This will result to data abort: > > (XEN) Data Abort Trap. Syndrome=0x5 > (XEN) CPU0: Unexpected Trap: Data Abort > > [...] > > (XEN) Xen call trace: > (XEN) [<000000000025ab6c>] mm.c#xen_pt_update+0x2b4/0x59c (PC) > (XEN) [<000000000025ab20>] mm.c#xen_pt_update+0x268/0x59c (LR) > (XEN) [<000000000025ae70>] set_fixmap+0x1c/0x2c > (XEN) [<00000000002a9c98>] copy_from_paddr+0x7c/0xdc > (XEN) [<00000000002a4ae0>] has_xsm_magic+0x18/0x34 > (XEN) [<00000000002a5b5c>] bootfdt.c#early_scan_node+0x398/0x560 > (XEN) [<00000000002a5de0>] device_tree_for_each_node+0xbc/0x144 > (XEN) [<00000000002a5ed4>] boot_fdt_info+0x6c/0x260 > (XEN) [<00000000002ac0d0>] start_xen+0x108/0xc74 > (XEN) [<000000000020044c>] arm64/head.o#paging+0x60/0x88 > > During early boot, the page tables are either statically allocated in > Xen binary or allocated via alloc_boot_pages(). > > For statically allocated page-tables, they will already be mapped as > part of Xen binary. So we can easily find the virtual address. > > For dynamically allocated page-tables, we need to rely > map_domain_page() to be functionally working. > > For arm32, the call will be usable much before page can be dynamically > allocated (see setup_pagetables()). For arm64, the call will be usable > after setup_xenheap_mappings(). > > In both cases, memory are given to the boot allocator afterwards. So we > can rely on map_domain_page() for mapping page tables allocated > dynamically. > > The helpers xen_{map, unmap}_table() are now updated to take into > account the case where page-tables are part of Xen binary. > > Fixes: 022387ee1a ('xen/arm: mm: Don't open-code Xen PT update in {set, clear}_fixmap()') > Signed-off-by: Julien Grall <julien.grall@arm.com> > Release-acked-by: Juergen Gross <jgross@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > Changes in v3: > - Use is_xen_fixed_mfn > - Add a comment about demoting the type. > > Changes in v2: > - Add RaB Juergen > - Rework the check to avoid truncation > > Note this patch relies on is_xen_fixed_mfn to be correct (see [1]). > > [1] https://lists.xen.org/archives/html/xen-devel/2019-10/msg01138.html > --- > xen/arch/arm/mm.c | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c > index be23acfe26..4514bc6bb0 100644 > --- a/xen/arch/arm/mm.c > +++ b/xen/arch/arm/mm.c > @@ -964,11 +964,41 @@ static int create_xen_table(lpae_t *entry) > > static lpae_t *xen_map_table(mfn_t mfn) > { > + /* > + * We may require to map the page table before map_domain_page() is > + * useable. The requirements here is it must be useable as soon as > + * page-tables are allocated dynamically via alloc_boot_pages(). > + * > + * We need to do the check on physical address rather than virtual > + * address to avoid truncation on Arm32. Therefore is_kernel() cannot > + * be used. > + */ > + if ( system_state == SYS_STATE_early_boot ) > + { > + if ( is_xen_fixed_mfn(mfn) ) > + { > + /* > + * It is fine to demote the type because the size of Xen > + * will always fit in vaddr_t. > + */ > + vaddr_t offset = mfn_to_maddr(mfn) - virt_to_maddr(&_start); > + > + return (lpae_t *)(XEN_VIRT_START + offset); > + } > + } > + > return map_domain_page(mfn); > } > > static void xen_unmap_table(const lpae_t *table) > { > + /* > + * During early boot, xen_map_table() will not use map_domain_page() > + * for page-tables residing in Xen binary. So skip the unmap part. > + */ > + if ( system_state == SYS_STATE_early_boot && is_kernel(table) ) > + return; > + > unmap_domain_page(table); > } > > -- > 2.11.0 >
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index be23acfe26..4514bc6bb0 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -964,11 +964,41 @@ static int create_xen_table(lpae_t *entry) static lpae_t *xen_map_table(mfn_t mfn) { + /* + * We may require to map the page table before map_domain_page() is + * useable. The requirements here is it must be useable as soon as + * page-tables are allocated dynamically via alloc_boot_pages(). + * + * We need to do the check on physical address rather than virtual + * address to avoid truncation on Arm32. Therefore is_kernel() cannot + * be used. + */ + if ( system_state == SYS_STATE_early_boot ) + { + if ( is_xen_fixed_mfn(mfn) ) + { + /* + * It is fine to demote the type because the size of Xen + * will always fit in vaddr_t. + */ + vaddr_t offset = mfn_to_maddr(mfn) - virt_to_maddr(&_start); + + return (lpae_t *)(XEN_VIRT_START + offset); + } + } + return map_domain_page(mfn); } static void xen_unmap_table(const lpae_t *table) { + /* + * During early boot, xen_map_table() will not use map_domain_page() + * for page-tables residing in Xen binary. So skip the unmap part. + */ + if ( system_state == SYS_STATE_early_boot && is_kernel(table) ) + return; + unmap_domain_page(table); }
The current implementations of xen_{map, unmap}_table() expect {map, unmap}_domain_page() to be usable. Those helpers are used to map/unmap page tables while update Xen page-tables. Since commit 022387ee1a "xen/arm: mm: Don't open-code Xen PT update in {set, clear}_fixmap()", setup_fixmap() will make use of the helpers mentioned above. When booting Xen using GRUB, setup_fixmap() may be used before map_domain_page() can be called. This will result to data abort: (XEN) Data Abort Trap. Syndrome=0x5 (XEN) CPU0: Unexpected Trap: Data Abort [...] (XEN) Xen call trace: (XEN) [<000000000025ab6c>] mm.c#xen_pt_update+0x2b4/0x59c (PC) (XEN) [<000000000025ab20>] mm.c#xen_pt_update+0x268/0x59c (LR) (XEN) [<000000000025ae70>] set_fixmap+0x1c/0x2c (XEN) [<00000000002a9c98>] copy_from_paddr+0x7c/0xdc (XEN) [<00000000002a4ae0>] has_xsm_magic+0x18/0x34 (XEN) [<00000000002a5b5c>] bootfdt.c#early_scan_node+0x398/0x560 (XEN) [<00000000002a5de0>] device_tree_for_each_node+0xbc/0x144 (XEN) [<00000000002a5ed4>] boot_fdt_info+0x6c/0x260 (XEN) [<00000000002ac0d0>] start_xen+0x108/0xc74 (XEN) [<000000000020044c>] arm64/head.o#paging+0x60/0x88 During early boot, the page tables are either statically allocated in Xen binary or allocated via alloc_boot_pages(). For statically allocated page-tables, they will already be mapped as part of Xen binary. So we can easily find the virtual address. For dynamically allocated page-tables, we need to rely map_domain_page() to be functionally working. For arm32, the call will be usable much before page can be dynamically allocated (see setup_pagetables()). For arm64, the call will be usable after setup_xenheap_mappings(). In both cases, memory are given to the boot allocator afterwards. So we can rely on map_domain_page() for mapping page tables allocated dynamically. The helpers xen_{map, unmap}_table() are now updated to take into account the case where page-tables are part of Xen binary. Fixes: 022387ee1a ('xen/arm: mm: Don't open-code Xen PT update in {set, clear}_fixmap()') Signed-off-by: Julien Grall <julien.grall@arm.com> Release-acked-by: Juergen Gross <jgross@suse.com> --- Changes in v3: - Use is_xen_fixed_mfn - Add a comment about demoting the type. Changes in v2: - Add RaB Juergen - Rework the check to avoid truncation Note this patch relies on is_xen_fixed_mfn to be correct (see [1]). [1] https://lists.xen.org/archives/html/xen-devel/2019-10/msg01138.html --- xen/arch/arm/mm.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)