Hi Julien, > On 19 Jun 2023, at 19:01, Julien Grall <jul...@xen.org> wrote: > > From: Julien Grall <jgr...@amazon.com> > > At the moment, the temporary mapping is only used when the virtual > runtime region of Xen is clashing with the physical region. > > In follow-up patches, we will rework how secondary CPU bring-up works > and it will be convenient to use the fixmap area for accessing > the root page-table (it is per-cpu). > > Rework the code to use temporary mapping when the Xen physical address > is not overlapping with the temporary mapping. > > This also has the advantage to simplify the logic to identity map > Xen. > > Signed-off-by: Julien Grall <jgr...@amazon.com> > Reviewed-by: Henry Wang <henry.w...@arm.com> > Reviewed-by: Michal Orzel <michal.or...@amd.com>
Acked-by: Bertrand Marquis <bertrand.marq...@arm.com> Cheers Bertrand > > ---- > > This patch was originally part of [1] but it was reverted due to > Xen not booting on the Arndale. The first patch of this series > is fixing it (confirmed by booting on the Arndale). So I am including > this patch. Also all the tags but the tested-by have been kept > because the code has not changed. Happy to drop any if there are > any concerns. > > [1] https://lore.kernel.org/xen-devel/20230416143211.72227-1-jul...@xen.org/ > > Changelog from the previous series: > > Changes in v6: > - Add Henry's reviewed-by and tested-by tag > - Add Michal's reviewed-by > - Add newline in remove_identity_mapping for clarity > > Changes in v5: > - Fix typo in a comment > - No need to link boot_{second, third}_id again if we need to > create a temporary area. > > Changes in v3: > - Resolve conflicts after switching from "ldr rX, <label>" to > "mov_w rX, <label>" in a previous patch > > Changes in v2: > - Patch added > --- > xen/arch/arm/arm32/head.S | 86 ++++++++------------------------------- > 1 file changed, 16 insertions(+), 70 deletions(-) > > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S > index b942e7e54d08..d70e856ab7dd 100644 > --- a/xen/arch/arm/arm32/head.S > +++ b/xen/arch/arm/arm32/head.S > @@ -459,7 +459,6 @@ ENDPROC(cpu_init) > create_page_tables: > /* Prepare the page-tables for mapping Xen */ > mov_w r0, XEN_VIRT_START > - create_table_entry boot_pgtable, boot_second, r0, 1 > create_table_entry boot_second, boot_third, r0, 2 > > /* Setup boot_third: */ > @@ -479,70 +478,37 @@ create_page_tables: > cmp r1, #(XEN_PT_LPAE_ENTRIES<<3) /* 512*8-byte entries per page */ > blo 1b > > - /* > - * If Xen is loaded at exactly XEN_VIRT_START then we don't > - * need an additional 1:1 mapping, the virtual mapping will > - * suffice. > - */ > - cmp r9, #XEN_VIRT_START > - moveq pc, lr > - > /* > * Setup the 1:1 mapping so we can turn the MMU on. Note that > * only the first page of Xen will be part of the 1:1 mapping. > - * > - * In all the cases, we will link boot_third_id. So create the > - * mapping in advance. > */ > + create_table_entry boot_pgtable, boot_second_id, r9, 1 > + create_table_entry boot_second_id, boot_third_id, r9, 2 > create_mapping_entry boot_third_id, r9, r9 > > /* > - * Find the first slot used. If the slot is not XEN_FIRST_SLOT, > - * then the 1:1 mapping will use its own set of page-tables from > - * the second level. > + * Find the first slot used. If the slot is not the same > + * as TEMPORARY_AREA_FIRST_SLOT, then we will want to switch > + * to the temporary mapping before jumping to the runtime > + * virtual mapping. > */ > get_table_slot r1, r9, 1 /* r1 := first slot */ > - cmp r1, #XEN_FIRST_SLOT > - beq 1f > - create_table_entry boot_pgtable, boot_second_id, r9, 1 > - b link_from_second_id > - > -1: > - /* > - * Find the second slot used. If the slot is XEN_SECOND_SLOT, then > the > - * 1:1 mapping will use its own set of page-tables from the > - * third level. > - */ > - get_table_slot r1, r9, 2 /* r1 := second slot */ > - cmp r1, #XEN_SECOND_SLOT > - beq virtphys_clash > - create_table_entry boot_second, boot_third_id, r9, 2 > - b link_from_third_id > + cmp r1, #TEMPORARY_AREA_FIRST_SLOT > + bne use_temporary_mapping > > -link_from_second_id: > - create_table_entry boot_second_id, boot_third_id, r9, 2 > -link_from_third_id: > - /* Good news, we are not clashing with Xen virtual mapping */ > + mov_w r0, XEN_VIRT_START > + create_table_entry boot_pgtable, boot_second, r0, 1 > mov r12, #0 /* r12 := temporary mapping not created > */ > mov pc, lr > > -virtphys_clash: > +use_temporary_mapping: > /* > - * The identity map clashes with boot_third. Link boot_first_id and > - * map Xen to a temporary mapping. See switch_to_runtime_mapping > - * for more details. > + * The identity mapping is not using the first slot > + * TEMPORARY_AREA_FIRST_SLOT. Create a temporary mapping. > + * See switch_to_runtime_mapping for more details. > */ > - PRINT("- Virt and Phys addresses clash -\r\n") > PRINT("- Create temporary mapping -\r\n") > > - /* > - * This will override the link to boot_second in XEN_FIRST_SLOT. > - * The page-tables are not live yet. So no need to use > - * break-before-make. > - */ > - create_table_entry boot_pgtable, boot_second_id, r9, 1 > - create_table_entry boot_second_id, boot_third_id, r9, 2 > - > /* Map boot_second (cover Xen mappings) to the temporary 1st slot */ > mov_w r0, TEMPORARY_XEN_VIRT_START > create_table_entry boot_pgtable, boot_second, r0, 1 > @@ -680,33 +646,13 @@ remove_identity_mapping: > /* r2:r3 := invalid page-table entry */ > mov r2, #0x0 > mov r3, #0x0 > - /* > - * Find the first slot used. Remove the entry for the first > - * table if the slot is not XEN_FIRST_SLOT. > - */ > + > + /* Find the first slot used and remove it */ > get_table_slot r1, r9, 1 /* r1 := first slot */ > - cmp r1, #XEN_FIRST_SLOT > - beq 1f > - /* It is not in slot 0, remove the entry */ > mov_w r0, boot_pgtable /* r0 := root table */ > lsl r1, r1, #3 /* r1 := Slot offset */ > strd r2, r3, [r0, r1] > - b identity_mapping_removed > - > -1: > - /* > - * Find the second slot used. Remove the entry for the first > - * table if the slot is not XEN_SECOND_SLOT. > - */ > - get_table_slot r1, r9, 2 /* r1 := second slot */ > - cmp r1, #XEN_SECOND_SLOT > - beq identity_mapping_removed > - /* It is not in slot 1, remove the entry */ > - mov_w r0, boot_second /* r0 := second table */ > - lsl r1, r1, #3 /* r1 := Slot offset */ > - strd r2, r3, [r0, r1] > > -identity_mapping_removed: > flush_xen_tlb_local r0 > mov pc, lr > ENDPROC(remove_identity_mapping) > -- > 2.40.1 >
