Xen project Mailing List

[xen master] xen/arm32: head: Widen the use of the temporary mapping

Date: Sun, 30 Jul 2023 06:17:06 +0000

Delivery-date: Sun, 30 Jul 2023 06:17:07 +0000

List-id: "Change log for Mercurial \(receive only\)" <xen-changelog.lists.xenproject.org>

commit 5e213f0f4d2ca4f286f8423316ed8090bcc5fef8 Author: Julien Grall <jgrall@xxxxxxxxxx> AuthorDate: Mon Jul 24 11:14:58 2023 +0100 Commit: Julien Grall <julien@xxxxxxx> CommitDate: Thu Jul 27 23:05:53 2023 +0100 xen/arm32: head: Widen the use of the temporary mapping 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 <jgrall@xxxxxxxxxx> ---- This patch was originally part of [1] but it was reverted due to Xen not booting on the Arndale. The second patch of this series is fixing it (confirmed by booting on the Arndale). So I am including this patch. [1] https://lore.kernel.org/xen-devel/20230416143211.72227-1-julien@xxxxxxx/ Changes in new v2: - Rebase - Drop reviewed-by tags 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 Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx> Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx> Tested-by: Luca Fancellu <luca.fancellu@xxxxxxx> --- 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 26fc420b2e..33b038e7e0 100644 --- a/xen/arch/arm/arm32/head.S +++ b/xen/arch/arm/arm32/head.S @@ -473,7 +473,6 @@ 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 /* * We need to use a stash register because @@ -519,70 +518,37 @@ create_page_tables: cmp r1, r0 /* Loop until we map all of Xen */ 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 @@ -720,33 +686,13 @@ 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) -- generated by git-patchbot for /home/xen/git/xen.git#master

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