[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 4/5] xen: arm: avoid unnecessary aliasing in boot page tables.
If the identity map is created at one level then avoid creating entries further down the boot page tables, since these will be aliases at strange virtual address i.e. if the load address is such that both first_table_offset and second_table_offset are non-zero then we should avoid creating a mapping in boot_second, because the proper mapping is already in boot_first. We still do not handle the case where the load address is within the 2MB range starting at XEN_VIRT_START. This is not a regression but this patch tries to provide a more useful diagnostic message. Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> --- xen/arch/arm/arm32/head.S | 14 +++++++++++++- xen/arch/arm/arm64/head.S | 14 +++++++++++++- 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S index 3a72195..348ca7d 100644 --- a/xen/arch/arm/arm32/head.S +++ b/xen/arch/arm/arm32/head.S @@ -45,7 +45,7 @@ * r3 - * r4 - * r5 - - * r6 - + * r6 - identity map in place * r7 - CPUID * r8 - DTB address (boot CPU only) * r9 - paddr(start) @@ -250,6 +250,8 @@ cpu_init_done: * mapping. So each CPU must rebuild the page tables here with * the 1:1 in place. */ + mov r6, #0 /* r6 := identity map not yet in place */ + /* Write Xen's PT's paddr into the HTTBR */ ldr r4, =boot_pgtable add r4, r4, r10 /* r4 := paddr (boot_pagetable) */ @@ -275,6 +277,7 @@ cpu_init_done: orr r2, r2, #PT_LOWER(MEM) lsl r1, r1, #3 /* r1 := Slot offset */ strd r2, r3, [r4, r1] /* Mapping of paddr(start) */ + mov r6, #1 /* r6 := identity map now in place */ 1: /* Setup boot_second: */ ldr r4, =boot_second @@ -290,6 +293,8 @@ cpu_init_done: strd r2, r3, [r4, #8] /* Map it in slot 1 */ /* ... map of paddr(start) in boot_second */ + cmp r6, #1 /* r6 is set if already created */ + beq 1f lsrs r1, r9, #SECOND_SHIFT /* Offset of base paddr in boot_second */ mov r2, #0x0ff /* r2 := LPAE entries mask */ orr r2, r2, #0x100 @@ -307,6 +312,7 @@ cpu_init_done: orr r2, r2, #PT_LOWER(MEM) lsl r1, r1, #3 /* r1 := Slot offset */ strd r2, r3, [r4, r1] /* Mapping of paddr(start) */ + mov r6, #1 /* r6 := identity map now in place */ /* Setup boot_third: */ 1: ldr r4, =boot_third @@ -330,6 +336,12 @@ cpu_init_done: /* boot pagetable setup complete */ + cmp r6, #1 /* Did we manage to create an identity mapping ? */ + beq 1f + PRINT("Unable to build boot page tables - Failed to identity map Xen.\r\n") + b fail + +1: PRINT("- Turning on paging -\r\n") ldr r1, =paging /* Explicit vaddr, not RIP-relative */ diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index 023a9b9..7152d9c 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -62,7 +62,7 @@ * x22 - is_secondary_cpu * x23 - UART address * x24 - cpuid - * x25 - + * x25 - identity map in place * x26 - * x27 - * x28 - @@ -253,6 +253,8 @@ skip_bss: * mapping. So each CPU must rebuild the page tables here with * the 1:1 in place. */ + mov x25, #0 /* x25 := identity map not yet in place */ + /* Write Xen's PT's paddr into TTBR0_EL2 */ ldr x4, =boot_pgtable add x4, x4, x20 /* x4 := paddr (boot_pagetable) */ @@ -293,6 +295,7 @@ skip_bss: lsl x1, x1, #3 /* x1 := Slot offset */ str x2, [x4, x1] /* Mapping of paddr(start)*/ + mov x25, #1 /* x25 := identity map now in place */ 1: /* Setup boot_first: */ ldr x4, =boot_first /* Next level into boot_first */ @@ -306,6 +309,7 @@ skip_bss: str x2, [x4, #0] /* Map it in slot 0 */ /* ... map of paddr(start) in boot_first */ + cbnz x25, 1f /* x25 is set if already created */ lsr x2, x19, #FIRST_SHIFT /* x2 := Offset of base paddr in boot_first */ and x1, x2, 0x1ff /* x1 := Slot to use */ cbz x1, 1f /* It's in slot 0, map in boot_second */ @@ -315,6 +319,7 @@ skip_bss: orr x2, x2, x3 lsl x1, x1, #3 /* x1 := Slot offset */ str x2, [x4, x1] /* Create mapping of paddr(start)*/ + mov x25, #1 /* x25 := identity map now in place */ 1: /* Setup boot_second: */ ldr x4, =boot_second /* Next level into boot_second */ @@ -328,6 +333,7 @@ skip_bss: str x2, [x4, #8] /* Map it in slot 1 */ /* ... map of paddr(start) in boot_second */ + cbnz x25, 1f /* x25 is set if already created */ lsr x2, x19, #SECOND_SHIFT /* x2 := Offset of base paddr in boot_second */ and x1, x2, 0x1ff /* x1 := Slot to use */ cmp x1, #1 @@ -343,6 +349,7 @@ skip_bss: orr x2, x2, x3 lsl x1, x1, #3 /* x1 := Slot offset */ str x2, [x4, x1] /* Create mapping of paddr(start)*/ + mov x25, #1 /* x25 := identity map now in place */ 1: /* Setup boot_third: */ ldr x4, =boot_third @@ -366,6 +373,11 @@ skip_bss: /* boot pagetable setup complete */ + cbnz x25, 1f /* Did we manage to create an identity mapping ? */ + PRINT("Unable to build boot page tables - Failed to identity map Xen.\r\n") + b fail + +1: PRINT("- Turning on paging -\r\n") ldr x1, =paging /* Explicit vaddr, not RIP-relative */ -- 1.7.10.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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