[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] arm/mmu: Move init_ttbr to a new section .data.idmap
commit 5ed59e62c6f28cbf855605e4e558aa556d2ea8f5 Author: Julien Grall <jgrall@xxxxxxxxxx> AuthorDate: Thu Jan 25 18:32:38 2024 +0000 Commit: Julien Grall <jgrall@xxxxxxxxxx> CommitDate: Thu Jan 25 18:36:51 2024 +0000 arm/mmu: Move init_ttbr to a new section .data.idmap With the upcoming work to color Xen, the binary will not be anymore physically contiguous. This will be a problem during boot as the assembly code will need to work out where each piece of Xen reside. An easy way to solve the issue is to have all code/data accessed by the secondary CPUs while the MMU is off within a single page. Right now, init_ttbr is used by secondary CPUs to find there page-tables before the MMU is on. Yet it is currently in .data which is unlikely to be within the same page as the rest of the idmap. Create a new section .data.idmap that will be used for variables accessed by the early boot code. The first one is init_ttbr. The idmap is currently part of the text section and therefore will be mapped read-only executable. This means that we need to temporarily remap init_ttbr in order to update it. Introduce a new function set_init_ttbr() for this purpose so the code is not duplicated between arm64 and arm32. Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx> --- xen/arch/arm/mmu/smpboot.c | 34 +++++++++++++++++++++++++++++----- xen/arch/arm/xen.lds.S | 1 + 2 files changed, 30 insertions(+), 5 deletions(-) diff --git a/xen/arch/arm/mmu/smpboot.c b/xen/arch/arm/mmu/smpboot.c index b6fc0aae07..bc91fdfe33 100644 --- a/xen/arch/arm/mmu/smpboot.c +++ b/xen/arch/arm/mmu/smpboot.c @@ -9,6 +9,10 @@ #include <asm/setup.h> +/* Override macros from asm/page.h to make them work with mfn_t */ +#undef virt_to_mfn +#define virt_to_mfn(va) _mfn(__virt_to_mfn(va)) + /* * Static start-of-day pagetables that we use before the allocators * are up. These are used by all CPUs during bringup before switching @@ -44,7 +48,7 @@ DEFINE_BOOT_PAGE_TABLE(boot_second); DEFINE_BOOT_PAGE_TABLES(boot_third, XEN_NR_ENTRIES(2)); /* Non-boot CPUs use this to find the correct pagetables. */ -uint64_t init_ttbr; +uint64_t __section(".data.idmap") init_ttbr; /* Clear a translation table and clean & invalidate the cache */ static void clear_table(void *table) @@ -68,6 +72,27 @@ static void clear_boot_pagetables(void) clear_table(boot_third); } +static void set_init_ttbr(lpae_t *root) +{ + /* + * init_ttbr is part of the identity mapping which is read-only. So + * we need to re-map the region so it can be updated. + */ + void *ptr = map_domain_page(virt_to_mfn(&init_ttbr)); + + ptr += PAGE_OFFSET(&init_ttbr); + + *(uint64_t *)ptr = virt_to_maddr(root); + + /* + * init_ttbr will be accessed with the MMU off, so ensure the update + * is visible by cleaning the cache. + */ + clean_dcache(ptr); + + unmap_domain_page(ptr); +} + #ifdef CONFIG_ARM_64 int prepare_secondary_mm(int cpu) { @@ -77,8 +102,8 @@ int prepare_secondary_mm(int cpu) * Set init_ttbr for this CPU coming up. All CPUs share a single setof * pagetables, but rewrite it each time for consistency with 32 bit. */ - init_ttbr = virt_to_maddr(xen_pgtable); - clean_dcache(init_ttbr); + set_init_ttbr(xen_pgtable); + return 0; } #else @@ -109,8 +134,7 @@ int prepare_secondary_mm(int cpu) clear_boot_pagetables(); /* Set init_ttbr for this CPU coming up */ - init_ttbr = __pa(first); - clean_dcache(init_ttbr); + set_init_ttbr(first); return 0; } diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S index 20598c6963..470c8f2208 100644 --- a/xen/arch/arm/xen.lds.S +++ b/xen/arch/arm/xen.lds.S @@ -36,6 +36,7 @@ SECTIONS *(.text.header) *(.text.idmap) *(.rodata.idmap) + *(.data.idmap) _idmap_end = .; *(.text.cold) -- generated by git-patchbot for /home/xen/git/xen.git#master
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