From a8bf2fc43fc63c0bd38b45c9a9616d43b683585d Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 23 Nov 2022 18:02:08 +0000 Subject: [PATCH] arm64/kpti: Move DAIF masking to C code We really don't want to take an exception while replacing TTBR1 so we mask DAIF during the actual update. Currently this is done in the assembly function idmap_cpu_replace_ttbr1() but it could equally be done in the only caller of that function, cpu_replace_ttbr1(). This simplifies the assembly code slightly and means that when working with the code around masking DAIF flags there is one less piece of assembly code which needs to be considered. While we're at it add a comment which makes explicit why we are masking DAIF in this code. There should be no functional effect. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20221123180209.634650-2-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/include/asm/mmu_context.h | 10 ++++++++++ arch/arm64/mm/proc.S | 4 ---- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index d3f8b5d..72dbd64 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -18,6 +18,7 @@ #include #include +#include #include #include #include @@ -152,6 +153,7 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap) typedef void (ttbr_replace_func)(phys_addr_t); extern ttbr_replace_func idmap_cpu_replace_ttbr1; ttbr_replace_func *replace_phys; + unsigned long daif; /* phys_to_ttbr() zeros lower 2 bits of ttbr with 52-bit PA */ phys_addr_t ttbr1 = phys_to_ttbr(virt_to_phys(pgdp)); @@ -171,7 +173,15 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap) replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1); __cpu_install_idmap(idmap); + + /* + * We really don't want to take *any* exceptions while TTBR1 is + * in the process of being replaced so mask everything. + */ + daif = local_daif_save(); replace_phys(ttbr1); + local_daif_restore(daif); + cpu_uninstall_idmap(); } diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index b9ecbba..066fa60 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -189,16 +189,12 @@ SYM_FUNC_END(cpu_do_resume) * called by anything else. It can only be executed from a TTBR0 mapping. */ SYM_TYPED_FUNC_START(idmap_cpu_replace_ttbr1) - save_and_disable_daif flags=x2 - __idmap_cpu_set_reserved_ttbr1 x1, x3 offset_ttbr1 x0, x3 msr ttbr1_el1, x0 isb - restore_daif x2 - ret SYM_FUNC_END(idmap_cpu_replace_ttbr1) .popsection -- 2.7.4