Messages in this thread Patch in this message | | | From | Alistair Francis <> | Subject | [PATCH] riscv: Ensure only ASIDLEN is used for sfence.vma | Date | Wed, 30 Mar 2022 17:33:47 +1000 |
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From: Alistair Francis <alistair.francis@wdc.com>
When we set the value of context.id using __new_context() we set both the asid and the current_version with this return statement in __new_context():
return asid | ver;
This means that when local_flush_tlb_all_asid() is called with the asid specified from context.id we can write the incorrect value.
We get away with this as hardware ignores the extra bits, as the RISC-V specification states:
"bits SXLEN-1:ASIDMAX of the value held in rs2 are reserved for future standard use. Until their use is defined by a standard extension, they should be zeroed by software and ignored by current implementations."
but it is still a bug and worth addressing as we are incorrectly setting extra bits.
This patch uses asid_mask when calling sfence.vma to ensure the asid is always the correct len (ASIDLEN). This is similar to what we do in arch/riscv/mm/context.c.
Signed-off-by: Alistair Francis <alistair.francis@wdc.com> --- arch/riscv/mm/context.c | 2 +- arch/riscv/mm/tlbflush.c | 4 ++-- include/linux/mm_types.h | 2 ++ 3 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c index 7acbfbd14557..4329fe54176b 100644 --- a/arch/riscv/mm/context.c +++ b/arch/riscv/mm/context.c @@ -22,7 +22,7 @@ DEFINE_STATIC_KEY_FALSE(use_asid_allocator); static unsigned long asid_bits; static unsigned long num_asids; -static unsigned long asid_mask; +unsigned long asid_mask; static atomic_long_t current_version; diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c index 37ed760d007c..4469615aa07f 100644 --- a/arch/riscv/mm/tlbflush.c +++ b/arch/riscv/mm/tlbflush.c @@ -10,7 +10,7 @@ static inline void local_flush_tlb_all_asid(unsigned long asid) { __asm__ __volatile__ ("sfence.vma x0, %0" : - : "r" (asid) + : "r" (asid & asid_mask) : "memory"); } @@ -19,7 +19,7 @@ static inline void local_flush_tlb_page_asid(unsigned long addr, { __asm__ __volatile__ ("sfence.vma %0, %1" : - : "r" (addr), "r" (asid) + : "r" (addr), "r" (asid & asid_mask) : "memory"); } diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 8834e38c06a4..5fa7cc0af853 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -666,6 +666,8 @@ struct mm_struct { extern struct mm_struct init_mm; +extern unsigned long asid_mask; + /* Pointer magic because the dynamic array size confuses some compilers. */ static inline void mm_init_cpumask(struct mm_struct *mm) { -- 2.35.1
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