On 11/10/22 00:48, Catalin Marinas wrote:
> On Thu, Oct 27, 2022 at 08:09:15AM +0530, Anshuman Khandual wrote:
>> +#define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
>> +static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
>> + unsigned long addr,
>> + pte_t *ptep)
>> +{
>> + pte_t pte = ptep_get_and_clear(vma->vm_mm, addr, ptep);
>>
>> + if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198)) {
>> + /*
>> + * Break-before-make (BBM) is required for all user space mappings
>> + * when the permission changes from executable to non-executable
>> + * in cases where cpu is affected with errata #2645198.
>> + */
>> + if (pte_user_exec(pte) && cpus_have_const_cap(ARM64_WORKAROUND_2645198))
>> + __flush_tlb_range(vma, addr, addr + PAGE_SIZE, PAGE_SIZE, false, 3);
>
> Why not flush_tlb_page() here?
>
> But more importantly, can we not use ptep_clear_flush() instead (and
Something like ...
ptep_modify_prot_start -
if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198)) {
if (pte_user_exec(READ_ONCE(*ptep)) && cpus_have_const_cap(ARM64_WORKAROUND_2645198))
return ptep_clear_flush(vma, addr, ptep);
} else {
return ptep_get_and_clear(vma->vm_mm, addr, ptep);
}
> huge_ptep_clear_flush())? They return the pte and do the TLBI.
huge_ptep_modify_prot_start -
if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198)) {
if (pte_user_exec(READ_ONCE(*ptep)) && cpus_have_const_cap(ARM64_WORKAROUND_2645198))
return huge_ptep_clear_flush(vma, addr, ptep);
} else {
return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
}
pte_user_exec(READ_ONCE(*ptep) should identify an user exec mapping even though
ptep represents a cont PTE/PMD huge page ? OR should huge_ptep_get() helper be
used instead ? Regardless, using [huge_]ptep_clear_flush() here seems better.
