On Thu, Nov 10, 2022 at 08:45:07AM +0530, Anshuman Khandual wrote:
On 11/10/22 00:48, Catalin Marinas wrote:
quoted
On Thu, Oct 27, 2022 at 08:09:15AM +0530, Anshuman Khandual wrote:
quoted
+#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);
}
Yes, this should work but avoid the 'else' when you have a return, so
something like:
if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198) &&
cpus_have_const_cap(ARM64_WORKAROUND_2645198) &&
pte_user_exec(READ_ONCE(*ptep)))
return ptep_clear_flush(vma, addr, ptep);
return ptep_get_and_clear(vma->vm_mm, addr, ptep);
quoted
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 ?
This should work as a shortcut. The contiguous ptes should all be the
same, so it's sufficient to check one of them.
--
Catalin
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