Hello, Dave Hansen Could you help review the patches, please?
I think they meet your suggestion except for forcing alignment in the caller. The reason is in the code. Thanks Lai On Thu, Dec 10, 2020 at 9:34 PM Lai Jiangshan <[email protected]> wrote: > > From: Lai Jiangshan <[email protected]> > > The commit 825d0b73cd752("x86/mm/pti: Handle unaligned address gracefully > in pti_clone_pagetable()") handles unaligned address well for unmapped > PUD/PMD etc. But unaligned address for mapped pmd also needs to > be aware. > > For mapped pmd, if @addr is not aligned to PMD_SIZE, the next pmd > (PTI_CLONE_PMD or the next pmd is large) or the last ptes (PTI_CLONE_PTE) > in the next pmd will not be cloned when @end < @addr + PMD_SIZE in the > current logic in the code. > > It is not a good idea to force alignment in the caller due to one of > the cases (see the comments in the code), so it just handles the alignment > in pti_clone_pagetable(). > > Signed-off-by: Lai Jiangshan <[email protected]> > --- > arch/x86/mm/pti.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c > index 1aab92930569..7ee99ef13a99 100644 > --- a/arch/x86/mm/pti.c > +++ b/arch/x86/mm/pti.c > @@ -342,6 +342,21 @@ pti_clone_pgtable(unsigned long start, unsigned long end, > } > > if (pmd_large(*pmd) || level == PTI_CLONE_PMD) { > + /* > + * pti_clone_kernel_text() might be called with > + * @start not aligned to PMD_SIZE. We need to make > + * it aligned, otherwise the next pmd or last ptes > + * are not cloned when @end < @addr + PMD_SIZE. > + * > + * We can't force pti_clone_kernel_text() to align > + * the @addr to PMD_SIZE when level == PTI_CLONE_PTE. > + * But the problem can still possible exist when the > + * first pmd is large. And it is not a good idea to > + * check whether the first pmd is large or not in the > + * caller, so we just simply align it here. > + */ > + addr = round_down(addr, PMD_SIZE); > + > target_pmd = pti_user_pagetable_walk_pmd(addr); > if (WARN_ON(!target_pmd)) > return; > -- > 2.19.1.6.gb485710b >
