Re: [PATCH V2] riscv: Fixup race condition on PG_dcache_clean in flush_icache_pte

[Guo Ren]

On Sat, Jan 28, 2023 at 7:36 AM Conor Dooley <conor@xxxxxxxxxx> wrote:
>
> Hey Guo Ren,
>
> On Thu, Jan 26, 2023 at 10:53:06PM -0500, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > In commit 588a513d3425 ("arm64: Fix race condition on PG_dcache_clean
> > in __sync_icache_dcache()"), we found RISC-V has the same issue as the
> > previous arm64. The previous implementation didn't guarantee the correct
> > sequence of operations, which means flush_icache_all() hasn't been
> > called when the PG_dcache_clean was set. That would cause a risk of page
> > synchronization.
> >
> > Fixes: 08f051eda33b ("RISC-V: Flush I$ when making a dirty page executable")
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > ---
> > Changelog:
> > V2:
> >  - Optimize commit log
>
> Probably would have benefited from providing the analysis that the arm64
> commit did, for riscv, rather than referring to theirs.
Maybe you are right, but they are almost the same for this patch. So I
didn't want to duplicate the commit log but gave out the original
instead.

> But that's not really important and the diff itself seems sound, so:
> Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Thx.

>
> Thanks,
> Conor.
>
> >  - Rebase on riscv for-next (20230127)
> >
> > V1:
> > https://lore.kernel.org/linux-riscv/20221023133205.3493564-2-guoren@xxxxxxxxxx/
> > ---
> >  arch/riscv/mm/cacheflush.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> > index 3cc07ed45aeb..fcd6145fbead 100644
> > --- a/arch/riscv/mm/cacheflush.c
> > +++ b/arch/riscv/mm/cacheflush.c
> > @@ -90,8 +90,10 @@ void flush_icache_pte(pte_t pte)
> >       if (PageHuge(page))
> >               page = compound_head(page);
> >
> > -     if (!test_and_set_bit(PG_dcache_clean, &page->flags))
> > +     if (!test_bit(PG_dcache_clean, &page->flags)) {
> >               flush_icache_all();
> > +             set_bit(PG_dcache_clean, &page->flags);
> > +     }
> >  }
> >  #endif /* CONFIG_MMU */
> >
> > --
> > 2.36.1
> >



-- 
Best Regards
 Guo Ren