Messages in this thread | | | From | Yu Zhao <> | Date | Thu, 24 Nov 2022 14:26:36 -0700 | Subject | Re: [PATCH v2] mm: introduce arch_has_hw_nonleaf_pmd_young() |
| |
On Thu, Nov 24, 2022 at 7:30 AM Juergen Gross <jgross@suse.com> wrote: > > Hi, > > On 24.11.22 15:08, Geert Uytterhoeven wrote: > > Hi Jürgen, > > > > On Wed, Nov 23, 2022 at 7:53 AM Juergen Gross <jgross@suse.com> wrote: > >> When running as a Xen PV guests commit eed9a328aa1a ("mm: x86: add > >> CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG") can cause a protection violation > >> in pmdp_test_and_clear_young(): > >> > >> BUG: unable to handle page fault for address: ffff8880083374d0 > >> #PF: supervisor write access in kernel mode > >> #PF: error_code(0x0003) - permissions violation > >> PGD 3026067 P4D 3026067 PUD 3027067 PMD 7fee5067 PTE 8010000008337065 > >> Oops: 0003 [#1] PREEMPT SMP NOPTI > >> CPU: 7 PID: 158 Comm: kswapd0 Not tainted 6.1.0-rc5-20221118-doflr+ #1 > >> RIP: e030:pmdp_test_and_clear_young+0x25/0x40 > >> > >> This happens because the Xen hypervisor can't emulate direct writes to > >> page table entries other than PTEs. > >> > >> This can easily be fixed by introducing arch_has_hw_nonleaf_pmd_young() > >> similar to arch_has_hw_pte_young() and test that instead of > >> CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG. > >> > >> Fixes: eed9a328aa1a ("mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG") > >> Reported-by: Sander Eikelenboom <linux@eikelenboom.it> > >> Signed-off-by: Juergen Gross <jgross@suse.com> > >> Acked-by: Yu Zhao <yuzhao@google.com> > >> Tested-by: Sander Eikelenboom <linux@eikelenboom.it> > >> --- > >> V2: > >> - correct function name in commit message to match patch > > > > Thanks for your patch, which is now commit 3f85e711d5af4fb4 ("mm: > > introduce arch_has_hw_nonleaf_pmd_young()") in next-20221124. > > > > noreply@ellerman.id.au reported a build failure for m68k/allmodconfig, > > which I have bisected to this commit. > > > >> --- a/mm/vmscan.c > >> +++ b/mm/vmscan.c > > > >> @@ -4073,14 +4073,14 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, > >> #endif > >> walk->mm_stats[MM_NONLEAF_TOTAL]++; > >> > >> -#ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG > >> - if (get_cap(LRU_GEN_NONLEAF_YOUNG)) { > >> + if (arch_has_hw_nonleaf_pmd_young() && > >> + get_cap(LRU_GEN_NONLEAF_YOUNG)) { > >> if (!pmd_young(val)) > > > > mm/vmscan.c:4102:30: error: implicit declaration of function > > 'pmd_young'; did you mean 'pte_young'? > > [-Werror=implicit-function-declaration] > > > > pmd_young() seems to be defined only on a handful of architectures. > > What would be the preferred fix for that? > > I could offer: > > - use V1 of the patch > - add the #ifdefs again to this patch (which would be kind of weird) > - use the attached patch
Your patch looks good to me:
Acked-by: Yu Zhao <yuzhao@google.com>
Thanks.
| |