* [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds()
@ 2022-04-24 6:33 Baolin Wang
2022-04-24 7:45 ` Muchun Song
0 siblings, 1 reply; 4+ messages in thread
From: Baolin Wang @ 2022-04-24 6:33 UTC (permalink / raw)
To: akpm, mike.kravetz
Cc: peterx, songmuchun, baolin.wang, linux-mm, linux-kernel
Missed calling flush_cache_range() before removing the sharing PMD entrires,
otherwise data consistence issue may be occurred on some architectures whose
caches are strict and require a virtual–>physical translation to exist for
a virtual address. Thus add it.
Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
mm/hugetlb.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 74c9964..1945dfb 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7058,6 +7058,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
if (start >= end)
return;
+ flush_cache_range(vma, start, end);
/*
* No need to call adjust_range_if_pmd_sharing_possible(), because
* we have already done the PUD_SIZE alignment.
--
1.8.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds()
2022-04-24 6:33 [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds() Baolin Wang
@ 2022-04-24 7:45 ` Muchun Song
2022-04-24 10:03 ` Baolin Wang
2022-04-26 17:34 ` Peter Xu
0 siblings, 2 replies; 4+ messages in thread
From: Muchun Song @ 2022-04-24 7:45 UTC (permalink / raw)
To: Baolin Wang; +Cc: akpm, mike.kravetz, peterx, linux-mm, linux-kernel
On Sun, Apr 24, 2022 at 02:33:19PM +0800, Baolin Wang wrote:
> Missed calling flush_cache_range() before removing the sharing PMD entrires,
> otherwise data consistence issue may be occurred on some architectures whose
> caches are strict and require a virtual–>physical translation to exist for
> a virtual address. Thus add it.
>
> Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
CONFIG_ARCH_WANT_HUGE_PMD_SHARE is only definded on riscv, arm64 and
x86. All of them do not have a VIVT cache. In others words,
flush_cache_range() is null on those architectures. So I suspect
in practice this does not cause any issue. It is better to
clarify this in commit log.
Anyway:
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds()
2022-04-24 7:45 ` Muchun Song
@ 2022-04-24 10:03 ` Baolin Wang
2022-04-26 17:34 ` Peter Xu
1 sibling, 0 replies; 4+ messages in thread
From: Baolin Wang @ 2022-04-24 10:03 UTC (permalink / raw)
To: Muchun Song; +Cc: akpm, mike.kravetz, peterx, linux-mm, linux-kernel
On 4/24/2022 3:45 PM, Muchun Song wrote:
> On Sun, Apr 24, 2022 at 02:33:19PM +0800, Baolin Wang wrote:
>> Missed calling flush_cache_range() before removing the sharing PMD entrires,
>> otherwise data consistence issue may be occurred on some architectures whose
>> caches are strict and require a virtual–>physical translation to exist for
>> a virtual address. Thus add it.
>>
>> Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>
> CONFIG_ARCH_WANT_HUGE_PMD_SHARE is only definded on riscv, arm64 and
> x86. All of them do not have a VIVT cache. In others words,
> flush_cache_range() is null on those architectures. So I suspect
> in practice this does not cause any issue. It is better to
> clarify this in commit log.
Yes, just from code inspection and to keep same behaviors when unmapping
sharing PMD entrires in case more architectures can support
CONFIG_ARCH_WANT_HUGE_PMD_SHARE in future. Will update the commit
message in next version.
>
> Anyway:
>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds()
2022-04-24 7:45 ` Muchun Song
2022-04-24 10:03 ` Baolin Wang
@ 2022-04-26 17:34 ` Peter Xu
1 sibling, 0 replies; 4+ messages in thread
From: Peter Xu @ 2022-04-26 17:34 UTC (permalink / raw)
To: Muchun Song; +Cc: Baolin Wang, akpm, mike.kravetz, linux-mm, linux-kernel
On Sun, Apr 24, 2022 at 03:45:02PM +0800, Muchun Song wrote:
> On Sun, Apr 24, 2022 at 02:33:19PM +0800, Baolin Wang wrote:
> > Missed calling flush_cache_range() before removing the sharing PMD entrires,
> > otherwise data consistence issue may be occurred on some architectures whose
> > caches are strict and require a virtual–>physical translation to exist for
> > a virtual address. Thus add it.
> >
> > Fixes: 6dfeaff93be1 ("hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp")
> > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>
> CONFIG_ARCH_WANT_HUGE_PMD_SHARE is only definded on riscv, arm64 and
> x86. All of them do not have a VIVT cache. In others words,
> flush_cache_range() is null on those architectures. So I suspect
> in practice this does not cause any issue. It is better to
> clarify this in commit log.
Looks correct.
>
> Anyway:
>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Thanks,
--
Peter Xu
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-04-24 6:33 [PATCH] mm: hugetlb: Add missing cache flushing in hugetlb_unshare_all_pmds() Baolin Wang
2022-04-24 7:45 ` Muchun Song
2022-04-24 10:03 ` Baolin Wang
2022-04-26 17:34 ` Peter Xu
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