* [PATCH] x86/mm/pti: remove dead logic during user pagetable population
@ 2018-01-06 17:50 Jike Song
2018-01-06 19:33 ` Thomas Gleixner
2018-01-06 20:03 ` Willy Tarreau
0 siblings, 2 replies; 7+ messages in thread
From: Jike Song @ 2018-01-06 17:50 UTC (permalink / raw)
To: tglx; +Cc: luto, linux-kernel, Jike Song
Signed-off-by: Jike Song <albcamus@gmail.com>
---
arch/x86/mm/pti.c | 28 ++++------------------------
1 file changed, 4 insertions(+), 24 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 43d4a4a29037..dc611d039bd5 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -164,12 +164,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (!new_p4d_page)
return NULL;
- if (pgd_none(*pgd)) {
- set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
- new_p4d_page = 0;
- }
- if (new_p4d_page)
- free_page(new_p4d_page);
+ set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
}
BUILD_BUG_ON(pgd_large(*pgd) != 0);
@@ -194,12 +189,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pud_page)
return NULL;
- if (p4d_none(*p4d)) {
- set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
- new_pud_page = 0;
- }
- if (new_pud_page)
- free_page(new_pud_page);
+ set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
}
pud = pud_offset(p4d, address);
@@ -213,12 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pmd_page)
return NULL;
- if (pud_none(*pud)) {
- set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
- new_pmd_page = 0;
- }
- if (new_pmd_page)
- free_page(new_pmd_page);
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
}
return pmd_offset(pud, address);
@@ -251,12 +236,7 @@ static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address)
if (!new_pte_page)
return NULL;
- if (pmd_none(*pmd)) {
- set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
- new_pte_page = 0;
- }
- if (new_pte_page)
- free_page(new_pte_page);
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
}
pte = pte_offset_kernel(pmd, address);
--
2.14.3
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-06 17:50 [PATCH] x86/mm/pti: remove dead logic during user pagetable population Jike Song
@ 2018-01-06 19:33 ` Thomas Gleixner
2018-01-07 3:00 ` Jike Song
2018-01-06 20:03 ` Willy Tarreau
1 sibling, 1 reply; 7+ messages in thread
From: Thomas Gleixner @ 2018-01-06 19:33 UTC (permalink / raw)
To: Jike Song; +Cc: luto, linux-kernel
On Sun, 7 Jan 2018, Jike Song wrote:
Care to explain why you think this is not needed?
Thanks,
tglx
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-06 19:33 ` Thomas Gleixner
@ 2018-01-07 3:00 ` Jike Song
2018-01-07 9:48 ` Thomas Gleixner
0 siblings, 1 reply; 7+ messages in thread
From: Jike Song @ 2018-01-07 3:00 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: luto, Linux Kernel Mailing List
On Sun, Jan 7, 2018 at 3:33 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Sun, 7 Jan 2018, Jike Song wrote:
>
> Care to explain why you think this is not needed?
>
Hi Thomas,
Look at one of the original code snippets:
162 if (pgd_none(*pgd)) {
163 unsigned long new_p4d_page = __get_free_page(gfp);
164 if (!new_p4d_page)
165 return NULL;
166
167 if (pgd_none(*pgd)) {
168 set_pgd(pgd, __pgd(_KERNPG_TABLE |
__pa(new_p4d_page)));
169 new_p4d_page = 0;
170 }
171 if (new_p4d_page)
172 free_page(new_p4d_page);
173 }
Correct me if I'm too dumb to see the rationale here, but to me there
can't be any difference between
two pgd_none(*pgd) of L162 and L167, so it is always false in L171.
> Thanks,
>
> tglx
--
Thanks,
Jike
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 3:00 ` Jike Song
@ 2018-01-07 9:48 ` Thomas Gleixner
2018-01-07 10:35 ` Jike Song
0 siblings, 1 reply; 7+ messages in thread
From: Thomas Gleixner @ 2018-01-07 9:48 UTC (permalink / raw)
To: Jike Song; +Cc: luto, Linux Kernel Mailing List
On Sun, 7 Jan 2018, Jike Song wrote:
> On Sun, Jan 7, 2018 at 3:33 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Sun, 7 Jan 2018, Jike Song wrote:
> >
> > Care to explain why you think this is not needed?
> >
>
> Hi Thomas,
>
> Look at one of the original code snippets:
>
> 162 if (pgd_none(*pgd)) {
> 163 unsigned long new_p4d_page = __get_free_page(gfp);
> 164 if (!new_p4d_page)
> 165 return NULL;
> 166
> 167 if (pgd_none(*pgd)) {
> 168 set_pgd(pgd, __pgd(_KERNPG_TABLE |
> __pa(new_p4d_page)));
> 169 new_p4d_page = 0;
> 170 }
> 171 if (new_p4d_page)
> 172 free_page(new_p4d_page);
> 173 }
>
> Correct me if I'm too dumb to see the rationale here, but to me there
> can't be any difference between
> two pgd_none(*pgd) of L162 and L167, so it is always false in L171.
Right, but this kind of explanation wants to be in the changelog. Empty
changelogs for this kind of change are just not acceptable.
Thanks,
tglx
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 9:48 ` Thomas Gleixner
@ 2018-01-07 10:35 ` Jike Song
0 siblings, 0 replies; 7+ messages in thread
From: Jike Song @ 2018-01-07 10:35 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: luto, Linux Kernel Mailing List
On Sun, Jan 7, 2018 at 5:48 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Sun, 7 Jan 2018, Jike Song wrote:
>> On Sun, Jan 7, 2018 at 3:33 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> > On Sun, 7 Jan 2018, Jike Song wrote:
>> >
>> > Care to explain why you think this is not needed?
>> >
>>
>> Hi Thomas,
>>
>> Look at one of the original code snippets:
>>
>> 162 if (pgd_none(*pgd)) {
>> 163 unsigned long new_p4d_page = __get_free_page(gfp);
>> 164 if (!new_p4d_page)
>> 165 return NULL;
>> 166
>> 167 if (pgd_none(*pgd)) {
>> 168 set_pgd(pgd, __pgd(_KERNPG_TABLE |
>> __pa(new_p4d_page)));
>> 169 new_p4d_page = 0;
>> 170 }
>> 171 if (new_p4d_page)
>> 172 free_page(new_p4d_page);
>> 173 }
>>
>> Correct me if I'm too dumb to see the rationale here, but to me there
>> can't be any difference between
>> two pgd_none(*pgd) of L162 and L167, so it is always false in L171.
>
> Right, but this kind of explanation wants to be in the changelog. Empty
> changelogs for this kind of change are just not acceptable.
>
Roger that, just sent v2 out :)
I'm not quite sure but I CCed stable@kernel.org anyway.
> Thanks,
>
> tglx
--
Thanks,
Jike
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-06 17:50 [PATCH] x86/mm/pti: remove dead logic during user pagetable population Jike Song
2018-01-06 19:33 ` Thomas Gleixner
@ 2018-01-06 20:03 ` Willy Tarreau
2018-01-07 3:05 ` Jike Song
1 sibling, 1 reply; 7+ messages in thread
From: Willy Tarreau @ 2018-01-06 20:03 UTC (permalink / raw)
To: Jike Song; +Cc: tglx, luto, linux-kernel
On Sun, Jan 07, 2018 at 01:50:59AM +0800, Jike Song wrote:
> Signed-off-by: Jike Song <albcamus@gmail.com>
It would be nice to have a commit message, particularly in this quite
sensitive series...
Willy
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/mm/pti: remove dead logic during user pagetable population
2018-01-06 20:03 ` Willy Tarreau
@ 2018-01-07 3:05 ` Jike Song
0 siblings, 0 replies; 7+ messages in thread
From: Jike Song @ 2018-01-07 3:05 UTC (permalink / raw)
To: Willy Tarreau; +Cc: Thomas Gleixner, luto, Linux Kernel Mailing List
On Sun, Jan 7, 2018 at 4:03 AM, Willy Tarreau <w@1wt.eu> wrote:
> On Sun, Jan 07, 2018 at 01:50:59AM +0800, Jike Song wrote:
>> Signed-off-by: Jike Song <albcamus@gmail.com>
>
> It would be nice to have a commit message, particularly in this quite
> sensitive series...
Yes that's useful, will add it in v2 :)
>
> Willy
--
Thanks,
Jike
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2018-01-07 10:35 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2018-01-06 17:50 [PATCH] x86/mm/pti: remove dead logic during user pagetable population Jike Song
2018-01-06 19:33 ` Thomas Gleixner
2018-01-07 3:00 ` Jike Song
2018-01-07 9:48 ` Thomas Gleixner
2018-01-07 10:35 ` Jike Song
2018-01-06 20:03 ` Willy Tarreau
2018-01-07 3:05 ` Jike Song
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