* [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
@ 2017-07-08 12:45 Benjamin Herrenschmidt
2017-07-10 3:51 ` Michael Ellerman
` (3 more replies)
0 siblings, 4 replies; 7+ messages in thread
From: Benjamin Herrenschmidt @ 2017-07-08 12:45 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Aneesh Kumar K.V, Michael Neuling
On radix, the process table entry we want to clear when
destroying a context is entry 0, not entry 1
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
arch/powerpc/mm/mmu_context_book3s64.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 79d8c8a..9404b5e 100644
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -226,9 +226,15 @@ void destroy_context(struct mm_struct *mm)
mm->context.cop_lockp = NULL;
#endif /* CONFIG_PPC_ICSWX */
- if (radix_enabled())
- process_tb[mm->context.id].prtb1 = 0;
- else
+ if (radix_enabled()) {
+ /*
+ * Radix doesn't have a valid bit in the process table
+ * entries. However we know that at least P9 implementation
+ * will avoid caching an entry with an invalid RTS field,
+ * and 0 is invalid. So this will do.
+ */
+ process_tb[mm->context.id].prtb0 = 0;
+ } else
subpage_prot_free(mm);
destroy_pagetable_page(mm);
__destroy_context(mm->context.id);
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-08 12:45 [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry Benjamin Herrenschmidt
@ 2017-07-10 3:51 ` Michael Ellerman
2017-07-10 3:59 ` Benjamin Herrenschmidt
2017-07-10 4:26 ` Nicholas Piggin
` (2 subsequent siblings)
3 siblings, 1 reply; 7+ messages in thread
From: Michael Ellerman @ 2017-07-10 3:51 UTC (permalink / raw)
To: Benjamin Herrenschmidt, linuxppc-dev; +Cc: Michael Neuling, Aneesh Kumar K.V
Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> On radix, the process table entry we want to clear when
> destroying a context is entry 0, not entry 1
.. but has no real world consequence? Or causes the system to instantly
catch fire?
I'll tag it:
Fixes: 7e381c0ff618 ("powerpc/mm/radix: Add mmu context handling callback for radix")
cheers
> diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
> index 79d8c8a..9404b5e 100644
> --- a/arch/powerpc/mm/mmu_context_book3s64.c
> +++ b/arch/powerpc/mm/mmu_context_book3s64.c
> @@ -226,9 +226,15 @@ void destroy_context(struct mm_struct *mm)
> mm->context.cop_lockp = NULL;
> #endif /* CONFIG_PPC_ICSWX */
>
> - if (radix_enabled())
> - process_tb[mm->context.id].prtb1 = 0;
> - else
> + if (radix_enabled()) {
> + /*
> + * Radix doesn't have a valid bit in the process table
> + * entries. However we know that at least P9 implementation
> + * will avoid caching an entry with an invalid RTS field,
> + * and 0 is invalid. So this will do.
> + */
> + process_tb[mm->context.id].prtb0 = 0;
> + } else
> subpage_prot_free(mm);
> destroy_pagetable_page(mm);
> __destroy_context(mm->context.id);
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-10 3:51 ` Michael Ellerman
@ 2017-07-10 3:59 ` Benjamin Herrenschmidt
2017-07-10 10:36 ` Michael Ellerman
0 siblings, 1 reply; 7+ messages in thread
From: Benjamin Herrenschmidt @ 2017-07-10 3:59 UTC (permalink / raw)
To: Michael Ellerman, linuxppc-dev; +Cc: Michael Neuling, Aneesh Kumar K.V
On Mon, 2017-07-10 at 13:51 +1000, Michael Ellerman wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
>
> > On radix, the process table entry we want to clear when
> > destroying a context is entry 0, not entry 1
>
> .. but has no real world consequence? Or causes the system to instantly
> catch fire?
It has no *immediate* consequence on P9 , but it can cause other bugs
to become worse (such as the KVM issue I'm chasing).
>
> I'll tag it:
>
> Fixes: 7e381c0ff618 ("powerpc/mm/radix: Add mmu context handling callback for radix")
>
> cheers
>
> > diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
> > index 79d8c8a..9404b5e 100644
> > --- a/arch/powerpc/mm/mmu_context_book3s64.c
> > +++ b/arch/powerpc/mm/mmu_context_book3s64.c
> > @@ -226,9 +226,15 @@ void destroy_context(struct mm_struct *mm)
> > mm->context.cop_lockp = NULL;
> > #endif /* CONFIG_PPC_ICSWX */
> >
> > - if (radix_enabled())
> > - process_tb[mm->context.id].prtb1 = 0;
> > - else
> > + if (radix_enabled()) {
> > + /*
> > + * Radix doesn't have a valid bit in the process table
> > + * entries. However we know that at least P9 implementation
> > + * will avoid caching an entry with an invalid RTS field,
> > + * and 0 is invalid. So this will do.
> > + */
> > + process_tb[mm->context.id].prtb0 = 0;
> > + } else
> > subpage_prot_free(mm);
> > destroy_pagetable_page(mm);
> > __destroy_context(mm->context.id);
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-08 12:45 [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry Benjamin Herrenschmidt
2017-07-10 3:51 ` Michael Ellerman
@ 2017-07-10 4:26 ` Nicholas Piggin
2017-07-10 5:15 ` Aneesh Kumar K.V
2017-07-11 12:48 ` [1/2] " Michael Ellerman
3 siblings, 0 replies; 7+ messages in thread
From: Nicholas Piggin @ 2017-07-10 4:26 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: linuxppc-dev, Michael Neuling, Aneesh Kumar K.V
On Sat, 08 Jul 2017 07:45:32 -0500
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> On radix, the process table entry we want to clear when
> destroying a context is entry 0, not entry 1
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This looks obviously correct to me.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-08 12:45 [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry Benjamin Herrenschmidt
2017-07-10 3:51 ` Michael Ellerman
2017-07-10 4:26 ` Nicholas Piggin
@ 2017-07-10 5:15 ` Aneesh Kumar K.V
2017-07-11 12:48 ` [1/2] " Michael Ellerman
3 siblings, 0 replies; 7+ messages in thread
From: Aneesh Kumar K.V @ 2017-07-10 5:15 UTC (permalink / raw)
To: Benjamin Herrenschmidt, linuxppc-dev; +Cc: Michael Neuling
Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> On radix, the process table entry we want to clear when
> destroying a context is entry 0, not entry 1
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/mmu_context_book3s64.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
> index 79d8c8a..9404b5e 100644
> --- a/arch/powerpc/mm/mmu_context_book3s64.c
> +++ b/arch/powerpc/mm/mmu_context_book3s64.c
> @@ -226,9 +226,15 @@ void destroy_context(struct mm_struct *mm)
> mm->context.cop_lockp = NULL;
> #endif /* CONFIG_PPC_ICSWX */
>
> - if (radix_enabled())
> - process_tb[mm->context.id].prtb1 = 0;
> - else
> + if (radix_enabled()) {
> + /*
> + * Radix doesn't have a valid bit in the process table
> + * entries. However we know that at least P9 implementation
> + * will avoid caching an entry with an invalid RTS field,
> + * and 0 is invalid. So this will do.
> + */
> + process_tb[mm->context.id].prtb0 = 0;
> + } else
> subpage_prot_free(mm);
> destroy_pagetable_page(mm);
> __destroy_context(mm->context.id);
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-10 3:59 ` Benjamin Herrenschmidt
@ 2017-07-10 10:36 ` Michael Ellerman
0 siblings, 0 replies; 7+ messages in thread
From: Michael Ellerman @ 2017-07-10 10:36 UTC (permalink / raw)
To: Benjamin Herrenschmidt, linuxppc-dev; +Cc: Michael Neuling, Aneesh Kumar K.V
Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> On Mon, 2017-07-10 at 13:51 +1000, Michael Ellerman wrote:
>> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
>>
>> > On radix, the process table entry we want to clear when
>> > destroying a context is entry 0, not entry 1
>>
>> .. but has no real world consequence? Or causes the system to instantly
>> catch fire?
>
> It has no *immediate* consequence on P9 , but it can cause other bugs
> to become worse (such as the KVM issue I'm chasing).
OK, I'll flag it for stable then to be safe.
cheers
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [1/2] powerpc/mm/radix: Properly clear process table entry
2017-07-08 12:45 [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry Benjamin Herrenschmidt
` (2 preceding siblings ...)
2017-07-10 5:15 ` Aneesh Kumar K.V
@ 2017-07-11 12:48 ` Michael Ellerman
3 siblings, 0 replies; 7+ messages in thread
From: Michael Ellerman @ 2017-07-11 12:48 UTC (permalink / raw)
To: Benjamin Herrenschmidt, linuxppc-dev; +Cc: Michael Neuling, Aneesh Kumar K.V
On Sat, 2017-07-08 at 12:45:32 UTC, Benjamin Herrenschmidt wrote:
> On radix, the process table entry we want to clear when
> destroying a context is entry 0, not entry 1
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/c6bb0b8d426a8cf865ca9c8a532cc3
cheers
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2017-07-11 12:48 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2017-07-08 12:45 [PATCH 1/2] powerpc/mm/radix: Properly clear process table entry Benjamin Herrenschmidt
2017-07-10 3:51 ` Michael Ellerman
2017-07-10 3:59 ` Benjamin Herrenschmidt
2017-07-10 10:36 ` Michael Ellerman
2017-07-10 4:26 ` Nicholas Piggin
2017-07-10 5:15 ` Aneesh Kumar K.V
2017-07-11 12:48 ` [1/2] " Michael Ellerman
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