| Message ID | 1499517932.3397.22.camel@kernel.crashing.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c6bb0b8d426a8cf865ca9c8a532cc3a2927cfceb |
| Headers | show |
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);
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);
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.
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);
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
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
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);
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(-)