From: Mike Rapoport <rppt@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-mm@kvack.org, Paul Mackerras <paulus@samba.org>,
Pavel Machek <pavel@ucw.cz>, "H. Peter Anvin" <hpa@zytor.com>,
sparclinux@vger.kernel.org, Christoph Lameter <cl@linux.com>,
Will Deacon <will@kernel.org>,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
Michael Ellerman <mpe@ellerman.id.au>,
x86@kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Ingo Molnar <mingo@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Len Brown <len.brown@intel.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Vasily Gorbik <gor@linux.ibm.com>,
linux-pm@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
David Rientjes <rientjes@google.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Thomas Gleixner <tglx@linutronix.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-arm-kernel@lists.infradead.org,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-kernel@vger.kernel.org, Pekka Enberg <penberg@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
linuxppc-dev@lists.ozlabs.org,
"David S. Miller" <davem@davemloft.net>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v4 3/4] arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC
Date: Thu, 5 Nov 2020 13:42:00 +0200 [thread overview]
Message-ID: <20201105114200.GZ4879@kernel.org> (raw)
In-Reply-To: <f9c1dc66-fc60-db4d-9670-0271adb2ed07@suse.cz>
On Wed, Nov 04, 2020 at 07:02:20PM +0100, Vlastimil Babka wrote:
> On 11/3/20 5:20 PM, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@linux.ibm.com>
>
> Subject should have "on DEBUG_PAGEALLOC" ?
>
> > The design of DEBUG_PAGEALLOC presumes that __kernel_map_pages() must never
> > fail. With this assumption is wouldn't be safe to allow general usage of
> > this function.
> >
> > Moreover, some architectures that implement __kernel_map_pages() have this
> > function guarded by #ifdef DEBUG_PAGEALLOC and some refuse to map/unmap
> > pages when page allocation debugging is disabled at runtime.
> >
> > As all the users of __kernel_map_pages() were converted to use
> > debug_pagealloc_map_pages() it is safe to make it available only when
> > DEBUG_PAGEALLOC is set.
> >
> > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> > Acked-by: David Hildenbrand <david@redhat.com>
> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> > arch/Kconfig | 3 +++
> > arch/arm64/Kconfig | 4 +---
> > arch/arm64/mm/pageattr.c | 8 ++++++--
> > arch/powerpc/Kconfig | 5 +----
> > arch/riscv/Kconfig | 4 +---
> > arch/riscv/include/asm/pgtable.h | 2 --
> > arch/riscv/mm/pageattr.c | 2 ++
> > arch/s390/Kconfig | 4 +---
> > arch/sparc/Kconfig | 4 +---
> > arch/x86/Kconfig | 4 +---
> > arch/x86/mm/pat/set_memory.c | 2 ++
> > include/linux/mm.h | 10 +++++++---
> > 12 files changed, 26 insertions(+), 26 deletions(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 56b6ccc0e32d..56d4752b6db6 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -1028,6 +1028,9 @@ config HAVE_STATIC_CALL_INLINE
> > bool
> > depends on HAVE_STATIC_CALL
> > +config ARCH_SUPPORTS_DEBUG_PAGEALLOC
> > + bool
> > +
> > source "kernel/gcov/Kconfig"
> > source "scripts/gcc-plugins/Kconfig"
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 1d466addb078..a932810cfd90 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -71,6 +71,7 @@ config ARM64
> > select ARCH_USE_QUEUED_RWLOCKS
> > select ARCH_USE_QUEUED_SPINLOCKS
> > select ARCH_USE_SYM_ANNOTATIONS
> > + select ARCH_SUPPORTS_DEBUG_PAGEALLOC
> > select ARCH_SUPPORTS_MEMORY_FAILURE
> > select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
> > select ARCH_SUPPORTS_ATOMIC_RMW
> > @@ -1025,9 +1026,6 @@ config HOLES_IN_ZONE
> > source "kernel/Kconfig.hz"
> > -config ARCH_SUPPORTS_DEBUG_PAGEALLOC
> > - def_bool y
> > -
> > config ARCH_SPARSEMEM_ENABLE
> > def_bool y
> > select SPARSEMEM_VMEMMAP_ENABLE
> > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> > index 1b94f5b82654..439325532be1 100644
> > --- a/arch/arm64/mm/pageattr.c
> > +++ b/arch/arm64/mm/pageattr.c
> > @@ -155,7 +155,7 @@ int set_direct_map_invalid_noflush(struct page *page)
> > .clear_mask = __pgprot(PTE_VALID),
> > };
> > - if (!rodata_full)
> > + if (!debug_pagealloc_enabled() && !rodata_full)
> > return 0;
> > return apply_to_page_range(&init_mm,
> > @@ -170,7 +170,7 @@ int set_direct_map_default_noflush(struct page *page)
> > .clear_mask = __pgprot(PTE_RDONLY),
> > };
> > - if (!rodata_full)
> > + if (!debug_pagealloc_enabled() && !rodata_full)
> > return 0;
> > return apply_to_page_range(&init_mm,
>
> I don't understand these two hunks. Previous patch calls this for
> hibernation when CONFIG_ARCH_HAS_SET_DIRECT_MAP, which is true for arm64.
> Why suddenly this starts to depend on debug_pagealloc_enabled()?
I was confused about this for quite a long :)
On arm64 the changes to direct^w linear map are allowed when
debug_page_alloc() || rodata_full
In hibernation we essentially have now
if (1)
set_direct_map(something)
else
debug_page_alloc_map()
With debug_pagealloc enabled but with rodata_full disabled arm64
versions of set_direct_map_*() will become a nop, so a page that was
unmapped by debug_pagealloc() will not be mapped back.
I'm still puzzled how hibernation might ever need to save a free page,
but that's another story.
--
Sincerely yours,
Mike.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-11-05 11:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 16:20 [PATCH v4 0/4] arch, mm: improve robustness of direct map manipulation Mike Rapoport
2020-11-03 16:20 ` [PATCH v4 1/4] mm: introduce debug_pagealloc_map_pages() helper Mike Rapoport
2020-11-04 17:35 ` Vlastimil Babka
2020-11-05 11:31 ` Mike Rapoport
2020-11-03 16:20 ` [PATCH v4 2/4] PM: hibernate: make direct map manipulations more explicit Mike Rapoport
2020-11-04 17:40 ` Vlastimil Babka
2020-11-05 11:33 ` Mike Rapoport
2020-11-03 16:20 ` [PATCH v4 3/4] arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC Mike Rapoport
2020-11-04 18:02 ` Vlastimil Babka
2020-11-05 11:42 ` Mike Rapoport [this message]
2020-11-03 16:20 ` [PATCH v4 4/4] arch, mm: make kernel_page_present() always available Mike Rapoport
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201105114200.GZ4879@kernel.org \
--to=rppt@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=aou@eecs.berkeley.edu \
--cc=benh@kernel.crashing.org \
--cc=borntraeger@de.ibm.com \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=cl@linux.com \
--cc=dave.hansen@linux.intel.com \
--cc=davem@davemloft.net \
--cc=david@redhat.com \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=hpa@zytor.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=len.brown@intel.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=linux-s390@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=palmer@dabbelt.com \
--cc=paul.walmsley@sifive.com \
--cc=paulus@samba.org \
--cc=pavel@ucw.cz \
--cc=penberg@kernel.org \
--cc=peterz@infradead.org \
--cc=rick.p.edgecombe@intel.com \
--cc=rientjes@google.com \
--cc=rjw@rjwysocki.net \
--cc=rppt@linux.ibm.com \
--cc=sparclinux@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=vbabka@suse.cz \
--cc=will@kernel.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).