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Date:   Mon, 29 Mar 2021 15:59:52 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Pavel Tatashin <pasha.tatashin@soleen.com>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-stable <stable@vger.kernel.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        David Hildenbrand <david@redhat.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Jason Wang <jasowang@redhat.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Oscar Salvador <osalvador@suse.de>,
        Pankaj Gupta <pankaj.gupta@cloud.ionos.com>,
        Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
        teawater <teawaterz@linux.alibaba.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Wei Yang <richard.weiyang@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.11 225/254] arm64/mm: define arch_get_mappable_range()
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On Mon, Mar 29, 2021 at 09:53:10AM -0400, Pavel Tatashin wrote:
> On Mon, Mar 29, 2021 at 9:51 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Mar 29, 2021 at 03:49:19PM +0200, Ard Biesheuvel wrote:
> > > (+ Pavel)
> > >
> > > On Mon, 29 Mar 2021 at 15:42, Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > On Mon, Mar 29, 2021 at 03:08:52PM +0200, Ard Biesheuvel wrote:
> > > > > On Mon, 29 Mar 2021 at 12:12, Greg Kroah-Hartman
> > > > > <gregkh@linuxfoundation.org> wrote:
> > > > > >
> > > > > > On Mon, Mar 29, 2021 at 03:05:25PM +0530, Naresh Kamboju wrote:
> > > > > > > On Mon, 29 Mar 2021 at 14:10, Greg Kroah-Hartman
> > > > > > > <gregkh@linuxfoundation.org> wrote:
> > > > > > > >
> > > > > > > > From: Anshuman Khandual <anshuman.khandual@arm.com>
> > > > > > > >
> > > > > > > > [ Upstream commit 03aaf83fba6e5af08b5dd174c72edee9b7d9ed9b ]
> > > > > > > >
> > > > > > > > This overrides arch_get_mappable_range() on arm64 platform which will be
> > > > > > > > used with recently added generic framework.  It drops
> > > > > > > > inside_linear_region() and subsequent check in arch_add_memory() which are
> > > > > > > > no longer required.  It also adds a VM_BUG_ON() check that would ensure
> > > > > > > > that mhp_range_allowed() has already been called.
> > > > > > > >
> > > > > > > > Link: https://lkml.kernel.org/r/1612149902-7867-3-git-send-email-anshuman.khandual@arm.com
> > > > > > > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> > > > > > > > Reviewed-by: David Hildenbrand <david@redhat.com>
> > > > > > > > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > > > > > > > Cc: Will Deacon <will@kernel.org>
> > > > > > > > Cc: Ard Biesheuvel <ardb@kernel.org>
> > > > > > > > Cc: Mark Rutland <mark.rutland@arm.com>
> > > > > > > > Cc: Heiko Carstens <hca@linux.ibm.com>
> > > > > > > > Cc: Jason Wang <jasowang@redhat.com>
> > > > > > > > Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > > > > > Cc: "Michael S. Tsirkin" <mst@redhat.com>
> > > > > > > > Cc: Michal Hocko <mhocko@kernel.org>
> > > > > > > > Cc: Oscar Salvador <osalvador@suse.de>
> > > > > > > > Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
> > > > > > > > Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> > > > > > > > Cc: teawater <teawaterz@linux.alibaba.com>
> > > > > > > > Cc: Vasily Gorbik <gor@linux.ibm.com>
> > > > > > > > Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> > > > > > > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > > > > > > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > > > > > > > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > > > > > > > ---
> > > > > > > >  arch/arm64/mm/mmu.c | 15 +++++++--------
> > > > > > > >  1 file changed, 7 insertions(+), 8 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > > > > > > > index 6f0648777d34..92b3be127796 100644
> > > > > > > > --- a/arch/arm64/mm/mmu.c
> > > > > > > > +++ b/arch/arm64/mm/mmu.c
> > > > > > > > @@ -1443,16 +1443,19 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
> > > > > > > >         free_empty_tables(start, end, PAGE_OFFSET, PAGE_END);
> > > > > > > >  }
> > > > > > > >
> > > > > > > > -static bool inside_linear_region(u64 start, u64 size)
> > > > > > > > +struct range arch_get_mappable_range(void)
> > > > > > > >  {
> > > > > > > > +       struct range mhp_range;
> > > > > > > > +
> > > > > > > >         /*
> > > > > > > >          * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
> > > > > > > >          * accommodating both its ends but excluding PAGE_END. Max physical
> > > > > > > >          * range which can be mapped inside this linear mapping range, must
> > > > > > > >          * also be derived from its end points.
> > > > > > > >          */
> > > > > > > > -       return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
> > > > > > > > -              (start + size - 1) <= __pa(PAGE_END - 1);
> > > > > > > > +       mhp_range.start = __pa(_PAGE_OFFSET(vabits_actual));
> > > > > > > > +       mhp_range.end =  __pa(PAGE_END - 1);
> > > > > > > > +       return mhp_range;
> > > > > > > >  }
> > > > > > > >
> > > > > > > >  int arch_add_memory(int nid, u64 start, u64 size,
> > > > > > > > @@ -1460,11 +1463,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
> > > > > > > >  {
> > > > > > > >         int ret, flags = 0;
> > > > > > > >
> > > > > > > > -       if (!inside_linear_region(start, size)) {
> > > > > > > > -               pr_err("[%llx %llx] is outside linear mapping region\n", start, start + size);
> > > > > > > > -               return -EINVAL;
> > > > > > > > -       }
> > > > > > > > -
> > > > > > > > +       VM_BUG_ON(!mhp_range_allowed(start, size, true));
> > > > > > > >         if (rodata_full || debug_pagealloc_enabled())
> > > > > > > >                 flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
> > > > > > >
> > > > > > > The stable rc 5.10 and 5.11 builds failed for arm64 architecture
> > > > > > > due to below warnings / errors,
> > > > > > >
> > > > > > > > Anshuman Khandual <anshuman.khandual@arm.com>
> > > > > > > >     arm64/mm: define arch_get_mappable_range()
> > > > > > >
> > > > > > >
> > > > > > >   arch/arm64/mm/mmu.c: In function 'arch_add_memory':
> > > > > > >   arch/arm64/mm/mmu.c:1483:13: error: implicit declaration of function
> > > > > > > 'mhp_range_allowed'; did you mean 'cpu_map_prog_allowed'?
> > > > > > > [-Werror=implicit-function-declaration]
> > > > > > >     VM_BUG_ON(!mhp_range_allowed(start, size, true));
> > > > > > >                ^
> > > > > > >   include/linux/build_bug.h:30:63: note: in definition of macro
> > > > > > > 'BUILD_BUG_ON_INVALID'
> > > > > > >    #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
> > > > > > >                                                                  ^
> > > > > > >   arch/arm64/mm/mmu.c:1483:2: note: in expansion of macro 'VM_BUG_ON'
> > > > > > >     VM_BUG_ON(!mhp_range_allowed(start, size, true));
> > > > > > >     ^~~~~~~~~
> > > > > > >
> > > > > > > Build link,
> > > > > > > https://ci.linaro.org/view/lkft/job/openembedded-lkft-linux-stable-rc-5.11/DISTRO=lkft,MACHINE=juno,label=docker-buster-lkft/41/consoleText
> > > > > > > https://ci.linaro.org/view/lkft/job/openembedded-lkft-linux-stable-rc-5.10/DISTRO=lkft,MACHINE=dragonboard-410c,label=docker-buster-lkft/120/consoleFull
> > > > > >
> > > > > > thanks, will go drop this, and the patch that was after it in the
> > > > > > series, from both trees and will push out a -rc2.
> > > > > >
> > > > >
> > > > > Why were these picked up in the first place? I don't see any fixes or
> > > > > cc:stable tags, and the commit log clearly describes that the change
> > > > > is preparatory work for enabling arm64 support into a recently
> > > > > introduced generic framework.
> > > >
> > > > This was needed for a follow-on patch in the series that fixed an issue.
> > > > Specifically it was commit ee7febce0519 ("arm64: mm: correct the inside
> > > > linear map range during hotplug check")
> > > >
> > >
> > > Yeah, but during the discussion of that patch [0], we pointed out that
> > > it needed to be rebased because of these new changes. So trying to
> > > backport this rebased version is obviously not the right approach:
> > > Pavel's original patch would be much more suitable for that.
> > >
> > > Could we have annotated this patch in a better way to make this more obvious?
> >
> > Yes, given that there was no annotation on the patch at all to let us
> > know this :)
> >
> > You can say things like "do not apply to stable trees" or "needs total
> > rework for older kernels" or other fun such things that when we read
> > them, we know to ask for help.  As it is, the patch provided nothing so
> > we guessed and got it wrong...
> 
> I will send the patch for stable trees with the commit id included as requested.

Wonderful, thank you so much.

greg k-h