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[209.132.183.28]) by mx.google.com with ESMTPS id s55si1671812qth.127.2017.06.14.19.09.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Jun 2017 19:09:30 -0700 (PDT) Date: Wed, 14 Jun 2017 22:09:25 -0400 From: Jerome Glisse Subject: Re: [HMM-CDM 5/5] mm/hmm: simplify kconfig and enable HMM and DEVICE_PUBLIC for ppc64 Message-ID: <20170615020925.GC4666@redhat.com> References: <20170614201144.9306-1-jglisse@redhat.com> <20170614201144.9306-6-jglisse@redhat.com> <9aeed880-c200-a070-a7a4-212ee38c15ed@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9aeed880-c200-a070-a7a4-212ee38c15ed@nvidia.com> Sender: owner-linux-mm@kvack.org List-ID: To: John Hubbard Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Nellans , Balbir Singh , Aneesh Kumar , "Paul E . McKenney" , Benjamin Herrenschmidt On Wed, Jun 14, 2017 at 04:10:32PM -0700, John Hubbard wrote: > On 06/14/2017 01:11 PM, Jerome Glisse wrote: > > This just simplify kconfig and allow HMM and DEVICE_PUBLIC to be > > selected for ppc64 once ZONE_DEVICE is allowed on ppc64 (different > > patchset). > > > > Signed-off-by: Jerome Glisse > > Signed-off-by: John Hubbard > > Cc: Balbir Singh > > Cc: Aneesh Kumar > > Cc: Paul E. McKenney > > Cc: Benjamin Herrenschmidt > > --- > > include/linux/hmm.h | 4 ++-- > > mm/Kconfig | 27 ++++++--------------------- > > mm/hmm.c | 4 ++-- > > 3 files changed, 10 insertions(+), 25 deletions(-) > > > > diff --git a/include/linux/hmm.h b/include/linux/hmm.h > > index f6713b2..720d18c 100644 > > --- a/include/linux/hmm.h > > +++ b/include/linux/hmm.h > > @@ -327,7 +327,7 @@ int hmm_vma_fault(struct vm_area_struct *vma, > > #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ > > -#if IS_ENABLED(CONFIG_HMM_DEVMEM) > > +#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC) > > struct hmm_devmem; > > struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma, > > @@ -456,7 +456,7 @@ struct hmm_device { > > */ > > struct hmm_device *hmm_device_new(void *drvdata); > > void hmm_device_put(struct hmm_device *hmm_device); > > -#endif /* IS_ENABLED(CONFIG_HMM_DEVMEM) */ > > +#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */ > > /* Below are for HMM internal use only! Not to be used by device driver! */ > > diff --git a/mm/Kconfig b/mm/Kconfig > > index ad082b9..7de939a 100644 > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -265,7 +265,7 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION > > config ARCH_HAS_HMM > > bool > > default y > > - depends on X86_64 > > + depends on X86_64 || PPC64 > > depends on ZONE_DEVICE > > depends on MMU && 64BIT > > depends on MEMORY_HOTPLUG > > @@ -277,7 +277,7 @@ config HMM > > config HMM_MIRROR > > bool "HMM mirror CPU page table into a device page table" > > - depends on ARCH_HAS_HMM > > + depends on ARCH_HAS_HMM && X86_64 > > select MMU_NOTIFIER > > select HMM > > help > > Hi Jerome, > > There are still some problems with using this configuration. First and > foremost, it is still possible (and likely, given the complete dissimilarity > in naming, and difference in location on the screen) to choose HMM_MIRROR, > and *not* to choose either DEVICE_PRIVATE or DEVICE_PUBLIC. And then we end > up with a swath of important page fault handling code being ifdef'd out, and > one ends up having to investigate why. > > As for solutions, at least for the x86 (DEVICE_PRIVATE)case, we could do this: > > diff --git a/mm/Kconfig b/mm/Kconfig > index 7de939a29466..f64182d7b956 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -279,6 +279,7 @@ config HMM_MIRROR > bool "HMM mirror CPU page table into a device page table" > depends on ARCH_HAS_HMM && X86_64 > select MMU_NOTIFIER > + select DEVICE_PRIVATE > select HMM > help > Select HMM_MIRROR if you want to mirror range of the CPU page table of a > > ...and that is better than the other direction (having HMM_MIRROR depend on > DEVICE_PRIVATE), because in the latter case, HMM_MIRROR will disappear (and > it's several lines above) until you select DEVICE_PRIVATE. That is hard to > work with for the user. > > The user will tend to select HMM_MIRROR, but it is *not* obvious that he/she > should also select DEVICE_PRIVATE. So Kconfig should do it for them. > > In fact, I'm not even sure if the DEVICE_PRIVATE and DEVICE_PUBLIC actually > need Kconfig protection, but if they don't, then life would be easier for > whoever is configuring their kernel. > We do need Kconfig for DEVICE_PRIVATE and DEVICE_PUBLIC. I can remove HMM_MIRROR and have HMM mirror code ifdef on DEVICE_PRIVATE. Cheers, Jerome -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org