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From: Paolo Bonzini <pbonzini@redhat.com>
To: Dominik Dingel <dingel@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Mel Gorman <mgorman@suse.de>,
	Michal Hocko <mhocko@suse.cz>,
	Dave Hansen <dave.hansen@intel.com>,
	Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Bob Liu <lliubbo@gmail.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Gleb Natapov <gleb@kernel.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@kernel.org>,
	Jianyu Zhan <nasa4836@gmail.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Konstantin Weitz <konstantin.weitz@gmail.com>,
	kvm@vger.kernel.org, linux390@de.ibm.com,
	linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH 3/4] s390/mm: prevent and break zero page mappings in case of storage keys
Date: Wed, 22 Oct 2014 12:09:31 +0200	[thread overview]
Message-ID: <5447825B.5040608@redhat.com> (raw)
In-Reply-To: <1413966624-12447-4-git-send-email-dingel@linux.vnet.ibm.com>

On 10/22/2014 10:30 AM, Dominik Dingel wrote:
> As use_skey is already the condition on which we call s390_enable_skey
> we need to introduce a new flag for the mm->context on which we decide
> if zero page mapping is allowed.

Can you explain better why "mm->context.use_skey = 1" cannot be done
before the walk_page_range?  Where does the walk or __s390_enable_skey
or (after the next patch) ksm_madvise rely on
"mm->context.forbids_zeropage && !mm->context.use_skey"?

The only reason I can think of, is that the next patch does not reset
"mm->context.forbids_zeropage" to 0 if the ksm_madvise fails.  Why
doesn't it do that---or is it a bug?

Thanks, and sorry for the flurry of questions! :)

Paolo

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WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Dominik Dingel <dingel@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Mel Gorman <mgorman@suse.de>,
	Michal Hocko <mhocko@suse.cz>,
	Dave Hansen <dave.hansen@intel.com>,
	Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Bob Liu <lliubbo@gmail.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Gleb Natapov <gleb@kernel.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@kernel.org>,
	Jianyu Zhan <nasa4836@gmail.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Konstantin Weitz <konstantin.weitz@gmail.com>,
	kvm@vger.kernel.org, linux390@de.ibm.com,
	linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH 3/4] s390/mm: prevent and break zero page mappings in case of storage keys
Date: Wed, 22 Oct 2014 12:09:31 +0200	[thread overview]
Message-ID: <5447825B.5040608@redhat.com> (raw)
In-Reply-To: <1413966624-12447-4-git-send-email-dingel@linux.vnet.ibm.com>

On 10/22/2014 10:30 AM, Dominik Dingel wrote:
> As use_skey is already the condition on which we call s390_enable_skey
> we need to introduce a new flag for the mm->context on which we decide
> if zero page mapping is allowed.

Can you explain better why "mm->context.use_skey = 1" cannot be done
before the walk_page_range?  Where does the walk or __s390_enable_skey
or (after the next patch) ksm_madvise rely on
"mm->context.forbids_zeropage && !mm->context.use_skey"?

The only reason I can think of, is that the next patch does not reset
"mm->context.forbids_zeropage" to 0 if the ksm_madvise fails.  Why
doesn't it do that---or is it a bug?

Thanks, and sorry for the flurry of questions! :)

Paolo

  parent reply	other threads:[~2014-10-22 10:09 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-22  8:30 [PATCH v2 0/4] mm: new function to forbid zeropage mappings for a process Dominik Dingel
2014-10-22  8:30 ` Dominik Dingel
2014-10-22  8:30 ` Dominik Dingel
2014-10-22  8:30 ` Dominik Dingel
2014-10-22  8:30 ` [PATCH 1/4] s390/mm: recfactor global pgste updates Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30 ` [PATCH 2/4] mm: introduce mm_forbids_zeropage function Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30 ` [PATCH 3/4] s390/mm: prevent and break zero page mappings in case of storage keys Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22 10:09   ` Paolo Bonzini
2014-10-22 10:09     ` Paolo Bonzini
2014-10-22 10:09   ` Paolo Bonzini [this message]
2014-10-22 10:09     ` Paolo Bonzini
2014-10-22 10:32     ` Dominik Dingel
2014-10-22 10:32       ` Dominik Dingel
2014-10-22 10:32       ` Dominik Dingel
2014-10-22  8:30 ` [PATCH 4/4] s390/mm: disable KSM for storage key enabled pages Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
2014-10-22  8:30   ` Dominik Dingel
  -- strict thread matches above, loose matches on Subject: below --
2014-10-22 11:09 [PATCH v3 0/4] mm: new function to forbid zeropage mappings for a process Dominik Dingel
2014-10-22 11:09 ` [PATCH 3/4] s390/mm: prevent and break zero page mappings in case of storage keys Dominik Dingel
2014-10-22 11:09   ` Dominik Dingel
2014-10-22 11:09   ` Dominik Dingel
2014-10-22 11:09   ` Dominik Dingel
2014-10-22 14:00   ` Paolo Bonzini
2014-10-22 14:00     ` Paolo Bonzini
2014-10-22 14:00     ` Paolo Bonzini
2014-10-22 14:00     ` Paolo Bonzini
2014-10-17 14:09 [PATCH 0/4] mm: new flag to forbid zero page mappings for a vma Dominik Dingel
2014-10-17 14:09 ` [PATCH 3/4] s390/mm: prevent and break zero page mappings in case of storage keys Dominik Dingel
2014-10-17 14:09   ` Dominik Dingel
2014-10-17 14:09   ` Dominik Dingel
2014-10-17 14:09   ` Dominik Dingel

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