From: Will Deacon <will.deacon@arm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-s390@vger.kernel.org,
Sebastian Ott <sebott@linux.vnet.ibm.com>
Subject: Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM)
Date: Wed, 24 Feb 2016 11:02:22 +0000 [thread overview]
Message-ID: <20160224110221.GF28310@arm.com> (raw)
In-Reply-To: <56CD8B43.9070509@de.ibm.com>
On Wed, Feb 24, 2016 at 11:51:47AM +0100, Christian Borntraeger wrote:
> On 02/24/2016 11:41 AM, Will Deacon wrote:
> > On Wed, Feb 24, 2016 at 11:16:34AM +0100, Christian Borntraeger wrote:
> >> Without that fix we would clearly have stale tlb entries, no?
> >
> > Yes, but AFAIU the sequence on arm64 is:
> >
> > 1. trans huge mapping (block mapping in arm64 speak)
> > 2. faulting entry (pmd_mknotpresent)
> > 3. tlb invalidation
> > 4. table entry mapping the same pages as (1).
> >
> > so if the microarchitecture we're on can tolerate a mixture of block
> > mappings and page mappings mapping the same VA to the same PA, then the
> > lack of TLB maintenance would go unnoticed. There are certainly systems
> > where that could cause an issue, but I believe the one I've been testing
> > on would be ok.
>
> So in essence you say it does not matter that you flush the wrong range in
> flush_pmd_tlb_range as long as it will be flushed later on when the pages
> really go away. Yes, then it really might be ok for arm64.
Indeed, although that's a property of the microarchitecture I'm using
rather than an architectural guarantee so the code should certainly be
fixed!
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-s390@vger.kernel.org,
Sebastian Ott <sebott@linux.vnet.ibm.com>
Subject: Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM)
Date: Wed, 24 Feb 2016 11:02:22 +0000 [thread overview]
Message-ID: <20160224110221.GF28310@arm.com> (raw)
In-Reply-To: <56CD8B43.9070509@de.ibm.com>
On Wed, Feb 24, 2016 at 11:51:47AM +0100, Christian Borntraeger wrote:
> On 02/24/2016 11:41 AM, Will Deacon wrote:
> > On Wed, Feb 24, 2016 at 11:16:34AM +0100, Christian Borntraeger wrote:
> >> Without that fix we would clearly have stale tlb entries, no?
> >
> > Yes, but AFAIU the sequence on arm64 is:
> >
> > 1. trans huge mapping (block mapping in arm64 speak)
> > 2. faulting entry (pmd_mknotpresent)
> > 3. tlb invalidation
> > 4. table entry mapping the same pages as (1).
> >
> > so if the microarchitecture we're on can tolerate a mixture of block
> > mappings and page mappings mapping the same VA to the same PA, then the
> > lack of TLB maintenance would go unnoticed. There are certainly systems
> > where that could cause an issue, but I believe the one I've been testing
> > on would be ok.
>
> So in essence you say it does not matter that you flush the wrong range in
> flush_pmd_tlb_range as long as it will be flushed later on when the pages
> really go away. Yes, then it really might be ok for arm64.
Indeed, although that's a property of the microarchitecture I'm using
rather than an architectural guarantee so the code should certainly be
fixed!
Will
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WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM)
Date: Wed, 24 Feb 2016 11:02:22 +0000 [thread overview]
Message-ID: <20160224110221.GF28310@arm.com> (raw)
In-Reply-To: <56CD8B43.9070509@de.ibm.com>
On Wed, Feb 24, 2016 at 11:51:47AM +0100, Christian Borntraeger wrote:
> On 02/24/2016 11:41 AM, Will Deacon wrote:
> > On Wed, Feb 24, 2016 at 11:16:34AM +0100, Christian Borntraeger wrote:
> >> Without that fix we would clearly have stale tlb entries, no?
> >
> > Yes, but AFAIU the sequence on arm64 is:
> >
> > 1. trans huge mapping (block mapping in arm64 speak)
> > 2. faulting entry (pmd_mknotpresent)
> > 3. tlb invalidation
> > 4. table entry mapping the same pages as (1).
> >
> > so if the microarchitecture we're on can tolerate a mixture of block
> > mappings and page mappings mapping the same VA to the same PA, then the
> > lack of TLB maintenance would go unnoticed. There are certainly systems
> > where that could cause an issue, but I believe the one I've been testing
> > on would be ok.
>
> So in essence you say it does not matter that you flush the wrong range in
> flush_pmd_tlb_range as long as it will be flushed later on when the pages
> really go away. Yes, then it really might be ok for arm64.
Indeed, although that's a property of the microarchitecture I'm using
rather than an architectural guarantee so the code should certainly be
fixed!
Will
next prev parent reply other threads:[~2016-02-24 11:02 UTC|newest]
Thread overview: 153+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-11 18:22 [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) Gerald Schaefer
2016-02-11 18:22 ` Gerald Schaefer
2016-02-11 18:22 ` Gerald Schaefer
2016-02-11 19:09 ` Kirill A. Shutemov
2016-02-11 19:09 ` Kirill A. Shutemov
2016-02-11 19:09 ` Kirill A. Shutemov
2016-02-11 19:12 ` Kirill A. Shutemov
2016-02-11 19:12 ` Kirill A. Shutemov
2016-02-11 19:12 ` Kirill A. Shutemov
2016-02-12 12:21 ` Sebastian Ott
2016-02-12 12:21 ` Sebastian Ott
2016-02-12 12:21 ` Sebastian Ott
2016-02-11 19:57 ` Gerald Schaefer
2016-02-11 19:57 ` Gerald Schaefer
2016-02-11 19:57 ` Gerald Schaefer
2016-02-12 4:04 ` Aneesh Kumar K.V
2016-02-12 4:04 ` Aneesh Kumar K.V
2016-02-12 4:04 ` Aneesh Kumar K.V
2016-02-12 11:59 ` Gerald Schaefer
2016-02-12 11:59 ` Gerald Schaefer
2016-02-12 11:59 ` Gerald Schaefer
2016-02-12 16:17 ` Aneesh Kumar K.V
2016-02-12 16:17 ` Aneesh Kumar K.V
2016-02-12 16:17 ` Aneesh Kumar K.V
2016-02-12 10:01 ` Will Deacon
2016-02-12 10:01 ` Will Deacon
2016-02-12 10:01 ` Will Deacon
2016-02-12 10:12 ` Sebastian Ott
2016-02-12 10:12 ` Sebastian Ott
2016-02-12 10:12 ` Sebastian Ott
2016-02-12 15:52 ` Will Deacon
2016-02-12 15:52 ` Will Deacon
2016-02-12 15:52 ` Will Deacon
2016-02-12 15:41 ` Kirill A. Shutemov
2016-02-12 15:41 ` Kirill A. Shutemov
2016-02-12 15:41 ` Kirill A. Shutemov
2016-02-12 15:57 ` Christian Borntraeger
2016-02-12 15:57 ` Christian Borntraeger
2016-02-12 15:57 ` Christian Borntraeger
2016-02-12 17:16 ` Gerald Schaefer
2016-02-12 17:16 ` Gerald Schaefer
2016-02-12 17:16 ` Gerald Schaefer
2016-02-12 23:15 ` Kirill A. Shutemov
2016-02-12 23:15 ` Kirill A. Shutemov
2016-02-12 23:15 ` Kirill A. Shutemov
2016-02-13 11:58 ` Sebastian Ott
2016-02-13 11:58 ` Sebastian Ott
2016-02-13 11:58 ` Sebastian Ott
2016-02-15 11:31 ` Kirill A. Shutemov
2016-02-15 11:31 ` Kirill A. Shutemov
2016-02-15 11:31 ` Kirill A. Shutemov
2016-02-15 16:38 ` Sebastian Ott
2016-02-15 16:38 ` Sebastian Ott
2016-02-15 16:38 ` Sebastian Ott
2016-02-15 18:37 ` Gerald Schaefer
2016-02-15 18:37 ` Gerald Schaefer
2016-02-15 18:37 ` Gerald Schaefer
2016-02-15 18:37 ` Gerald Schaefer
2016-02-15 21:35 ` Kirill A. Shutemov
2016-02-15 21:35 ` Kirill A. Shutemov
2016-02-15 21:35 ` Kirill A. Shutemov
2016-02-16 9:54 ` Sebastian Ott
2016-02-16 9:54 ` Sebastian Ott
2016-02-16 9:54 ` Sebastian Ott
2016-02-16 16:24 ` Gerald Schaefer
2016-02-16 16:24 ` Gerald Schaefer
2016-02-16 16:24 ` Gerald Schaefer
2016-02-16 16:24 ` Gerald Schaefer
2016-02-17 15:04 ` Kirill A. Shutemov
2016-02-17 15:04 ` Kirill A. Shutemov
2016-02-17 15:04 ` Kirill A. Shutemov
2016-02-17 19:04 ` Sebastian Ott
2016-02-17 19:04 ` Sebastian Ott
2016-02-17 19:04 ` Sebastian Ott
2016-02-16 18:46 ` Christian Borntraeger
2016-02-16 18:46 ` Christian Borntraeger
2016-02-16 18:46 ` Christian Borntraeger
2016-02-17 19:13 ` Gerald Schaefer
2016-02-17 19:13 ` Gerald Schaefer
2016-02-17 19:13 ` Gerald Schaefer
2016-02-17 23:58 ` Kirill A. Shutemov
2016-02-17 23:58 ` Kirill A. Shutemov
2016-02-17 23:58 ` Kirill A. Shutemov
2016-02-18 15:00 ` Gerald Schaefer
2016-02-18 15:00 ` Gerald Schaefer
2016-02-18 15:00 ` Gerald Schaefer
2016-02-18 17:06 ` Kirill A. Shutemov
2016-02-18 17:06 ` Kirill A. Shutemov
2016-02-18 17:06 ` Kirill A. Shutemov
2016-02-19 14:15 ` Sebastian Ott
2016-02-19 14:15 ` Sebastian Ott
2016-02-19 14:15 ` Sebastian Ott
2016-02-15 16:41 ` Gerald Schaefer
2016-02-15 16:41 ` Gerald Schaefer
2016-02-15 16:41 ` Gerald Schaefer
2016-02-23 10:32 ` Kirill A. Shutemov
2016-02-23 10:32 ` Kirill A. Shutemov
2016-02-23 10:32 ` Kirill A. Shutemov
2016-02-23 17:46 ` Linus Torvalds
2016-02-23 17:46 ` Linus Torvalds
2016-02-23 17:46 ` Linus Torvalds
2016-02-23 17:46 ` Linus Torvalds
2016-02-23 18:19 ` Gerald Schaefer
2016-02-23 18:19 ` Gerald Schaefer
2016-02-23 18:19 ` Gerald Schaefer
2016-02-23 18:47 ` Will Deacon
2016-02-23 18:47 ` Will Deacon
2016-02-23 18:47 ` Will Deacon
2016-02-25 15:49 ` Steve Capper
2016-02-25 15:49 ` Steve Capper
2016-02-25 15:49 ` Steve Capper
2016-02-25 15:49 ` Steve Capper
2016-02-25 16:01 ` Kirill A. Shutemov
2016-02-25 16:01 ` Kirill A. Shutemov
2016-02-25 16:01 ` Kirill A. Shutemov
2016-02-25 16:01 ` Kirill A. Shutemov
2016-02-25 16:08 ` Steve Capper
2016-02-25 16:08 ` Steve Capper
2016-02-25 16:08 ` Steve Capper
2016-02-25 16:08 ` Steve Capper
2016-02-23 19:33 ` Kirill A. Shutemov
2016-02-23 19:33 ` Kirill A. Shutemov
2016-02-23 19:33 ` Kirill A. Shutemov
2016-02-23 20:22 ` Will Deacon
2016-02-23 20:22 ` Will Deacon
2016-02-23 20:22 ` Will Deacon
2016-02-24 10:16 ` Christian Borntraeger
2016-02-24 10:16 ` Christian Borntraeger
2016-02-24 10:16 ` Christian Borntraeger
2016-02-24 10:41 ` Will Deacon
2016-02-24 10:41 ` Will Deacon
2016-02-24 10:41 ` Will Deacon
2016-02-24 10:51 ` Christian Borntraeger
2016-02-24 10:51 ` Christian Borntraeger
2016-02-24 10:51 ` Christian Borntraeger
2016-02-24 11:02 ` Will Deacon [this message]
2016-02-24 11:02 ` Will Deacon
2016-02-24 11:02 ` Will Deacon
2016-02-24 17:22 ` Aneesh Kumar K.V
2016-02-24 17:22 ` Aneesh Kumar K.V
2016-02-24 17:22 ` Aneesh Kumar K.V
2016-02-24 8:39 ` Martin Schwidefsky
2016-02-24 8:39 ` Martin Schwidefsky
2016-02-24 8:39 ` Martin Schwidefsky
2016-02-24 12:11 ` Sebastian Ott
2016-02-24 12:11 ` Sebastian Ott
2016-02-24 12:11 ` Sebastian Ott
2016-02-24 16:44 ` Gerald Schaefer
2016-02-24 16:44 ` Gerald Schaefer
2016-02-24 16:44 ` Gerald Schaefer
2016-02-24 8:22 ` Martin Schwidefsky
2016-02-24 8:22 ` Martin Schwidefsky
2016-02-24 8:22 ` Martin Schwidefsky
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