From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
linux-s390@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Dan Williams <dan.j.williams@intel.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Eric Badger <ebadger@gigaio.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA
Date: Thu, 27 Feb 2020 17:54:40 +0000 [thread overview]
Message-ID: <7e573498-81c1-7f00-c1ff-ed16e12a5b96@deltatee.com> (raw)
In-Reply-To: <20200227174311.GL31668@ziepe.ca>
On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote:
> Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in
> Linux, so while it is true the memory has no side effects, there would
> be surprising concurrency risks if anything in the kernel tried to
> write to it.
>
> Not compatible means the locks don't contain stores to WC memory the
> way you would expect. AFAIK on many CPUs extra barriers are required
> to keep WC stores ordered, the same way ARM already has extra barriers
> to keep UC stores ordered with locking..
>
> The spinlocks are defined to contain UC stores though.
>
> If there is no actual need today for WC I would suggest using UC as
> the default.
Ok, that sounds sensible. I'll do that in the next revision.
Thanks,
Logan
WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
linux-sh@vger.kernel.org, platform-driver-x86@vger.kernel.org,
linux-mm@kvack.org, Dan Williams <dan.j.williams@intel.com>,
Michal Hocko <mhocko@kernel.org>,
David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Eric Badger <ebadger@gigaio.com>
Subject: Re: [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA
Date: Thu, 27 Feb 2020 10:54:40 -0700 [thread overview]
Message-ID: <7e573498-81c1-7f00-c1ff-ed16e12a5b96@deltatee.com> (raw)
In-Reply-To: <20200227174311.GL31668@ziepe.ca>
On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote:
> Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in
> Linux, so while it is true the memory has no side effects, there would
> be surprising concurrency risks if anything in the kernel tried to
> write to it.
>
> Not compatible means the locks don't contain stores to WC memory the
> way you would expect. AFAIK on many CPUs extra barriers are required
> to keep WC stores ordered, the same way ARM already has extra barriers
> to keep UC stores ordered with locking..
>
> The spinlocks are defined to contain UC stores though.
>
> If there is no actual need today for WC I would suggest using UC as
> the default.
Ok, that sounds sensible. I'll do that in the next revision.
Thanks,
Logan
WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
linux-s390@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Dan Williams <dan.j.williams@intel.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Eric Badger <ebadger@gigaio.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA
Date: Thu, 27 Feb 2020 10:54:40 -0700 [thread overview]
Message-ID: <7e573498-81c1-7f00-c1ff-ed16e12a5b96@deltatee.com> (raw)
In-Reply-To: <20200227174311.GL31668@ziepe.ca>
On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote:
> Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in
> Linux, so while it is true the memory has no side effects, there would
> be surprising concurrency risks if anything in the kernel tried to
> write to it.
>
> Not compatible means the locks don't contain stores to WC memory the
> way you would expect. AFAIK on many CPUs extra barriers are required
> to keep WC stores ordered, the same way ARM already has extra barriers
> to keep UC stores ordered with locking..
>
> The spinlocks are defined to contain UC stores though.
>
> If there is no actual need today for WC I would suggest using UC as
> the default.
Ok, that sounds sensible. I'll do that in the next revision.
Thanks,
Logan
WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
linux-s390@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Eric Badger <ebadger@gigaio.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA
Date: Thu, 27 Feb 2020 10:54:40 -0700 [thread overview]
Message-ID: <7e573498-81c1-7f00-c1ff-ed16e12a5b96@deltatee.com> (raw)
In-Reply-To: <20200227174311.GL31668@ziepe.ca>
On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote:
> Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in
> Linux, so while it is true the memory has no side effects, there would
> be surprising concurrency risks if anything in the kernel tried to
> write to it.
>
> Not compatible means the locks don't contain stores to WC memory the
> way you would expect. AFAIK on many CPUs extra barriers are required
> to keep WC stores ordered, the same way ARM already has extra barriers
> to keep UC stores ordered with locking..
>
> The spinlocks are defined to contain UC stores though.
>
> If there is no actual need today for WC I would suggest using UC as
> the default.
Ok, that sounds sensible. I'll do that in the next revision.
Thanks,
Logan
WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
linux-s390@vger.kernel.org, David Hildenbrand <david@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Dan Williams <dan.j.williams@intel.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Eric Badger <ebadger@gigaio.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA
Date: Thu, 27 Feb 2020 10:54:40 -0700 [thread overview]
Message-ID: <7e573498-81c1-7f00-c1ff-ed16e12a5b96@deltatee.com> (raw)
In-Reply-To: <20200227174311.GL31668@ziepe.ca>
On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote:
> Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in
> Linux, so while it is true the memory has no side effects, there would
> be surprising concurrency risks if anything in the kernel tried to
> write to it.
>
> Not compatible means the locks don't contain stores to WC memory the
> way you would expect. AFAIK on many CPUs extra barriers are required
> to keep WC stores ordered, the same way ARM already has extra barriers
> to keep UC stores ordered with locking..
>
> The spinlocks are defined to contain UC stores though.
>
> If there is no actual need today for WC I would suggest using UC as
> the default.
Ok, that sounds sensible. I'll do that in the next revision.
Thanks,
Logan
_______________________________________________
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:[~2020-02-27 17:54 UTC|newest]
Thread overview: 148+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 18:24 [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` [PATCH v3 1/7] mm/memory_hotplug: Drop the flags field from struct mhp_restrictions Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-28 21:31 ` Dan Williams
2020-02-28 21:31 ` Dan Williams
2020-02-28 21:31 ` Dan Williams
2020-02-28 21:31 ` Dan Williams
2020-02-28 21:31 ` Dan Williams
2020-02-28 21:31 ` Dan Williams
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-02-21 18:24 ` [PATCH v3 2/7] mm/memory_hotplug: Rename mhp_restrictions to mhp_params Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-24 9:11 ` David Hildenbrand
2020-02-24 9:11 ` David Hildenbrand
2020-02-24 9:11 ` David Hildenbrand
2020-02-24 9:11 ` David Hildenbrand
2020-02-29 20:44 ` Dan Williams
2020-02-29 20:44 ` Dan Williams
2020-02-29 20:44 ` Dan Williams
2020-02-29 20:44 ` Dan Williams
2020-02-29 20:44 ` Dan Williams
2020-02-29 20:44 ` Dan Williams
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-03-03 9:50 ` Michal Hocko
2020-02-21 18:24 ` [PATCH v3 3/7] x86/mm: Thread pgprot_t through init_memory_mapping() Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-21 18:24 ` Logan Gunthorpe
2020-02-29 22:37 ` Dan Williams
2020-02-29 22:37 ` Dan Williams
2020-02-29 22:37 ` Dan Williams
2020-02-29 22:37 ` Dan Williams
2020-02-29 22:37 ` Dan Williams
2020-02-29 22:37 ` Dan Williams
2020-03-03 9:52 ` Michal Hocko
2020-03-03 9:52 ` Michal Hocko
2020-03-03 9:52 ` Michal Hocko
2020-03-03 9:52 ` Michal Hocko
2020-03-03 9:52 ` Michal Hocko
2020-02-21 18:25 ` [PATCH v3 4/7] x86/mm: Introduce _set_memory_prot() Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-29 22:33 ` Dan Williams
2020-02-29 22:33 ` Dan Williams
2020-02-29 22:33 ` Dan Williams
2020-02-29 22:33 ` Dan Williams
2020-02-29 22:33 ` Dan Williams
2020-02-29 22:33 ` Dan Williams
2020-03-02 18:46 ` Logan Gunthorpe
2020-03-02 18:46 ` Logan Gunthorpe
2020-03-02 18:46 ` Logan Gunthorpe
2020-03-02 18:46 ` Logan Gunthorpe
2020-03-02 18:46 ` Logan Gunthorpe
2020-02-21 18:25 ` [PATCH v3 5/7] powerpc/mm: Thread pgprot_t through create_section_mapping() Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` [PATCH v3 6/7] mm/memory_hotplug: Add pgprot_t to mhp_params Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-24 9:26 ` David Hildenbrand
2020-02-24 9:26 ` David Hildenbrand
2020-02-24 9:26 ` David Hildenbrand
2020-02-24 9:26 ` David Hildenbrand
2020-02-29 22:44 ` Dan Williams
2020-02-29 22:44 ` Dan Williams
2020-02-29 22:44 ` Dan Williams
2020-02-29 22:44 ` Dan Williams
2020-02-29 22:44 ` Dan Williams
2020-02-29 22:44 ` Dan Williams
2020-03-02 18:55 ` Logan Gunthorpe
2020-03-02 18:55 ` Logan Gunthorpe
2020-03-02 18:55 ` Logan Gunthorpe
2020-03-02 18:55 ` Logan Gunthorpe
2020-03-02 18:55 ` Logan Gunthorpe
2020-03-02 20:26 ` Dan Williams
2020-03-02 20:26 ` Dan Williams
2020-03-02 20:26 ` Dan Williams
2020-03-02 20:26 ` Dan Williams
2020-03-02 20:26 ` Dan Williams
2020-03-02 20:26 ` Dan Williams
2020-02-21 18:25 ` [PATCH v3 7/7] mm/memremap: Set caching mode for PCI P2PDMA memory to WC Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-21 18:25 ` Logan Gunthorpe
2020-02-29 22:47 ` Dan Williams
2020-02-29 22:47 ` Dan Williams
2020-02-29 22:47 ` Dan Williams
2020-02-29 22:47 ` Dan Williams
2020-02-29 22:47 ` Dan Williams
2020-02-29 22:47 ` Dan Williams
2020-03-02 21:20 ` Logan Gunthorpe
2020-03-02 21:20 ` Logan Gunthorpe
2020-03-02 21:20 ` Logan Gunthorpe
2020-03-02 21:20 ` Logan Gunthorpe
2020-03-02 21:20 ` Logan Gunthorpe
2020-02-27 17:17 ` [PATCH v3 0/7] Allow setting caching mode in arch_add_memory() for P2PDMA Jason Gunthorpe
2020-02-27 17:17 ` Jason Gunthorpe
2020-02-27 17:17 ` Jason Gunthorpe
2020-02-27 17:17 ` Jason Gunthorpe
2020-02-27 17:17 ` Jason Gunthorpe
2020-02-27 17:21 ` Logan Gunthorpe
2020-02-27 17:21 ` Logan Gunthorpe
2020-02-27 17:21 ` Logan Gunthorpe
2020-02-27 17:21 ` Logan Gunthorpe
2020-02-27 17:21 ` Logan Gunthorpe
2020-02-27 17:43 ` Jason Gunthorpe
2020-02-27 17:43 ` Jason Gunthorpe
2020-02-27 17:43 ` Jason Gunthorpe
2020-02-27 17:43 ` Jason Gunthorpe
2020-02-27 17:43 ` Jason Gunthorpe
2020-02-27 17:54 ` Logan Gunthorpe [this message]
2020-02-27 17:54 ` Logan Gunthorpe
2020-02-27 17:54 ` Logan Gunthorpe
2020-02-27 17:54 ` Logan Gunthorpe
2020-02-27 17:54 ` Logan Gunthorpe
2020-02-27 17:55 ` Dan Williams
2020-02-27 17:55 ` Dan Williams
2020-02-27 17:55 ` Dan Williams
2020-02-27 17:55 ` Dan Williams
2020-02-27 17:55 ` Dan Williams
2020-02-27 17:55 ` Dan Williams
2020-02-27 18:03 ` Jason Gunthorpe
2020-02-27 18:03 ` Jason Gunthorpe
2020-02-27 18:03 ` Jason Gunthorpe
2020-02-27 18:03 ` Jason Gunthorpe
2020-02-27 18:03 ` Jason Gunthorpe
2020-02-27 18:08 ` Dan Williams
2020-02-27 18:08 ` Dan Williams
2020-02-27 18:08 ` Dan Williams
2020-02-27 18:08 ` Dan Williams
2020-02-27 18:08 ` Dan Williams
2020-02-27 18:08 ` Dan Williams
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