From: Peter Zijlstra <peterz@infradead.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Fenghua Yu <fenghua.yu@intel.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH 12/15] kmap: Add stray write protection for device pages
Date: Tue, 14 Jul 2020 21:49:21 +0200 [thread overview]
Message-ID: <20200714194921.GJ5523@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <50d472d8-e4d9-dd35-f31f-268aa69c76e2@intel.com>
On Tue, Jul 14, 2020 at 12:42:11PM -0700, Dave Hansen wrote:
> On 7/14/20 12:29 PM, Peter Zijlstra wrote:
> > On Tue, Jul 14, 2020 at 12:06:16PM -0700, Ira Weiny wrote:
> >> On Tue, Jul 14, 2020 at 10:44:51AM +0200, Peter Zijlstra wrote:
> >>> So, if I followed along correctly, you're proposing to do a WRMSR per
> >>> k{,un}map{_atomic}(), sounds like excellent performance all-round :-(
> >> Only to pages which have this additional protection, ie not DRAM.
> >>
> >> User mappings of this memory is not affected (would be covered by User PKeys if
> >> desired). User mappings to persistent memory are the primary use case and the
> >> performant path.
> > Because performance to non-volatile memory doesn't matter? I think Dave
> > has a better answer here ...
>
> So, these WRMSRs are less evil than normal. They're architecturally
> non-serializing instructions,
Excellent, that should make these a fair bit faster than regular MSRs.
> But, either way, this *will* make accessing PMEM more expensive from the
> kernel. No escaping that.
There's no free lunch, it's just that regular MSRs are fairly horrible.
next prev parent reply other threads:[~2020-07-14 19:49 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 7:02 [RFC PATCH 00/15] PKS: Add Protection Keys Supervisor (PKS) support ira.weiny
2020-07-14 7:02 ` [RFC PATCH 01/15] x86/pkeys: Create pkeys_internal.h ira.weiny
2020-07-14 7:02 ` [RFC PATCH 02/15] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support ira.weiny
2020-07-14 7:02 ` [RFC PATCH 03/15] x86/pks: Enable Protection Keys Supervisor (PKS) ira.weiny
2020-07-14 7:02 ` [RFC PATCH 04/15] x86/pks: Preserve the PKRS MSR on context switch ira.weiny
2020-07-14 8:27 ` Peter Zijlstra
2020-07-14 18:53 ` Ira Weiny
2020-07-14 18:56 ` Dave Hansen
2020-07-14 19:05 ` Peter Zijlstra
2020-07-14 19:09 ` Ira Weiny
2020-07-16 8:37 ` [x86/pks] 061e3e0b92: leaking-addresses.dmesg.uncheckedMSRaccesserror:WRMSRto0x6e1(triedtowrite0x0000000055555554)atrIP:(write_pkrs+0x15/0x2b) kernel test robot
2020-07-14 7:02 ` [RFC PATCH 05/15] x86/pks: Add PKS kernel API ira.weiny
2020-07-14 7:02 ` [RFC PATCH 06/15] x86/pks: Add a debugfs file for allocated PKS keys ira.weiny
2020-07-14 7:02 ` [RFC PATCH 07/15] Documentation/pkeys: Update documentation for kernel pkeys ira.weiny
2020-07-14 7:02 ` [RFC PATCH 08/15] x86/pks: Add PKS Test code ira.weiny
2020-07-14 7:02 ` [RFC PATCH 09/15] fs/dax: Remove unused size parameter ira.weiny
2020-07-14 7:02 ` [RFC PATCH 10/15] drivers/dax: Expand lock scope to cover the use of addresses ira.weiny
2020-07-14 7:02 ` [RFC PATCH 11/15] memremap: Add zone device access protection ira.weiny
2020-07-14 8:40 ` Peter Zijlstra
2020-07-14 19:10 ` Ira Weiny
2020-07-14 19:40 ` Peter Zijlstra
2020-07-14 7:02 ` [RFC PATCH 12/15] kmap: Add stray write protection for device pages ira.weiny
2020-07-14 8:44 ` Peter Zijlstra
2020-07-14 19:06 ` Ira Weiny
2020-07-14 19:29 ` Peter Zijlstra
2020-07-14 19:42 ` Dave Hansen
2020-07-14 19:49 ` Peter Zijlstra [this message]
2020-07-14 20:00 ` Ira Weiny
2020-07-14 7:02 ` [RFC PATCH 13/15] dax: Stray write protection for dax_direct_access() ira.weiny
2020-07-14 7:02 ` [RFC PATCH 14/15] nvdimm/pmem: Stray write protection for pmem->virt_addr ira.weiny
2020-07-14 7:02 ` [RFC PATCH 15/15] [dax|pmem]: Enable stray write protection ira.weiny
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