From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: David Laight <David.Laight@ACULAB.COM>, Andy Lutomirski <luto@kernel.org> Cc: "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-security-module@vger.kernel.org" <linux-security-module@vger.kernel.org>, "oleg@redhat.com" <oleg@redhat.com>, "x86@kernel.org" <x86@kernel.org> Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor Date: Wed, 29 Jul 2020 12:55:51 -0500 [thread overview] Message-ID: <98aa9d5e-6eb4-de29-2fc2-06f6dc52086f@linux.microsoft.com> (raw) In-Reply-To: <a159f2e8417746fb88f31a97c6f366ba@AcuMS.aculab.com> On 7/29/20 3:36 AM, David Laight wrote: > From: Madhavan T. Venkataraman >> Sent: 28 July 2020 19:52 > ... >> trampfd faults are instruction faults that go through a different code path than >> the one that calls handle_mm_fault(). Perhaps, it is the handle_mm_fault() that >> is time consuming. Could you clarify? > Given that the expectation is a few instructions in userspace > (eg to pick up the original arguments for a nested call) > the (probable) thousands of clocks taken by entering the > kernel (especially with page table separation) is a massive > delta. > > If entering the kernel were cheap no one would have added > the DSO functions for getting the time of day. I hear you. BTW, I did not say that the overhead was trivial. I only said that in most cases, applications may not mind that extra overhead. However, since multiple people have raised that as an issue, I will address it. I mentioned before that the kernel can actually supply the code page that sets the context and jumps to a PC and map it so the performance issue can be addressed. I was planning to do that as a future enhancement. If there is a consensus that I must address it immediately, I could do that. I will continue this discussion in my reply to Andy's email. Let us pick it up from there. Thanks. Madhavan > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales)
WARNING: multiple messages have this Message-ID (diff)
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: David Laight <David.Laight@ACULAB.COM>, Andy Lutomirski <luto@kernel.org> Cc: "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>, "x86@kernel.org" <x86@kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "oleg@redhat.com" <oleg@redhat.com>, "linux-security-module@vger.kernel.org" <linux-security-module@vger.kernel.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor Date: Wed, 29 Jul 2020 12:55:51 -0500 [thread overview] Message-ID: <98aa9d5e-6eb4-de29-2fc2-06f6dc52086f@linux.microsoft.com> (raw) In-Reply-To: <a159f2e8417746fb88f31a97c6f366ba@AcuMS.aculab.com> On 7/29/20 3:36 AM, David Laight wrote: > From: Madhavan T. Venkataraman >> Sent: 28 July 2020 19:52 > ... >> trampfd faults are instruction faults that go through a different code path than >> the one that calls handle_mm_fault(). Perhaps, it is the handle_mm_fault() that >> is time consuming. Could you clarify? > Given that the expectation is a few instructions in userspace > (eg to pick up the original arguments for a nested call) > the (probable) thousands of clocks taken by entering the > kernel (especially with page table separation) is a massive > delta. > > If entering the kernel were cheap no one would have added > the DSO functions for getting the time of day. I hear you. BTW, I did not say that the overhead was trivial. I only said that in most cases, applications may not mind that extra overhead. However, since multiple people have raised that as an issue, I will address it. I mentioned before that the kernel can actually supply the code page that sets the context and jumps to a PC and map it so the performance issue can be addressed. I was planning to do that as a future enhancement. If there is a consensus that I must address it immediately, I could do that. I will continue this discussion in my reply to Andy's email. Let us pick it up from there. Thanks. Madhavan > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) _______________________________________________ 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:[~2020-07-29 17:55 UTC|newest] Thread overview: 146+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <aefc85852ea518982e74b233e11e16d2e707bc32> 2020-07-28 13:10 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 13:10 ` [PATCH v1 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 14:50 ` Oleg Nesterov 2020-07-28 14:50 ` Oleg Nesterov 2020-07-28 14:58 ` Madhavan T. Venkataraman 2020-07-28 14:58 ` Madhavan T. Venkataraman 2020-07-28 16:06 ` Oleg Nesterov 2020-07-28 16:06 ` Oleg Nesterov 2020-07-28 19:48 ` kernel test robot 2020-07-29 2:33 ` kernel test robot 2020-07-28 13:10 ` [PATCH v1 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 18:38 ` kernel test robot 2020-07-30 9:06 ` Greg KH 2020-07-30 9:06 ` Greg KH 2020-07-30 14:25 ` Madhavan T. Venkataraman 2020-07-30 14:25 ` Madhavan T. Venkataraman 2020-07-28 13:10 ` [PATCH v1 3/4] [RFC] arm64/trampfd: " madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 13:10 ` [PATCH v1 4/4] [RFC] arm/trampfd: " madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 15:13 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor David Laight 2020-07-28 15:13 ` David Laight 2020-07-28 15:13 ` David Laight 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:39 ` Madhavan T. Venkataraman 2020-07-29 5:16 ` Andy Lutomirski 2020-07-29 5:16 ` Andy Lutomirski 2020-07-29 5:16 ` Andy Lutomirski 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-29 8:36 ` David Laight 2020-07-29 8:36 ` David Laight 2020-07-29 8:36 ` David Laight 2020-07-29 17:55 ` Madhavan T. Venkataraman [this message] 2020-07-29 17:55 ` Madhavan T. Venkataraman 2020-07-29 17:55 ` Madhavan T. Venkataraman 2020-07-28 16:05 ` Casey Schaufler 2020-07-28 16:05 ` Casey Schaufler 2020-07-28 16:49 ` Madhavan T. Venkataraman 2020-07-28 16:49 ` Madhavan T. Venkataraman 2020-07-28 17:05 ` James Morris 2020-07-28 17:05 ` James Morris 2020-07-28 17:08 ` Madhavan T. Venkataraman 2020-07-28 17:08 ` Madhavan T. Venkataraman 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 19:01 ` Madhavan T. Venkataraman 2020-07-28 19:01 ` Madhavan T. Venkataraman 2020-07-29 13:29 ` Florian Weimer 2020-07-29 13:29 ` Florian Weimer 2020-07-29 13:29 ` Florian Weimer 2020-07-30 13:09 ` David Laight 2020-07-30 13:09 ` David Laight 2020-08-02 11:56 ` Pavel Machek 2020-08-02 11:56 ` Pavel Machek 2020-08-03 8:08 ` David Laight 2020-08-03 8:08 ` David Laight 2020-08-03 15:57 ` Madhavan T. Venkataraman 2020-08-03 15:57 ` Madhavan T. Venkataraman 2020-07-30 14:24 ` Madhavan T. Venkataraman 2020-07-30 20:54 ` Andy Lutomirski 2020-07-30 20:54 ` Andy Lutomirski 2020-07-30 20:54 ` Andy Lutomirski 2020-07-31 17:13 ` Madhavan T. Venkataraman 2020-07-31 17:13 ` Madhavan T. Venkataraman 2020-07-31 18:31 ` Mark Rutland 2020-07-31 18:31 ` Mark Rutland 2020-08-03 8:27 ` David Laight 2020-08-03 8:27 ` David Laight 2020-08-03 16:03 ` Madhavan T. Venkataraman 2020-08-03 16:03 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` David Laight 2020-08-03 16:57 ` David Laight 2020-08-03 17:00 ` Madhavan T. Venkataraman 2020-08-03 17:00 ` Madhavan T. Venkataraman 2020-08-03 17:58 ` Madhavan T. Venkataraman 2020-08-03 17:58 ` Madhavan T. Venkataraman 2020-08-04 13:55 ` Mark Rutland 2020-08-04 13:55 ` Mark Rutland 2020-08-04 14:33 ` David Laight 2020-08-04 14:33 ` David Laight 2020-08-04 14:44 ` David Laight 2020-08-04 14:44 ` David Laight 2020-08-04 14:48 ` Madhavan T. Venkataraman 2020-08-04 14:48 ` Madhavan T. Venkataraman 2020-08-04 15:46 ` Madhavan T. Venkataraman 2020-08-04 15:46 ` Madhavan T. Venkataraman 2020-08-02 13:57 ` Florian Weimer 2020-08-02 13:57 ` Florian Weimer 2020-08-02 13:57 ` Florian Weimer 2020-07-30 14:42 ` Madhavan T. Venkataraman 2020-07-30 14:42 ` Madhavan T. Venkataraman 2020-08-02 18:54 ` Madhavan T. Venkataraman 2020-08-02 18:54 ` Madhavan T. Venkataraman 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 22:58 ` Madhavan T. Venkataraman 2020-08-02 22:58 ` Madhavan T. Venkataraman 2020-08-03 18:36 ` Madhavan T. Venkataraman 2020-08-03 18:36 ` Madhavan T. Venkataraman 2020-08-10 17:20 ` Madhavan T. Venkataraman 2020-08-10 17:34 ` Madhavan T. Venkataraman 2020-08-10 17:34 ` Madhavan T. Venkataraman 2020-08-11 21:12 ` Madhavan T. Venkataraman 2020-08-11 21:12 ` Madhavan T. Venkataraman 2020-08-03 8:23 ` David Laight 2020-08-03 8:23 ` David Laight 2020-08-03 15:59 ` Madhavan T. Venkataraman 2020-08-03 15:59 ` Madhavan T. Venkataraman 2020-07-31 18:09 ` Mark Rutland 2020-07-31 18:09 ` Mark Rutland 2020-07-31 20:08 ` Madhavan T. Venkataraman 2020-07-31 20:08 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` Madhavan T. Venkataraman 2020-08-04 14:30 ` Mark Rutland 2020-08-04 14:30 ` Mark Rutland 2020-08-06 17:26 ` Madhavan T. Venkataraman 2020-08-06 17:26 ` Madhavan T. Venkataraman 2020-08-08 22:17 ` Pavel Machek 2020-08-08 22:17 ` Pavel Machek 2020-08-11 12:41 ` Madhavan T. Venkataraman 2020-08-11 12:41 ` Madhavan T. Venkataraman 2020-08-11 13:08 ` Pavel Machek 2020-08-11 13:08 ` Pavel Machek 2020-08-11 15:54 ` Madhavan T. Venkataraman 2020-08-11 15:54 ` Madhavan T. Venkataraman 2020-08-12 10:06 ` Mark Rutland 2020-08-12 10:06 ` Mark Rutland 2020-08-12 18:47 ` Madhavan T. Venkataraman 2020-08-12 18:47 ` Madhavan T. Venkataraman 2020-08-19 18:53 ` Mickaël Salaün 2020-08-19 18:53 ` Mickaël Salaün 2020-09-01 15:42 ` Mark Rutland 2020-09-01 15:42 ` Mark Rutland
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