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Groups > linux.kernel > #1535220
| From | Linus Torvalds <torvalds@linux-foundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation |
| Date | 2016-12-02 22:20 +0100 |
| Message-ID | <sK3pn-D9-27@gated-at.bofh.it> (permalink) |
| References | (9 earlier) <sK1GV-7VR-27@gated-at.bofh.it> <sK1GV-7VR-25@gated-at.bofh.it> <sK1QB-7Z6-25@gated-at.bofh.it> <sK1QB-7Z6-23@gated-at.bofh.it> <sK2Wl-dS-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Dec 2, 2016 at 12:41 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> Because, if so, we should maybe serialize whenever we migrate a
> process to a different CPU.
The intel docs are bad on this issue.
Technically what we do could fall under the "cross-modifying code"
case, where one CPU does the write, and then we run it on another CPU.
And no, we do *not* do a serializing instruction before returning to
user space. Sure, we might do an iret (which is serializing), but we
equally well might be doing a systret (which is not).
Honestly, I think Intel should clean up their documentation.
> (We *definitely* need to flush the store buffer when migrating,
There is no such thing as flushing the store buffer.
But we do end up doing a memory barrier which gives you the required
semantics. That's not a problem. Those operations are fast. The
serializing instructions are not.
Linus
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[PATCH 0/4] CPUID-less CPU fixes and improvements Andy Lutomirski <luto@kernel.org> - 2016-11-30 21:40 +0100
[PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize Andy Lutomirski <luto@kernel.org> - 2016-11-30 21:40 +0100
Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize Borislav Petkov <bp@alien8.de> - 2016-12-01 10:30 +0100
Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize Andy Lutomirski <luto@amacapital.net> - 2016-12-01 18:10 +0100
Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-01 18:50 +0100
Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize Ingo Molnar <mingo@kernel.org> - 2016-12-02 08:40 +0100
[PATCH 3/4] x86/microcode/intel: Replace sync_core() with cpuid_eax(1) Andy Lutomirski <luto@kernel.org> - 2016-11-30 21:40 +0100
Re: [PATCH 3/4] x86/microcode/intel: Replace sync_core() with cpuid_eax(1) Borislav Petkov <bp@alien8.de> - 2016-12-01 10:20 +0100
[PATCH v2 6/6] x86/asm: Change sync_core() to use MOV to CR2 to serialize Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
[PATCH v2 4/6] x86/paravirt: Make sync_core() be a paravirt op Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
[PATCH v2 3/6] x86/microcode/intel: Replace sync_core() with cpuid_eax(1) Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
[PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-02 12:50 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 18:10 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-02 18:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-02 18:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 18:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-02 19:50 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 20:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-02 21:10 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 18:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@kernel.org> - 2016-12-02 18:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@kernel.org> - 2016-12-02 19:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 19:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@kernel.org> - 2016-12-02 20:00 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 20:10 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 20:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@alien8.de> - 2016-12-02 20:30 +0100
[PATCH] x86/alternatives: Do not use sync_core() to serialize I$ Borislav Petkov <bp@alien8.de> - 2016-12-03 16:10 +0100
Re: [PATCH] x86/alternatives: Do not use sync_core() to serialize I$ Andy Lutomirski <luto@amacapital.net> - 2016-12-03 18:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 20:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 21:50 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 22:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-03 00:00 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-03 00:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 20:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Andy Lutomirski <luto@amacapital.net> - 2016-12-02 20:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@alien8.de> - 2016-12-02 20:40 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@alien8.de> - 2016-12-02 20:30 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-02 19:20 +0100
Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation Borislav Petkov <bp@alien8.de> - 2016-12-03 13:50 +0100
[PATCH v2 2/6] Revert "x86/boot: Fail the boot if !M486 and CPUID is missing" Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
Re: [PATCH 0/4] CPUID-less CPU fixes and improvements Andy Lutomirski <luto@amacapital.net> - 2016-12-02 01:40 +0100
Re: [PATCH 0/4] CPUID-less CPU fixes and improvements Ingo Molnar <mingo@kernel.org> - 2016-12-02 11:20 +0100
[PATCH v2 0/6] CPUID-less CPU/sync_core fixes and improvements Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
[PATCH v2 1/6] x86/asm/32: Make sync_core() handle missing CPUID on all 32-bit kernels Andy Lutomirski <luto@kernel.org> - 2016-12-02 01:40 +0100
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