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Groups > linux.kernel > #1535186
| From | Boris Ostrovsky <boris.ostrovsky@oracle.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 5/6] x86/xen: Add a Xen-specific sync_core() implementation |
| Date | 2016-12-02 21:10 +0100 |
| Message-ID | <sK2jD-8pR-9@gated-at.bofh.it> (permalink) |
| References | <sJK3o-4BW-19@gated-at.bofh.it> <sJK3n-4BW-9@gated-at.bofh.it> <sJUvM-3hJ-31@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 12/02/2016 06:44 AM, Andrew Cooper wrote: > On 02/12/16 00:35, Andy Lutomirski wrote: >> On Xen PV, CPUID is likely to trap, and Xen hypercalls aren't >> guaranteed to serialize. (Even CPUID isn't *really* guaranteed to >> serialize on Xen PV, but, in practice, any trap it generates will >> serialize.) > Well, Xen will enabled CPUID Faulting wherever it can, which is > realistically all IvyBridge hardware and newer. > > All hypercalls are a privilege change to cpl0. I'd hope this condition > is serialising, but I can't actually find any documentation proving or > disproving this. > >> On my laptop, CPUID(eax=1, ecx=0) is ~83ns and IRET-to-self is >> ~110ns. But Xen PV will trap CPUID if possible, so IRET-to-self >> should end up being a nice speedup. >> >> Cc: Andrew Cooper <andrew.cooper3@citrix.com> >> Signed-off-by: Andy Lutomirski <luto@kernel.org> Executing CPUID in an HVM guest is quite expensive since it will cause a VMEXIT. (And that should be true for any hypervisor, at least on Intel. On AMD it's configurable) -boris
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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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