Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-10-09 Thread H. Peter Anvin 
On 09/27/2013 08:35 AM, KY Srinivasan wrote:
 
 Thanks Olaf. Could you submit the patch.
 

Haven't heard anything from Olaf... could you fold in the fix and resumbit?

-hpa


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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-10-09 Thread KY Srinivasan 


 -Original Message-
 From: H. Peter Anvin [mailto:h...@zytor.com]
 Sent: Wednesday, October 09, 2013 3:50 PM
 To: KY Srinivasan
 Cc: Olaf Hering; x...@kernel.org; gre...@linuxfoundation.org; linux-
 ker...@vger.kernel.org; de...@linuxdriverproject.org; a...@canonical.com;
 jasow...@redhat.com; t...@linutronix.de; jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On 09/27/2013 08:35 AM, KY Srinivasan wrote:
 
  Thanks Olaf. Could you submit the patch.
 
 
 Haven't heard anything from Olaf... could you fold in the fix and resumbit?

I think Olaf sent the updated patch out; I will dig up the email and resend it.

Regards,

K. Y
 
   -hpa
 

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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-27 Thread Olaf Hering 
On Tue, Sep 03, K. Y. Srinivasan wrote:

 Hyper-V supports a mechanism for retrieving the local APIC frequency.Use this 
 and bypass
 the calibration code in the kernel. This would allow us to boot the Linux 
 kernel as a
 modern VM on Hyper-V where many of the legacy devices (such as PIT) are not 
 emulated.

 + if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
 + /*
 +  * Get the APIC frequency.
 +  */
 + rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
 + hv_lapic_frequency /= HZ;

This leads to build errors on 32bit:

linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to 
`__udivdi3'

Up to now I have only tested on 64bit, sorry for that.


Olaf
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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-27 Thread Olaf Hering 
On Fri, Sep 27, KY Srinivasan wrote:

  This leads to build errors on 32bit:
  
  linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
  `__udivdi3'
  
  Up to now I have only tested on 64bit, sorry for that.
 
 Thanks Olaf. I am travelling currently; I will fix it when I get back (early 
 next week).

This change seems to fix it:

-+  hv_lapic_frequency /= HZ;
++  div_u64(hv_lapic_frequency, HZ);

Olaf
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-27 Thread KY Srinivasan 


 -Original Message-
 From: Olaf Hering [mailto:o...@aepfle.de]
 Sent: Friday, September 27, 2013 8:33 AM
 To: KY Srinivasan
 Cc: x...@kernel.org; gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
 de...@linuxdriverproject.org; a...@canonical.com; jasow...@redhat.com;
 t...@linutronix.de; h...@zytor.com; jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On Fri, Sep 27, KY Srinivasan wrote:
 
   This leads to build errors on 32bit:
  
   linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
   `__udivdi3'
  
   Up to now I have only tested on 64bit, sorry for that.
 
  Thanks Olaf. I am travelling currently; I will fix it when I get back 
  (early next
 week).
 
 This change seems to fix it:
 
 -+  hv_lapic_frequency /= HZ;
 ++  div_u64(hv_lapic_frequency, HZ);

Thanks Olaf. Could you submit the patch.

Regards,

K. Y
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-27 Thread KY Srinivasan 


 -Original Message-
 From: Olaf Hering [mailto:o...@aepfle.de]
 Sent: Friday, September 27, 2013 8:10 AM
 To: KY Srinivasan
 Cc: x...@kernel.org; gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
 de...@linuxdriverproject.org; a...@canonical.com; jasow...@redhat.com;
 t...@linutronix.de; h...@zytor.com; jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On Tue, Sep 03, K. Y. Srinivasan wrote:
 
  Hyper-V supports a mechanism for retrieving the local APIC frequency.Use 
  this
 and bypass
  the calibration code in the kernel. This would allow us to boot the Linux 
  kernel
 as a
  modern VM on Hyper-V where many of the legacy devices (such as PIT) are
 not emulated.
 
  +   if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
  +   /*
  +* Get the APIC frequency.
  +*/
  +   rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
  +   hv_lapic_frequency /= HZ;
 
 This leads to build errors on 32bit:
 
 linux-3.12-rc2/arch/x86/kernel/cpu/mshyperv.c:88: undefined reference to
 `__udivdi3'
 
 Up to now I have only tested on 64bit, sorry for that.

Thanks Olaf. I am travelling currently; I will fix it when I get back (early 
next week).

K. Y
 
 
 Olaf
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-23 Thread KY Srinivasan 


 -Original Message-
 From: Gleb Natapov [mailto:g...@redhat.com]
 Sent: Tuesday, September 17, 2013 10:44 PM
 To: KY Srinivasan
 Cc: H. Peter Anvin; x...@kernel.org; gre...@linuxfoundation.org; linux-
 ker...@vger.kernel.org; de...@linuxdriverproject.org; o...@aepfle.de;
 a...@canonical.com; jasow...@redhat.com; t...@linutronix.de;
 jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On Tue, Sep 17, 2013 at 07:53:36PM +, KY Srinivasan wrote:
Thanks Gleb. Here is the link for the latest Hyper-V specification:
http://www.microsoft.com/en-us/download/details.aspx?id=39289
   
This spec talks about how migration is handled with regards to TSC.
   
   All I can see is 15.4.3 Partition Reference TSC Mechanism. I see
   nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
   a partition needs AccessFrequencyMsrs privilege, may be partition that
   cab be migrated does not have this privilege?
 
  If you use the MSR to read the TSC frequency, then indeed when you migrate
 then there
  is no guarantee that the TSC frequency won't change when you migrate. The
 approach
  described in section 15.4.3 is the preferred approach that can accommodate
 migration.
 
 Thanks.

Peter,
Please let me know if there are other issues I need to address here. Now that 
Dmitry has queued up the
Hyper-V keyboard driver, with this patch we can fully support Linux on our uefi 
firmware.

Regards,

K. Y 
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-23 Thread KY Srinivasan 


 -Original Message-
 From: H. Peter Anvin [mailto:h...@zytor.com]
 Sent: Monday, September 23, 2013 8:50 AM
 To: KY Srinivasan
 Cc: Gleb Natapov; x...@kernel.org; gre...@linuxfoundation.org; linux-
 ker...@vger.kernel.org; de...@linuxdriverproject.org; o...@aepfle.de;
 a...@canonical.com; jasow...@redhat.com; t...@linutronix.de;
 jbeul...@suse.com; b...@alien8.de; dmitry.torok...@gmail.com
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On 09/23/2013 06:02 AM, KY Srinivasan wrote:
 
  Peter,
  Please let me know if there are other issues I need to address here. Now 
  that
 Dmitry has queued up the
  Hyper-V keyboard driver, with this patch we can fully support Linux on our 
  uefi
 firmware.
 
 
 I just got back from Plumber's -- this is on my short list of things to
 look at.  If you haven't heard anything by Wednesday, ping me.

Thank you.

K. Y

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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-17 Thread Gleb Natapov 
On Fri, Sep 13, 2013 at 02:28:35PM +, KY Srinivasan wrote:
 
 
  -Original Message-
  From: Gleb Natapov [mailto:g...@redhat.com]
  Sent: Friday, September 13, 2013 2:55 AM
  To: KY Srinivasan
  Cc: H. Peter Anvin; x...@kernel.org; gre...@linuxfoundation.org; linux-
  ker...@vger.kernel.org; de...@linuxdriverproject.org; o...@aepfle.de;
  a...@canonical.com; jasow...@redhat.com; t...@linutronix.de;
  jbeul...@suse.com; b...@alien8.de
  Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
  from the hypervisor
  
  On Fri, Sep 13, 2013 at 01:43:09AM +, KY Srinivasan wrote:
  
  
-Original Message-
From: H. Peter Anvin [mailto:h...@zytor.com]
Sent: Thursday, September 12, 2013 5:28 PM
To: KY Srinivasan
Cc: x...@kernel.org; gre...@linuxfoundation.org; linux-
  ker...@vger.kernel.org;
de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
jasow...@redhat.com; t...@linutronix.de; jbeul...@suse.com;
  b...@alien8.de
Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer 
frequency
from the hypervisor
   
On 09/12/2013 05:06 PM, KY Srinivasan wrote:

 Peter,

 Let me know if you want me to address any additional issues in this 
 patch.

   
Please address Jan and Gleb's feedback.
  
   Gleb's feedback was a question and I answered that as I did Jan's 
   feedback as
  well.
   Gleb, Jan, please let me know if there is something else you want 
   addressed
  here.
  
  No, I am just interesting to know some details about the interface since
  I cannot find it documented in Hyper-V spec.
 
 Thanks Gleb. Here is the link for the latest Hyper-V specification:
 http://www.microsoft.com/en-us/download/details.aspx?id=39289
 
 This spec talks about how migration is handled with regards to TSC.
 
All I can see is 15.4.3 Partition Reference TSC Mechanism. I see
nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
a partition needs AccessFrequencyMsrs privilege, may be partition that
cab be migrated does not have this privilege?

--
Gleb.
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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-17 Thread Gleb Natapov 
On Tue, Sep 17, 2013 at 07:53:36PM +, KY Srinivasan wrote:
   Thanks Gleb. Here is the link for the latest Hyper-V specification:
   http://www.microsoft.com/en-us/download/details.aspx?id=39289
  
   This spec talks about how migration is handled with regards to TSC.
  
  All I can see is 15.4.3 Partition Reference TSC Mechanism. I see
  nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR
  a partition needs AccessFrequencyMsrs privilege, may be partition that
  cab be migrated does not have this privilege?
 
 If you use the MSR to read the TSC frequency, then indeed when you migrate 
 then there
 is no guarantee that the TSC frequency won't change when you migrate. The 
 approach
 described in section 15.4.3 is the preferred approach that can accommodate 
 migration.
 
Thanks.

--
Gleb.
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-13 Thread Jan Beulich 
 On 13.09.13 at 03:43, KY Srinivasan k...@microsoft.com wrote:

 
 -Original Message-
 From: H. Peter Anvin [mailto:h...@zytor.com]
 Sent: Thursday, September 12, 2013 5:28 PM
 To: KY Srinivasan
 Cc: x...@kernel.org; gre...@linuxfoundation.org; 
 linux-ker...@vger.kernel.org;
 de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
 jasow...@redhat.com; t...@linutronix.de; jbeul...@suse.com; b...@alien8.de 
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On 09/12/2013 05:06 PM, KY Srinivasan wrote:
 
  Peter,
 
  Let me know if you want me to address any additional issues in this patch.
 
 
 Please address Jan and Gleb's feedback.
 
 Gleb's feedback was a question and I answered that as I did Jan's feedback 
 as well.
 Gleb, Jan, please let me know if there is something else you want addressed 
 here.

Indeed, apart from the question whether to change that one
message's level from KERN_INFO to KERN_DEBUG, there was
nothing really left unexplained (the aspect of the artificial tying
together of distinct features is really something KY has to
decide - I merely tried to point out that this is odd).

Jan

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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-13 Thread Gleb Natapov 
On Fri, Sep 13, 2013 at 01:43:09AM +, KY Srinivasan wrote:
 
 
  -Original Message-
  From: H. Peter Anvin [mailto:h...@zytor.com]
  Sent: Thursday, September 12, 2013 5:28 PM
  To: KY Srinivasan
  Cc: x...@kernel.org; gre...@linuxfoundation.org; 
  linux-ker...@vger.kernel.org;
  de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
  jasow...@redhat.com; t...@linutronix.de; jbeul...@suse.com; b...@alien8.de
  Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
  from the hypervisor
  
  On 09/12/2013 05:06 PM, KY Srinivasan wrote:
  
   Peter,
  
   Let me know if you want me to address any additional issues in this patch.
  
  
  Please address Jan and Gleb's feedback.
 
 Gleb's feedback was a question and I answered that as I did Jan's feedback as 
 well.
 Gleb, Jan, please let me know if there is something else you want addressed 
 here.
 
No, I am just interesting to know some details about the interface since
I cannot find it documented in Hyper-V spec.

--
Gleb.
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-13 Thread KY Srinivasan 


 -Original Message-
 From: Gleb Natapov [mailto:g...@redhat.com]
 Sent: Friday, September 13, 2013 2:55 AM
 To: KY Srinivasan
 Cc: H. Peter Anvin; x...@kernel.org; gre...@linuxfoundation.org; linux-
 ker...@vger.kernel.org; de...@linuxdriverproject.org; o...@aepfle.de;
 a...@canonical.com; jasow...@redhat.com; t...@linutronix.de;
 jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On Fri, Sep 13, 2013 at 01:43:09AM +, KY Srinivasan wrote:
 
 
   -Original Message-
   From: H. Peter Anvin [mailto:h...@zytor.com]
   Sent: Thursday, September 12, 2013 5:28 PM
   To: KY Srinivasan
   Cc: x...@kernel.org; gre...@linuxfoundation.org; linux-
 ker...@vger.kernel.org;
   de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
   jasow...@redhat.com; t...@linutronix.de; jbeul...@suse.com;
 b...@alien8.de
   Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer 
   frequency
   from the hypervisor
  
   On 09/12/2013 05:06 PM, KY Srinivasan wrote:
   
Peter,
   
Let me know if you want me to address any additional issues in this 
patch.
   
  
   Please address Jan and Gleb's feedback.
 
  Gleb's feedback was a question and I answered that as I did Jan's feedback 
  as
 well.
  Gleb, Jan, please let me know if there is something else you want addressed
 here.
 
 No, I am just interesting to know some details about the interface since
 I cannot find it documented in Hyper-V spec.

Thanks Gleb. Here is the link for the latest Hyper-V specification:
http://www.microsoft.com/en-us/download/details.aspx?id=39289

This spec talks about how migration is handled with regards to TSC.

Peter, if you are ok with the message level, there is no other current issue
that is left unaddressed.

Regards,

K. Y 
 
 --
   Gleb.
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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-12 Thread H. Peter Anvin 
On 09/12/2013 05:06 PM, KY Srinivasan wrote:
 
 Peter,
 
 Let me know if you want me to address any additional issues in this patch.
 

Please address Jan and Gleb's feedback.

-hpa


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Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-05 Thread Gleb Natapov 
On Wed, Sep 04, 2013 at 03:16:30PM +, KY Srinivasan wrote:
 
 
  -Original Message-
  From: Gleb Natapov [mailto:g...@redhat.com]
  Sent: Wednesday, September 04, 2013 2:40 AM
  To: KY Srinivasan
  Cc: x...@kernel.org; gre...@linuxfoundation.org; 
  linux-ker...@vger.kernel.org;
  de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
  jasow...@redhat.com; t...@linutronix.de; h...@zytor.com;
  jbeul...@suse.com; b...@alien8.de
  Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
  from the hypervisor
  
  On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
   Hyper-V supports a mechanism for retrieving the local APIC frequency.Use 
   this
  and bypass
   the calibration code in the kernel. This would allow us to boot the Linux 
   kernel
  as a
   modern VM on Hyper-V where many of the legacy devices (such as PIT) are
  not emulated.
  
   I would like to thank Olaf Hering o...@aepfle.de, Jan Beulich
  jbeul...@suse.com and
   H. Peter Anvin h.peter.an...@intel.com for their help in this effort.
  
   In this version of the patch, I have addressed Jan's comments.
  
   Signed-off-by: K. Y. Srinivasan k...@microsoft.com
   ---
arch/x86/include/uapi/asm/hyperv.h |   19 +++
arch/x86/kernel/cpu/mshyperv.c |   24 
2 files changed, 43 insertions(+), 0 deletions(-)
  
   diff --git a/arch/x86/include/uapi/asm/hyperv.h
  b/arch/x86/include/uapi/asm/hyperv.h
   index b80420b..b8f1c01 100644
   --- a/arch/x86/include/uapi/asm/hyperv.h
   +++ b/arch/x86/include/uapi/asm/hyperv.h
   @@ -27,6 +27,19 @@
#define HV_X64_MSR_VP_RUNTIME_AVAILABLE  (1  0)
/* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
#define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE  (1  1)
   +
   +/*
   + * There is a single feature flag that signifies the presence of the MSR
   + * that can be used to retrieve both the local APIC Timer frequency as
   + * well as the TSC frequency.
   + */
   +
   +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is
  available */
   +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
   +
   +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
   +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)
   +
/*
 * Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
 * and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
   @@ -136,6 +149,12 @@
/* MSR used to read the per-partition time reference counter */
#define HV_X64_MSR_TIME_REF_COUNT0x4020
  
   +/* MSR used to retrieve the TSC frequency */
   +#define HV_X64_MSR_TSC_FREQUENCY 0x4022
   +
  You do not use this MSR in the patch, but in general how it suppose to
  work during migration if host TSC frequency changes?
 
 TSC related migration issues are distinct from how we calibrate the TSC 
 frequency. This MSR
 allows you to retrieve the TSC frequency without having to do explicit 
 calibration.
 
But the value retrieved can be obsolete by the time guest sues it due to
migration.

 To address the migration issues; the hypervisor provides additional 
 information on the host
 that you are running that can be used to compensate for differences in TSC 
 across hosts.  
 
Are you referring to Reference TSC Page here?

--
Gleb.
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-04 Thread KY Srinivasan 


 -Original Message-
 From: Gleb Natapov [mailto:g...@redhat.com]
 Sent: Wednesday, September 04, 2013 2:40 AM
 To: KY Srinivasan
 Cc: x...@kernel.org; gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
 de...@linuxdriverproject.org; o...@aepfle.de; a...@canonical.com;
 jasow...@redhat.com; t...@linutronix.de; h...@zytor.com;
 jbeul...@suse.com; b...@alien8.de
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
 On Tue, Sep 03, 2013 at 11:30:23AM -0700, K. Y. Srinivasan wrote:
  Hyper-V supports a mechanism for retrieving the local APIC frequency.Use 
  this
 and bypass
  the calibration code in the kernel. This would allow us to boot the Linux 
  kernel
 as a
  modern VM on Hyper-V where many of the legacy devices (such as PIT) are
 not emulated.
 
  I would like to thank Olaf Hering o...@aepfle.de, Jan Beulich
 jbeul...@suse.com and
  H. Peter Anvin h.peter.an...@intel.com for their help in this effort.
 
  In this version of the patch, I have addressed Jan's comments.
 
  Signed-off-by: K. Y. Srinivasan k...@microsoft.com
  ---
   arch/x86/include/uapi/asm/hyperv.h |   19 +++
   arch/x86/kernel/cpu/mshyperv.c |   24 
   2 files changed, 43 insertions(+), 0 deletions(-)
 
  diff --git a/arch/x86/include/uapi/asm/hyperv.h
 b/arch/x86/include/uapi/asm/hyperv.h
  index b80420b..b8f1c01 100644
  --- a/arch/x86/include/uapi/asm/hyperv.h
  +++ b/arch/x86/include/uapi/asm/hyperv.h
  @@ -27,6 +27,19 @@
   #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1  0)
   /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
   #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1  1)
  +
  +/*
  + * There is a single feature flag that signifies the presence of the MSR
  + * that can be used to retrieve both the local APIC Timer frequency as
  + * well as the TSC frequency.
  + */
  +
  +/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is
 available */
  +#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
  +
  +/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
  +#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)
  +
   /*
* Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
* and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
  @@ -136,6 +149,12 @@
   /* MSR used to read the per-partition time reference counter */
   #define HV_X64_MSR_TIME_REF_COUNT  0x4020
 
  +/* MSR used to retrieve the TSC frequency */
  +#define HV_X64_MSR_TSC_FREQUENCY   0x4022
  +
 You do not use this MSR in the patch, but in general how it suppose to
 work during migration if host TSC frequency changes?

TSC related migration issues are distinct from how we calibrate the TSC 
frequency. This MSR
allows you to retrieve the TSC frequency without having to do explicit 
calibration.

To address the migration issues; the hypervisor provides additional information 
on the host
that you are running that can be used to compensate for differences in TSC 
across hosts.  

Regards,

K. Y
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RE: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-04 Thread KY Srinivasan 


 -Original Message-
 From: Jan Beulich [mailto:jbeul...@suse.com]
 Sent: Wednesday, September 04, 2013 12:17 AM
 To: KY Srinivasan
 Cc: o...@aepfle.de; b...@alien8.de; a...@canonical.com; x...@kernel.org;
 t...@linutronix.de; de...@linuxdriverproject.org; gre...@linuxfoundation.org;
 jasow...@redhat.com; linux-ker...@vger.kernel.org; h...@zytor.com
 Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency
 from the hypervisor
 
  On 03.09.13 at 20:30, K. Y. Srinivasan k...@microsoft.com wrote:
  @@ -76,6 +80,26 @@ static void __init ms_hyperv_init_platform(void)
  printk(KERN_INFO HyperV: features 0x%x, hints 0x%x\n,
 ms_hyperv.features, ms_hyperv.hints);
 
  +   if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
  +   /*
  +* Get the APIC frequency.
  +*/
  +   rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
  +   hv_lapic_frequency /= HZ;
  +   lapic_timer_frequency = hv_lapic_frequency;
  +   printk(KERN_INFO HyperV: LAPIC Timer Frequency: %#x\n,
  +   lapic_timer_frequency);
  +
  +   /*
  +* On Hyper-V, when we are booting off an EFI firmware stack,
  +* we do not have many legacy devices including PIC, PIT etc.
  +*/
  +   if (efi_enabled(EFI_BOOT)) {
  +   printk(KERN_INFO HyperV: Using null_legacy_pic\n);
  +   legacy_pic = null_legacy_pic;
  +   }
 
 And this check is really connected to the feature check around the
 whole block, rather than being independent? (I'd also think that
 this latter message would suffice to be KERN_DEBUG).

I felt it was safer to first check for the feature  since if the feature is not
there, we need to calibrate based on PIT. Furthermore, the feature is available
even in legacy environments when we are not booting on an EFI stack.

Regards,

K. Y

 
 Jan

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[PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor

2013-09-03 Thread K. Y. Srinivasan 
Hyper-V supports a mechanism for retrieving the local APIC frequency.Use this 
and bypass
the calibration code in the kernel. This would allow us to boot the Linux 
kernel as a
modern VM on Hyper-V where many of the legacy devices (such as PIT) are not 
emulated.

I would like to thank Olaf Hering o...@aepfle.de, Jan Beulich 
jbeul...@suse.com and
H. Peter Anvin h.peter.an...@intel.com for their help in this effort.

In this version of the patch, I have addressed Jan's comments.

Signed-off-by: K. Y. Srinivasan k...@microsoft.com
---
 arch/x86/include/uapi/asm/hyperv.h |   19 +++
 arch/x86/kernel/cpu/mshyperv.c |   24 
 2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/uapi/asm/hyperv.h 
b/arch/x86/include/uapi/asm/hyperv.h
index b80420b..b8f1c01 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -27,6 +27,19 @@
 #define HV_X64_MSR_VP_RUNTIME_AVAILABLE(1  0)
 /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
 #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE(1  1)
+
+/*
+ * There is a single feature flag that signifies the presence of the MSR
+ * that can be used to retrieve both the local APIC Timer frequency as
+ * well as the TSC frequency.
+ */
+
+/* Local APIC timer frequency MSR (HV_X64_MSR_APIC_FREQUENCY) is available */
+#define HV_X64_MSR_APIC_FREQUENCY_AVAILABLE (1  11)
+
+/* TSC frequency MSR (HV_X64_MSR_TSC_FREQUENCY) is available */
+#define HV_X64_MSR_TSC_FREQUENCY_AVAILABLE (1  11)
+
 /*
  * Basic SynIC MSRs (HV_X64_MSR_SCONTROL through HV_X64_MSR_EOM
  * and HV_X64_MSR_SINT0 through HV_X64_MSR_SINT15) available
@@ -136,6 +149,12 @@
 /* MSR used to read the per-partition time reference counter */
 #define HV_X64_MSR_TIME_REF_COUNT  0x4020
 
+/* MSR used to retrieve the TSC frequency */
+#define HV_X64_MSR_TSC_FREQUENCY   0x4022
+
+/* MSR used to retrieve the local APIC timer frequency */
+#define HV_X64_MSR_APIC_FREQUENCY  0x4023
+
 /* Define the virtual APIC registers */
 #define HV_X64_MSR_EOI 0x4070
 #define HV_X64_MSR_ICR 0x4071
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 71a39f3..b3dc639 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -15,6 +15,7 @@
 #include linux/clocksource.h
 #include linux/module.h
 #include linux/hardirq.h
+#include linux/efi.h
 #include linux/interrupt.h
 #include asm/processor.h
 #include asm/hypervisor.h
@@ -23,6 +24,7 @@
 #include asm/desc.h
 #include asm/idle.h
 #include asm/irq_regs.h
+#include asm/i8259.h
 
 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -67,6 +69,8 @@ static struct clocksource hyperv_cs = {
 
 static void __init ms_hyperv_init_platform(void)
 {
+   u64 hv_lapic_frequency;
+
/*
 * Extract the features and hints
 */
@@ -76,6 +80,26 @@ static void __init ms_hyperv_init_platform(void)
printk(KERN_INFO HyperV: features 0x%x, hints 0x%x\n,
   ms_hyperv.features, ms_hyperv.hints);
 
+   if (ms_hyperv.features  HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
+   /*
+* Get the APIC frequency.
+*/
+   rdmsrl(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
+   hv_lapic_frequency /= HZ;
+   lapic_timer_frequency = hv_lapic_frequency;
+   printk(KERN_INFO HyperV: LAPIC Timer Frequency: %#x\n,
+   lapic_timer_frequency);
+
+   /*
+* On Hyper-V, when we are booting off an EFI firmware stack,
+* we do not have many legacy devices including PIC, PIT etc.
+*/
+   if (efi_enabled(EFI_BOOT)) {
+   printk(KERN_INFO HyperV: Using null_legacy_pic\n);
+   legacy_pic = null_legacy_pic;
+   }
+   }
+
if (ms_hyperv.features  HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
clocksource_register_hz(hyperv_cs, NSEC_PER_SEC/100);
 }
-- 
1.7.4.1

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