linux-kernel - RE: [PATCH char-misc 1/2] Drivers: hv: vmbus: Remove x86 MSR refs in arch independent code

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Date:   Sat, 12 May 2018 12:55:41 +0000
From:   "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>
To:     KY Srinivasan <kys@...rosoft.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "leann.ogasawara@...onical.com" <leann.ogasawara@...onical.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: RE: [PATCH char-misc 1/2] Drivers: hv: vmbus: Remove x86 MSR refs in
 arch independent code

> > -#define hv_init_timer(timer, tick) wrmsrl(timer, tick)
> > -#define hv_init_timer_config(config, val) wrmsrl(config, val)
> > +#define hv_init_timer(timer, tick) \
> > +	wrmsrl(HV_X64_MSR_STIMER0_COUNT + (2*timer), tick)
> > +#define hv_init_timer_config(timer, val) \
> > +	wrmsrl(HV_X64_MSR_STIMER0_CONFIG + (2*timer), val)
>
> Why are we stepping in units of 2?
> 
> K. Y

The register addresses for  the *_CONFIG and *_COUNT registers
are interleaved.  From hyperv-tlfs.h:

#define HV_X64_MSR_STIMER0_CONFIG               0x400000B0
#define HV_X64_MSR_STIMER0_COUNT                0x400000B1
#define HV_X64_MSR_STIMER1_CONFIG               0x400000B2
#define HV_X64_MSR_STIMER1_COUNT                0x400000B3
#define HV_X64_MSR_STIMER2_CONFIG               0x400000B4
#define HV_X64_MSR_STIMER2_COUNT                0x400000B5
#define HV_X64_MSR_STIMER3_CONFIG               0x400000B6
#define HV_X64_MSR_STIMER3_COUNT                0x400000B7

Michael