On 04/05/2010 01:30 PM, Ky Srinivasan wrote:
> +static cycle_t read_hv_clock(struct clocksource *arg)
> +{
> + cycle_t current_tick;
> + /*
> + * Read the partition counter to get the current tick count. This count
> + * is set to 0 when the partition is created and is incremented in
> + * 100 nanosecond units.
> + */
> + rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> + return current_tick;
> +}
> +
> +static struct clocksource clocksource_hyperv = {
> + .name = "hyperv_clocksource",
>
Seems like a redundantly long name; any use of this string is going to
be in a context where it is obviously a clocksource. How about just
"hyperv"?
> + .rating = 400, /* use this when running on Hyperv*/
> + .read = read_hv_clock,
> + .mask = CLOCKSOURCE_MASK(64),
> + .shift = HV_CLOCK_SHIFT,
> +};
> +
> +static struct dmi_system_id __initconst
> +hv_timesource_dmi_table[] __maybe_unused = {
> + {
> + .ident = "Hyper-V",
> + .matches = {
> + DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
> + DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
> + DMI_MATCH(DMI_BOARD_NAME, "Virtual Machine"),
> + },
> + },
> + { },
> +};
> +MODULE_DEVICE_TABLE(dmi, hv_timesource_dmi_table);
>
So you use the DMI signatures to determine whether the module is needed,
but cpuid to work out if the feature is present?
> +
> +static struct pci_device_id __initconst
> +hv_timesource_pci_table[] __maybe_unused = {
> + { PCI_DEVICE(0x1414, 0x5353) }, /* VGA compatible controller */
> + { 0 }
> +};
> +MODULE_DEVICE_TABLE(pci, hv_timesource_pci_table);
>
And/or PCI?
Seems a bit... ad-hoc? Is this the official way to determine the
presence of Hyper-V?
> +
> +
> +static int __init hv_detect_hyperv(void)
>
This looks generally useful. Should it be hidden away in the
clocksource driver, or in some common hyper-v code? Do other hyper-v
drivers have versions of this?
> +{
> + u32 eax, ebx, ecx, edx;
> + static char hyp_signature[20];
>
20? static?
> +
> + cpuid(1,&eax,&ebx,&ecx,&edx);
> + if (!(ecx& HV_HYPERVISOR_PRESENT_BIT)) {
> + printk(KERN_WARNING
> + "Not on a Hypervisor\n");
>
This just looks like noise, especially since it doesn't identify what is
generating the message. And if you compile this code in as =y
(non-modular) then it will complain every boot.
> + return 1;
> + }
> + cpuid(HV_CPUID_SIGNATURE,&eax,&ebx,&ecx,&edx);
> + *(u32 *)(hyp_signature + 0) = ebx;
> + *(u32 *)(hyp_signature + 4) = ecx;
> + *(u32 *)(hyp_signature + 8) = edx;
> + hyp_signature[12] = 0;
> +
> + if ((eax< HV_CPUID_MIN) || (strcmp("Microsoft Hv", hyp_signature))) {
>
memcmp, surely?
> + printk(KERN_WARNING
> + "Not on HyperV; signature %s, eax %x\n",
> + hyp_signature, eax);
> + return 1;
> + }
> + /*
> + * Extract the features, recommendations etc.
> + */
> + cpuid(HV_CPUID_FEATURES,&eax,&ebx,&ecx,&edx);
> + if (!(eax& 0x10)) {
> + printk(KERN_WARNING "HyperV Time Ref Counter not available!\n");
> + return 1;
> + }
> +
> + cpuid(HV_CPUID_RECOMMENDATIONS,&eax,&ebx,&ecx,&edx);
> + printk(KERN_INFO "HyperV recommendations: %x\n", eax);
> + printk(KERN_INFO "HyperV spin count: %x\n", ebx);
> + return 0;
> +}
> +
> +
> +static int __init init_hv_clocksource(void)
> +{
> + if (hv_detect_hyperv())
> + return -ENODEV;
> + /*
> + * The time ref counter in HyperV is in 100ns units.
> + * The definition of mult is:
> + * mult/2^shift = ns/cyc = 100
> + * mult = (100<< shift)
> + */
> + clocksource_hyperv.mult = (100<< HV_CLOCK_SHIFT);
>
Why not initialize this in the structure? It's just 100<<22 isn't it?
> + printk(KERN_INFO "Registering HyperV clock source\n");
> + return clocksource_register(&clocksource_hyperv);
> +}
> +
> +module_init(init_hv_clocksource);
> +MODULE_DESCRIPTION("HyperV based clocksource");
> +MODULE_AUTHOR("K. Y. Srinivasan<ksriniva...@novell.com>");
> +MODULE_LICENSE("GPL");
> Index: linux/drivers/staging/hv/Makefile
> ===================================================================
> --- linux.orig/drivers/staging/hv/Makefile 2010-04-05 13:02:06.000000000
> -0600
> +++ linux/drivers/staging/hv/Makefile 2010-04-05 13:02:13.000000000 -0600
> @@ -1,4 +1,4 @@
> -obj-$(CONFIG_HYPERV) += hv_vmbus.o
> +obj-$(CONFIG_HYPERV) += hv_vmbus.o hv_timesource.o
> obj-$(CONFIG_HYPERV_STORAGE) += hv_storvsc.o
> obj-$(CONFIG_HYPERV_BLOCK) += hv_blkvsc.o
> obj-$(CONFIG_HYPERV_NET) += hv_netvsc.o
>
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