Alok Kataria wrote:

quoted text
> From: Alok N Kataria

>

> This patch proposes to use a cpuid interface to detect if we are running on an

> hypervisor.

> The discovery of a hypervisor is determined by bit 31 of CPUID#1_ECX, which is

> defined to be "hypervisor present bit". For a VM, the bit is 1, otherwise it is

> set to 0. This bit is not officially documented by either Intel/AMD yet, but

> they plan to do so some time soon, in the meanwhile they have promised to keep

> it reserved for virtualization.

>

> Also, Intel & AMD have reserved the cpuid levels 0x40000000 - 0x400000FF for

> software use. Hypervisors can use these levels to provide an interface to pass

> information from the hypervisor to the guest. This is similar to how we extract

> information about a physical cpu by using cpuid.

> XEN/KVM are already using the info leaf to get the hypervisor signature.

>

> VMware hardware version 7 defines some of these cpuid levels, below is a brief

> description about those. These levels can be implemented by other hypervisors

> too so that Linux has a standard way of communicating to any hypervisor.

>

> Leaf 0x40000000, Hypervisor CPUID information

> # EAX: The maximum input value for hypervisor CPUID info (0x40000010).

> # EBX, ECX, EDX: Hypervisor vendor ID signature. E.g. "VMwareVMware"

> 

This is great, obviously... although we'll have to deal with legacy

methods for a while if not indefinitely (just as we have to for

pre-CPUID processors).
>

quoted text
> +static void __init detect_hypervisor(void)

> +{

> +	if (cpu_has_hypervisor) {

> +		unsigned int eax, ebx, ecx, edx;

> +		char hyper_vendor_id[13];

> +

> +		cpuid(HYPERVISOR_INFO_LEAF, &eax, &ebx, &ecx, &edx);

> +		memcpy(hyper_vendor_id + 0, &ebx, 4);

> +		memcpy(hyper_vendor_id + 4, &ecx, 4);

> +		memcpy(hyper_vendor_id + 8, &edx, 4);

> +		hyper_vendor_id[12] = '__PLACEHOLDER__1_';

> +		printk(KERN_INFO "Hypervisor vendor id %s\n", hyper_vendor_id);

> +	}

> +}

> +

This should be broken out into a separate file in cpu/*, because we

*will* need to detect hypervisors by other means.

quoted text
> --- a/arch/x86/kernel/tsc.c

> +++ b/arch/x86/kernel/tsc.c

> @@ -345,16 +345,38 @@ failed:

>  	return 0;

>  }

>

> +unsigned long hypervisor_tsc_freq(void)

> +{

> +	unsigned long tsc_khz;

> +	unsigned int max_cpuid_leaf;

> +

> +	if (cpu_has_hypervisor) {

> +		max_cpuid_leaf = cpuid_eax(HYPERVISOR_INFO_LEAF);

> +		if (max_cpuid_leaf >= HYPERVISOR_TIMING_LEAF) {

> +			tsc_khz = cpuid_eax(HYPERVISOR_TIMING_LEAF);

> +			printk(KERN_INFO

> +				"TSC frequency read from hypervisor\n");

> +			return tsc_khz;

> +		}

> +	}

> +	return 0;

> +}

> +

I would call this "vmware_tsc_freq()" because it is a VMWare-defined

interface... you can't just poke at 0x40000010 and assume it is using

the VMWare definition.
In order for *that* to be safe, you'd have to have well-defined ranges

for different virtualization vendors where each of them can define their

own stuff.
> diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h

quoted text
> index ee7cbb3..70ca49b 100644

> --- a/include/asm-x86/processor.h

> +++ b/include/asm-x86/processor.h

> @@ -124,6 +124,27 @@ struct cpuinfo_x86 {

>  #define X86_VENDOR_UNKNOWN	0xff

>

>  /*

> + * Intel & AMD have reserved the cpuid levels 0x40000000 - 0x400000FF for

> + * software use. Hypervisors can use these levels to provide an interface

> + * to pass information from the hypervisor to the guest. This is similar

> + * to how we extract information about a physical cpu by using cpuid.

> + */

> +

> +/*

> + * This CPUID leaf returns the information about the hypervisor.

> + * EAX : maximum input value for CPUID supported by the hypervisor.

> + * EBX, ECX, EDX : Hypervisor vendor ID signature. E.g. VMwareVMware.

> + */

> +#define HYPERVISOR_INFO_LEAF   0x40000000

> +/*

> + * This leaf gets timing information from the hypervisor.

> + * EAX: (Virtual) TSC frequency in kHz.

> + * EBX: (Virtual) Bus (local apic timer) frequency in kHz.

> + * ECX, EDX: RESERVED

> + */

> +#define HYPERVISOR_TIMING_LEAF 0x40000010

> +

 is the wrong place for this, and these constants

should have CPUID_ in them to tell what they fundamentally are.
My preference would be for , but otherwise

 wouldn't be entirely wrong.
	-hpa

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