Re: [RFC PATCH 1/1] platform-msi: Add platform check for subdevice irq domain

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi David,

On 12/10/20 4:22 PM, David Woodhouse wrote:
> On Thu, 2020-12-10 at 08:46 +0800, Lu Baolu wrote:
>> +/*
>> + * We want to figure out which context we are running in. But the hardware
>> + * does not introduce a reliable way (instruction, CPUID leaf, MSR, whatever)
>> + * which can be manipulated by the VMM to let the OS figure out where it runs.
>> + * So we go with the below probably_on_bare_metal() function as a replacement
>> + * for definitely_on_bare_metal() to go forward only for the very simple reason
>> + * that this is the only option we have.
>> + */
>> +static const char * const possible_vmm_vendor_name[] = {
>> +       "QEMU", "Bochs", "KVM", "Xen", "VMware", "VMW", "VMware Inc.",
>> +       "innotek GmbH", "Oracle Corporation", "Parallels", "BHYVE",
>> +       "Microsoft Corporation"
>> +};
> 
> People do use SeaBIOS ("Bochs") on bare metal.

Is there any unique way to distinguish between running on bare metal and
VM?

> 
> You'll also see "Amazon EC2" on virt instances as well as bare metal
> instances. Although in that case I believe the virt instances do have
> the 'virtual machine' flag set in bit 4 of the BIOS Characteristics
> Extension Byte 2, and the bare metal obviously don't.
> 

So for Amazon EC2 case, we can use this byte to distinguish. Can you
please point me to the references of this Extension Byte (reference
code/spec or anything else) ?

Best regards,
baolu