Re: [dpdk-dev] [PATCH] eal/x86: get hypervisor name

[Thomas Monjalon <thomas@monjalon.net>]

01/12/2017 09:12, Jerin Jacob:
> -----Original Message-----
> > Date: Thu, 30 Nov 2017 22:47:20 +0100
> > From: Thomas Monjalon <thomas@monjalon.net>
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] [PATCH] eal/x86: get hypervisor name
> > X-Mailer: git-send-email 2.15.0
> > 
> > The CPUID instruction is catched by hypervisor which can return
> > a flag indicating one is running, and its name.
> > 
> > Suggested-by: Stephen Hemminger <sthemmin@microsoft.com>
> > Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> > ---
> > warning: to be tested
> > ---
> >  lib/librte_eal/common/arch/arm/rte_cpuflags.c      |  6 +++++
> >  lib/librte_eal/common/arch/ppc_64/rte_cpuflags.c   |  6 +++++
> >  lib/librte_eal/common/arch/x86/rte_cpuflags.c      | 30 ++++++++++++++++++++++
> >  .../common/include/arch/x86/rte_cpuflags.h         |  1 +
> >  .../common/include/generic/rte_cpuflags.h          | 14 ++++++++++
> >  lib/librte_eal/rte_eal_version.map                 |  9 ++++++-
> >  6 files changed, 65 insertions(+), 1 deletion(-)
> >  	RTE_CPUFLAG_FPU,                    /**< FPU */
> > diff --git a/lib/librte_eal/common/include/generic/rte_cpuflags.h b/lib/librte_eal/common/include/generic/rte_cpuflags.h
> > index c1c5551fc..3832fb851 100644
> > --- a/lib/librte_eal/common/include/generic/rte_cpuflags.h
> > +++ b/lib/librte_eal/common/include/generic/rte_cpuflags.h
> > @@ -93,4 +93,18 @@ rte_cpu_check_supported(void);
> >  int
> >  rte_cpu_is_supported(void);
> >  
> > +enum rte_hypervisor {
> > +	RTE_HYPERVISOR_NONE,
> > +	RTE_HYPERVISOR_KVM,
> > +	RTE_HYPERVISOR_HYPERV,
> > +	RTE_HYPERVISOR_VMWARE,
> > +	RTE_HYPERVISOR_UNKNOWN
> > +};
> > +
> > +/**
> > + * Get the type of hypervisor it is running on.
> > + */
> > +enum rte_hypervisor
> > +rte_hypervisor_get_name(void);
> 
> Cc: chaozhu@linux.vnet.ibm.com
> 
> IMO, cpu_flag area is the not the correct abstraction to get
> the hypervisor name. It is x86 specific. I think, correct
> usage will be to call hypervisor specific APIs like KVM_GET_API_VERSION
> https://lwn.net/Articles/658511/

I think it is quite logical because the CPU is virtualized by the hypervisor.
It is similar to get the CPU model, but for a different ring level.

> BTW, What is the need for an DPDK application to know the 
> hypervisor name? What action an DPDK application should
> take based on hypervisor name? if is not interest of data plane
> application why it needs to be abstracted in DPDK?

I see two usages for now.
We can automate the use of the specific VMware TSC (it is an option currently).
We can adapt the device management policy on Hyper-V without waiting a device scan.