Re: [PATCH v1 6/9] KVM: x86: Add Heki hypervisor support

[Wei Liu <wei.liu@kernel.org>]

On Fri, May 05, 2023 at 05:20:43PM +0200, Mickaël Salaün wrote:
> From: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
> 
> Each supported hypervisor in x86 implements a struct x86_hyper_init to
> define the init functions for the hypervisor.  Define a new init_heki()
> entry point in struct x86_hyper_init.  Hypervisors that support Heki
> must define this init_heki() function.  Call init_heki() of the chosen
> hypervisor in init_hypervisor_platform().
> 
> Create a heki_hypervisor structure that each hypervisor can fill
> with its data and functions. This will allow the Heki feature to work
> in a hypervisor agnostic way.
> 
> Declare and initialize a "heki_hypervisor" structure for KVM so KVM can
> support Heki.  Define the init_heki() function for KVM.  In init_heki(),
> set the hypervisor field in the generic "heki" structure to the KVM
> "heki_hypervisor".  After this point, generic Heki code can access the
> KVM Heki data and functions.
> 
[...]
> +static void kvm_init_heki(void)
> +{
> +	long err;
> +
> +	if (!kvm_para_available())
> +		/* Cannot make KVM hypercalls. */
> +		return;
> +
> +	err = kvm_hypercall3(KVM_HC_LOCK_MEM_PAGE_RANGES, -1, -1, -1);

Why not do a proper version check or capability check here? If the ABI
or supported features ever change then we have something to rely on?

Thanks,
Wei.