[PATCH v4 01/14] KVM: Allow architectures to disallow pre-fault

[Sean Christopherson]

On Wed, Sep 23, 2026, Lorenzo Stoakes (ARM) wrote:
> All existing architectures which implement KVM pre-fault (x86, s390) have
> mechanisms for disallowing pre-faulting.
> 
> Currently these are open coded as part of kvm_arch_vcpu_pre_fault_memory().
> 
> Formalise this by moving them into a new kvm_arch_pre_fault_allowed() hook,
> which every architecture selecting CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY must
> implement, returning an error code if the operation is disallowed or 0
> otherwise.
> 
> The hook is called early in the generic code, allowing architectures to
> disallow the operation prior to vCPU load.
> 
> This is important, as kvm_vcpu_pre_fault_memory() is the only place where
> generic code can call vcpu_load() on a vCPU that has not yet been
> initialised.
> 
> This lays the foundation for a future change which implements pre-faulting
> for arm64 which needs to disallow the mechanism for uninitialised vCPUs.
> 
> Suggested-by: Oliver Upton <oupton at kernel.org>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>
> ---

Acked-by: Sean Christopherson <seanjc at google.com>