Re: [PATCH v14 02/21] KVM: Rename CONFIG_KVM_GENERIC_PRIVATE_MEM to CONFIG_KVM_GENERIC_GMEM_POPULATE

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 7/15/2025 5:33 PM, Fuad Tabba wrote:
> The original name was vague regarding its functionality. This Kconfig
> option specifically enables and gates the kvm_gmem_populate() function,
> which is responsible for populating a GPA range with guest data.

Well, I disagree.

The config KVM_GENERIC_PRIVATE_MEM was introduced by commit 89ea60c2c7b5 
("KVM: x86: Add support for "protected VMs" that can utilize private 
memory"), which is a convenient config for vm types that requires 
private memory support, e.g., SNP, TDX, and KVM_X86_SW_PROTECTED_VM.

It was commit e4ee54479273 ("KVM: guest_memfd: let kvm_gmem_populate() 
operate only on private gfns") that started to use 
CONFIG_KVM_GENERIC_PRIVATE_MEM gates kvm_gmem_populate() function. But 
CONFIG_KVM_GENERIC_PRIVATE_MEM is not for kvm_gmem_populate() only.

If using CONFIG_KVM_GENERIC_PRIVATE_MEM to gate kvm_gmem_populate() is 
vague and confusing, we can introduce KVM_GENERIC_GMEM_POPULATE to gate 
kvm_gmem_populate() and select KVM_GENERIC_GMEM_POPULATE under 
CONFIG_KVM_GENERIC_PRIVATE_MEM.

Directly replace CONFIG_KVM_GENERIC_PRIVATE_MEM with 
KVM_GENERIC_GMEM_POPULATE doesn't look correct to me.

> The new name, KVM_GENERIC_GMEM_POPULATE, describes the purpose of the
> option: to enable generic guest_memfd population mechanisms. This
> improves clarity for developers and ensures the name accurately reflects
> the functionality it controls, especially as guest_memfd support expands
> beyond purely "private" memory scenarios.
> 
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Reviewed-by: Shivank Garg <shivankg@amd.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> Co-developed-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>   arch/x86/kvm/Kconfig     | 6 +++---
>   include/linux/kvm_host.h | 2 +-
>   virt/kvm/Kconfig         | 2 +-
>   virt/kvm/guest_memfd.c   | 2 +-
>   4 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 2eeffcec5382..df1fdbb4024b 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -46,7 +46,7 @@ config KVM_X86
>   	select HAVE_KVM_PM_NOTIFIER if PM
>   	select KVM_GENERIC_HARDWARE_ENABLING
>   	select KVM_GENERIC_PRE_FAULT_MEMORY
> -	select KVM_GENERIC_PRIVATE_MEM if KVM_SW_PROTECTED_VM
> +	select KVM_GENERIC_GMEM_POPULATE if KVM_SW_PROTECTED_VM
>   	select KVM_WERROR if WERROR
>   
>   config KVM
> @@ -95,7 +95,7 @@ config KVM_SW_PROTECTED_VM
>   config KVM_INTEL
>   	tristate "KVM for Intel (and compatible) processors support"
>   	depends on KVM && IA32_FEAT_CTL
> -	select KVM_GENERIC_PRIVATE_MEM if INTEL_TDX_HOST
> +	select KVM_GENERIC_GMEM_POPULATE if INTEL_TDX_HOST
>   	select KVM_GENERIC_MEMORY_ATTRIBUTES if INTEL_TDX_HOST
>   	help
>   	  Provides support for KVM on processors equipped with Intel's VT
> @@ -157,7 +157,7 @@ config KVM_AMD_SEV
>   	depends on KVM_AMD && X86_64
>   	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
>   	select ARCH_HAS_CC_PLATFORM
> -	select KVM_GENERIC_PRIVATE_MEM
> +	select KVM_GENERIC_GMEM_POPULATE
>   	select HAVE_KVM_ARCH_GMEM_PREPARE
>   	select HAVE_KVM_ARCH_GMEM_INVALIDATE
>   	help
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 755b09dcafce..359baaae5e9f 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2556,7 +2556,7 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
>   int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order);
>   #endif
>   
> -#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
> +#ifdef CONFIG_KVM_GENERIC_GMEM_POPULATE
>   /**
>    * kvm_gmem_populate() - Populate/prepare a GPA range with guest data
>    *
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 49df4e32bff7..559c93ad90be 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -116,7 +116,7 @@ config KVM_GMEM
>          select XARRAY_MULTI
>          bool
>   
> -config KVM_GENERIC_PRIVATE_MEM
> +config KVM_GENERIC_GMEM_POPULATE
>          select KVM_GENERIC_MEMORY_ATTRIBUTES
>          select KVM_GMEM
>          bool
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index b2aa6bf24d3a..befea51bbc75 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -638,7 +638,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
>   }
>   EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
>   
> -#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
> +#ifdef CONFIG_KVM_GENERIC_GMEM_POPULATE
>   long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long npages,
>   		       kvm_gmem_populate_cb post_populate, void *opaque)
>   {