Hi Xiaoyao,
On Wed, 16 Jul 2025 at 05:09, Xiaoyao Li <xiaoyao.li@xxxxxxxxx> wrote:
>
> 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.
I'll quote David's reply to an earlier version of this patch [*]:
> > I'm curious what generic means in this name?
>
> That an architecture wants to use the generic version and not provide
> it's own alternative implementation.
>
> We frequently use that term in this context, see GENERIC_IOREMAP as one
> example.
[*] https://lore.kernel.org/all/b6355951-5f9d-4ca9-850f-79e767d8caa2@xxxxxxxxxx/
Thanks,
/fuad
> > 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@xxxxxxxxx>
> > Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
> > Reviewed-by: Shivank Garg <shivankg@xxxxxxx>
> > Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Co-developed-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
> > ---
> > 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)
> > {
>
>
