On Thu, Dec 23, 2021, Chao Peng wrote:
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index 03b2ce34e7f4..86655cd660ca 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -46,6 +46,7 @@ config KVM
> select SRCU
> select INTERVAL_TREE
> select HAVE_KVM_PM_NOTIFIER if PM
> + select MEMFD_OPS
MEMFD_OPS is a weird Kconfig name given that it's not just memfd() that can
implement the ops.
> help
> Support hosting fully virtualized guest machines using hardware
> virtualization extensions. You will need a fairly recent
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 3bd875f9669f..21f8b1880723 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -806,6 +806,12 @@ static inline void kvm_irqfd_exit(void)
> {
> }
> #endif
> +
> +int kvm_memfd_register(struct kvm *kvm, struct kvm_memory_slot *slot);
> +void kvm_memfd_unregister(struct kvm_memory_slot *slot);
> +long kvm_memfd_get_pfn(struct kvm_memory_slot *slot, gfn_t gfn, int *order);
> +void kvm_memfd_put_pfn(kvm_pfn_t pfn);
> +
> int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> struct module *module);
> void kvm_exit(void);
> diff --git a/virt/kvm/Makefile.kvm b/virt/kvm/Makefile.kvm
> index ffdcad3cc97a..8842128d8429 100644
> --- a/virt/kvm/Makefile.kvm
> +++ b/virt/kvm/Makefile.kvm
> @@ -5,7 +5,7 @@
>
> KVM ?= ../../../virt/kvm
>
> -kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o
> +kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o $(KVM)/memfd.o
This should be
kvm-$(CONFIG_MEMFD_OPS) += $(KVM)/memfd.o
with stubs provided in a header file as needed. I also really dislike naming KVM's
file memfd.c, though I don't have a good alternative off the top of my head.
> kvm-$(CONFIG_KVM_VFIO) += $(KVM)/vfio.o
> kvm-$(CONFIG_KVM_MMIO) += $(KVM)/coalesced_mmio.o
> kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
> +#ifdef CONFIG_MEMFD_OPS
> +static const struct memfd_pfn_ops *memfd_ops;
memfd_ops needs to be associated with the slot, e.g. userspace should be able to
map multiple types of a backing stores into a single VM. This doesn't even allow
that for multiple VMs, and there are all kinds of ordering issues.
> +void kvm_memfd_unregister(struct kvm_memory_slot *slot)
> +{
> +#ifdef CONFIG_MEMFD_OPS
> + if (slot->file) {
> + fput(slot->file);
Needs to actually unregister.
> + slot->file = NULL;
> + }
> +#endif
> +}
> --
> 2.17.1
>
