On Mon, Mar 28, 2022 at 11:56:06PM +0000, Sean Christopherson wrote:
> On Thu, Mar 10, 2022, Chao Peng wrote:
> > @@ -2217,4 +2220,34 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
> > /* Max number of entries allowed for each kvm dirty ring */
> > #define KVM_DIRTY_RING_MAX_ENTRIES 65536
> >
> > +#ifdef CONFIG_MEMFILE_NOTIFIER
> > +static inline long kvm_memfile_get_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
> > + int *order)
> > +{
> > + pgoff_t index = gfn - slot->base_gfn +
> > + (slot->private_offset >> PAGE_SHIFT);
>
> This is broken for 32-bit kernels, where gfn_t is a 64-bit value but pgoff_t is a
> 32-bit value. There's no reason to support this for 32-bit kernels, so...
>
> The easiest fix, and likely most maintainable for other code too, would be to
> add a dedicated CONFIG for private memory, and then have KVM check that for all
> the memfile stuff. x86 can then select it only for 64-bit kernels, and in turn
> select MEMFILE_NOTIFIER iff private memory is supported.
>
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index ca7b2a6a452a..ee9c8c155300 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -48,7 +48,9 @@ config KVM
> select SRCU
> select INTERVAL_TREE
> select HAVE_KVM_PM_NOTIFIER if PM
> - select MEMFILE_NOTIFIER
> + select HAVE_KVM_PRIVATE_MEM if X86_64
> + select MEMFILE_NOTIFIER if HAVE_KVM_PRIVATE_MEM
> +
> help
> Support hosting fully virtualized guest machines using hardware
> virtualization extensions. You will need a fairly recent
>
> And in addition to replacing checks on CONFIG_MEMFILE_NOTIFIER, the probing of
> whether or not KVM_MEM_PRIVATE is allowed can be:
>
> @@ -1499,23 +1499,19 @@ static void kvm_replace_memslot(struct kvm *kvm,
> }
> }
>
> -bool __weak kvm_arch_private_memory_supported(struct kvm *kvm)
> -{
> - return false;
> -}
> -
> static int check_memory_region_flags(struct kvm *kvm,
> const struct kvm_userspace_memory_region *mem)
> {
> u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
>
> - if (kvm_arch_private_memory_supported(kvm))
> - valid_flags |= KVM_MEM_PRIVATE;
> -
> #ifdef __KVM_HAVE_READONLY_MEM
> valid_flags |= KVM_MEM_READONLY;
> #endif
>
> +#ifdef CONFIG_KVM_HAVE_PRIVATE_MEM
> + valid_flags |= KVM_MEM_PRIVATE;
> +#endif
One thing to mention is CONFIG_KVM_HAVE_PRIVATE_MEM is build-time thing.
Do you think we should or not do that for runtime? E.g. expose by vm_type
so only when TDX is enabled KVM_MEM_PRIVATE is exposed.
Chao
