On Wed, Jan 04, 2023 at 12:03:44PM +0000, Jarkko Sakkinen wrote:
> On Wed, Dec 14, 2022 at 01:39:54PM -0600, Michael Roth wrote:
> > This mainly indicates to KVM that it should expect all private guest
> > memory to be backed by private memslots. Ideally this would work
> > similarly for others archs, give or take a few additional flags, but
> > for now it's a simple boolean indicator for x86.
> >
> > Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> > ---
> > arch/x86/include/asm/kvm_host.h | 3 +++
> > arch/x86/kvm/x86.c | 10 ++++++++++
> > include/uapi/linux/kvm.h | 1 +
> > 3 files changed, 14 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 27ef31133352..2b6244525107 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1438,6 +1438,9 @@ struct kvm_arch {
> > */
> > #define SPLIT_DESC_CACHE_MIN_NR_OBJECTS (SPTE_ENT_PER_PAGE + 1)
> > struct kvm_mmu_memory_cache split_desc_cache;
> > +
> > + /* Use/enforce unmapped private memory. */
> > + bool upm_mode;
> > };
> >
> > struct kvm_vm_stat {
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index c67e22f3e2ee..99ecf99bc4d2 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -4421,6 +4421,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> > case KVM_CAP_EXIT_HYPERCALL:
> > r = KVM_EXIT_HYPERCALL_VALID_MASK;
> > break;
> > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
> > + case KVM_CAP_UNMAPPED_PRIVATE_MEM:
> > + r = 1;
> > + break;
> > +#endif
> > case KVM_CAP_SET_GUEST_DEBUG2:
> > return KVM_GUESTDBG_VALID_MASK;
> > #ifdef CONFIG_KVM_XEN
> > @@ -6382,6 +6387,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
> > }
> > mutex_unlock(&kvm->lock);
> > break;
> > + case KVM_CAP_UNMAPPED_PRIVATE_MEM:
> > + kvm->arch.upm_mode = true;
> > + r = 0;
> > + break;
> > default:
> > r = -EINVAL;
> > break;
> > @@ -12128,6 +12137,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> > kvm->arch.default_tsc_khz = max_tsc_khz ? : tsc_khz;
> > kvm->arch.guest_can_read_msr_platform_info = true;
> > kvm->arch.enable_pmu = enable_pmu;
> > + kvm->arch.upm_mode = false;
> >
> > #if IS_ENABLED(CONFIG_HYPERV)
> > spin_lock_init(&kvm->arch.hv_root_tdp_lock);
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index c7e9d375a902..cc9424ccf9b2 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -1219,6 +1219,7 @@ struct kvm_ppc_resize_hpt {
> > #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223
> > #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224
> > #define KVM_CAP_MEMORY_ATTRIBUTES 225
> > +#define KVM_CAP_UNMAPPED_PRIVATE_MEM 240
> >
> > #ifdef KVM_CAP_IRQ_ROUTING
> >
> > --
> > 2.25.1
> >
>
> Why we want to carry non-UPM support still?
For SNP, non-UPM support is no longer included in this patchset.
However, this patchset also adds support for UPM-based SEV (for lazy-pinning
support). So we still need a way to let userspace switch between those 2
modes.
-Mike
>
> BR, Jarkko
>
