KVM: Add KVM_PRE_FAULT_MEMORY vcpu ioctl to pre-populate guest memory

Add a new ioctl KVM_PRE_FAULT_MEMORY in the KVM common code. It iterates on the
memory range and calls the arch-specific function.  The implementation is
optional and enabled by a Kconfig symbol.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <819322b8f25971f2b9933bfa4506e618508ad782.1712785629.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7b57878c8c184dd6fc2bcca38745f0dab44f2aff..c3c922bf077f7647b43d4278129fd6fea7cb485e 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2477,4 +2477,9 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long npages
 void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
 #endif
 
+#ifdef CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY
+long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
+                                   struct kvm_pre_fault_memory *range);
+#endif
+
 #endif

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d03842abae5784cf4e4d0d361d14e3c04acc5467..e5af8c692dc063de39a083db4c8694376de4f3f1 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -917,6 +917,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_MEMORY_ATTRIBUTES 233
 #define KVM_CAP_GUEST_MEMFD 234
 #define KVM_CAP_VM_TYPES 235
+#define KVM_CAP_PRE_FAULT_MEMORY 236
 
 struct kvm_irq_routing_irqchip {
        __u32 irqchip;
@@ -1548,4 +1549,13 @@ struct kvm_create_guest_memfd {
        __u64 reserved[6];
 };
 
+#define KVM_PRE_FAULT_MEMORY   _IOWR(KVMIO, 0xd5, struct kvm_pre_fault_memory)
+
+struct kvm_pre_fault_memory {
+       __u64 gpa;
+       __u64 size;
+       __u64 flags;
+       __u64 padding[5];
+};
+
 #endif /* __LINUX_KVM_H */

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 754c6c923427f9eeb4358130f64b318630f69782..b14e14cdbfb9fd800b45c9d76d3a7a5ea3a44be4 100644 (file)
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -67,6 +67,9 @@ config HAVE_KVM_INVALID_WAKEUPS
 config KVM_GENERIC_DIRTYLOG_READ_PROTECT
        bool
 
+config KVM_GENERIC_PRE_FAULT_MEMORY
+       bool
+
 config KVM_COMPAT
        def_bool y
        depends on KVM && COMPAT && !(S390 || ARM64 || RISCV)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8e422c2c9450fd6f36dc0ea85bacc22e587c2dd9..f817ec66c85ffcb7d7ea83384333bbd7abc65cfd 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4373,6 +4373,52 @@ static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
        return fd;
 }
 
+#ifdef CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY
+static int kvm_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
+                                    struct kvm_pre_fault_memory *range)
+{
+       int idx;
+       long r;
+       u64 full_size;
+
+       if (range->flags)
+               return -EINVAL;
+
+       if (!PAGE_ALIGNED(range->gpa) ||
+           !PAGE_ALIGNED(range->size) ||
+           range->gpa + range->size <= range->gpa)
+               return -EINVAL;
+
+       vcpu_load(vcpu);
+       idx = srcu_read_lock(&vcpu->kvm->srcu);
+
+       full_size = range->size;
+       do {
+               if (signal_pending(current)) {
+                       r = -EINTR;
+                       break;
+               }
+
+               r = kvm_arch_vcpu_pre_fault_memory(vcpu, range);
+               if (WARN_ON_ONCE(r == 0 || r == -EIO))
+                       break;
+
+               if (r < 0)
+                       break;
+
+               range->size -= r;
+               range->gpa += r;
+               cond_resched();
+       } while (range->size);
+
+       srcu_read_unlock(&vcpu->kvm->srcu, idx);
+       vcpu_put(vcpu);
+
+       /* Return success if at least one page was mapped successfully.  */
+       return full_size == range->size ? r : 0;
+}
+#endif
+
 static long kvm_vcpu_ioctl(struct file *filp,
                           unsigned int ioctl, unsigned long arg)
 {
@@ -4573,6 +4619,20 @@ out_free1:
                r = kvm_vcpu_ioctl_get_stats_fd(vcpu);
                break;
        }
+#ifdef CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY
+       case KVM_PRE_FAULT_MEMORY: {
+               struct kvm_pre_fault_memory range;
+
+               r = -EFAULT;
+               if (copy_from_user(&range, argp, sizeof(range)))
+                       break;
+               r = kvm_vcpu_pre_fault_memory(vcpu, &range);
+               /* Pass back leftover range. */
+               if (copy_to_user(argp, &range, sizeof(range)))
+                       r = -EFAULT;
+               break;
+       }
+#endif
        default:
                r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
        }