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

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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>
This commit is contained in:
Isaku Yamahata 2024-04-10 15:07:28 -07:00 committed by Paolo Bonzini
parent 9aed7a6c0b
commit bc1a5cd002
4 changed files with 78 additions and 0 deletions
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5
include/linux/kvm_host.h
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@ -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); void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
#endif #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 #endif

10
include/uapi/linux/kvm.h
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@ -917,6 +917,7 @@ struct kvm_enable_cap {
#define KVM_CAP_MEMORY_ATTRIBUTES 233 #define KVM_CAP_MEMORY_ATTRIBUTES 233
#define KVM_CAP_GUEST_MEMFD 234 #define KVM_CAP_GUEST_MEMFD 234
#define KVM_CAP_VM_TYPES 235 #define KVM_CAP_VM_TYPES 235
#define KVM_CAP_PRE_FAULT_MEMORY 236
struct kvm_irq_routing_irqchip { struct kvm_irq_routing_irqchip {
__u32 irqchip; __u32 irqchip;
@ -1548,4 +1549,13 @@ struct kvm_create_guest_memfd {
__u64 reserved[6]; __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 */ #endif /* __LINUX_KVM_H */

3
virt/kvm/Kconfig
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@ -67,6 +67,9 @@ config HAVE_KVM_INVALID_WAKEUPS
config KVM_GENERIC_DIRTYLOG_READ_PROTECT config KVM_GENERIC_DIRTYLOG_READ_PROTECT
bool bool
config KVM_GENERIC_PRE_FAULT_MEMORY
bool
config KVM_COMPAT config KVM_COMPAT
def_bool y def_bool y
depends on KVM && COMPAT && !(S390 || ARM64 || RISCV) depends on KVM && COMPAT && !(S390 || ARM64 || RISCV)

60
virt/kvm/kvm_main.c
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@ -4373,6 +4373,52 @@ static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
return fd; 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, static long kvm_vcpu_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg) unsigned int ioctl, unsigned long arg)
{ {
@ -4573,6 +4619,20 @@ out_free1:
r = kvm_vcpu_ioctl_get_stats_fd(vcpu); r = kvm_vcpu_ioctl_get_stats_fd(vcpu);
break; 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: default:
r = kvm_arch_vcpu_ioctl(filp, ioctl, arg); r = kvm_arch_vcpu_ioctl(filp, ioctl, arg);
} }