When checking for overlapping slots on registration of a new one, kvm currently also considers zero-length (ie. deleted) slots and rejects requests incorrectly. This finally denies user space from joining slots. Fix the check by skipping deleted slots and advertise this via a KVM_CAP_JOIN_MEMORY_REGIONS_WORKS.
Signed-off-by: Jan Kiszka <[email protected]> --- include/linux/kvm.h | 2 ++ virt/kvm/kvm_main.c | 3 ++- 2 files changed, 4 insertions(+), 1 deletions(-) diff --git a/include/linux/kvm.h b/include/linux/kvm.h index ee755e2..644e3a9 100644 --- a/include/linux/kvm.h +++ b/include/linux/kvm.h @@ -413,6 +413,8 @@ struct kvm_trace_rec { #define KVM_CAP_DEVICE_MSIX 28 #endif #define KVM_CAP_ASSIGN_DEV_IRQ 29 +/* Another bug in KVM_SET_USER_MEMORY_REGION fixed: */ +#define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30 #ifdef KVM_CAP_IRQ_ROUTING diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 363af32..3265566 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1117,7 +1117,7 @@ int __kvm_set_memory_region(struct kvm *kvm, for (i = 0; i < KVM_MEMORY_SLOTS; ++i) { struct kvm_memory_slot *s = &kvm->memslots[i]; - if (s == memslot) + if (s == memslot || !s->npages) continue; if (!((base_gfn + npages <= s->base_gfn) || (base_gfn >= s->base_gfn + s->npages))) @@ -2262,6 +2262,7 @@ static long kvm_dev_ioctl_check_extension_generic(long arg) switch (arg) { case KVM_CAP_USER_MEMORY: case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: + case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS: return 1; #ifdef CONFIG_HAVE_KVM_IRQCHIP case KVM_CAP_IRQ_ROUTING:
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