Re: [RFC PATCH 2/8] KVM: Add KVM_MAP_MEMORY vcpu ioctl to pre-populate guest memory

David Matlack
2024-03-07T00:49:24Z

On 2024-03-01 09:28 AM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index d1fd9cb5d037..d77c9b79d76b 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> +static int kvm_vcpu_map_memory(struct kvm_vcpu *vcpu,
> + struct kvm_memory_mapping *mapping)
> +{
> + bool added = false;
> + int idx, r = 0;
> +
> + if (mapping->flags & ~(KVM_MEMORY_MAPPING_FLAG_WRITE |
> + KVM_MEMORY_MAPPING_FLAG_EXEC |
> + KVM_MEMORY_MAPPING_FLAG_USER |
> + KVM_MEMORY_MAPPING_FLAG_PRIVATE))
> + return -EINVAL;
> + if ((mapping->flags & KVM_MEMORY_MAPPING_FLAG_PRIVATE) &&
> + !kvm_arch_has_private_mem(vcpu->kvm))
> + return -EINVAL;
> +
> + /* Sanity check */
> + if (!IS_ALIGNED(mapping->source, PAGE_SIZE) ||
> + !mapping->nr_pages ||
> + mapping->base_gfn + mapping->nr_pages <= mapping->base_gfn)
> + return -EINVAL;
> +
> + vcpu_load(vcpu);
> + idx = srcu_read_lock(&vcpu->kvm->srcu);
> + r = kvm_arch_vcpu_pre_map_memory(vcpu);
> + if (r)
> + return r;
> +
> + while (mapping->nr_pages) {
> + if (signal_pending(current)) {
> + r = -ERESTARTSYS;
> + break;
> + }
> +
> + if (need_resched())

nit: Is need_resched() superfluous when calling cond_resched()?

> + cond_resched();
> +
> + r = kvm_arch_vcpu_map_memory(vcpu, mapping);
> + if (r)
> + break;
> +
> + added = true;
> + }
> +
> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
> + vcpu_put(vcpu);
> +
> + if (added && mapping->nr_pages > 0)
> + r = -EAGAIN;

This can overwrite the return value from kvm_arch_vcpu_map_memory().