Re: [RFC PATCH] kvm: x86/vmx: Use kzalloc for cached_vmcs12

[Paolo Bonzini]

On 15/01/19 03:43, Sean Christopherson wrote:
>> -	vmx->nested.cached_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL);
>> +	vmx->nested.cached_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL);
>>  	if (!vmx->nested.cached_vmcs12)
>>  		goto out_cached_vmcs12;
> Obviously not your code, but why do we allocate VMCS12_SIZE instead of
> sizeof(struct vmcs12)?  I get why we require userspace to reserve the
> full 4k, but I don't understand why KVM needs to allocate the reserved
> bytes internally.

It's just cleaner and shorter code to copy everything in and out,
instead of having to explicitly zero the slack.

Paolo