On 27.01.2021 18:57, Vitaly Kuznetsov wrote:
Limiting the maximum number of user memslots globally can be undesirable as different VMs may have different needs. Generally, a relatively small number should suffice and a VMM may want to enforce the limitation so a VM won't accidentally eat too much memory. On the other hand, the number of required memslots can depend on the number of assigned vCPUs, e.g. each Hyper-V SynIC may require up to two additional slots per vCPU. Prepare to limit the maximum number of user memslots per-VM. No real functional change in this patch as the limit is still hard-coded to KVM_USER_MEM_SLOTS. Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> ---
Perhaps I didn't understand the idea clearly but I thought it was to protect the kernel from a rogue userspace VMM allocating many memslots and so consuming a lot of memory in kernel? But then what's the difference between allocating 32k memslots for one VM and allocating 509 slots for 64 VMs? A guest can't add a memslot on its own, only the host software (like QEMU) can, right? Thanks, Maciej
