Re: [PATCH v2 02/29] LoongArch: KVM: Implement kvm module related interface

[Tianrui Zhao]

在 2023年02月21日 01:46, Paolo Bonzini 写道:
> On 2/20/23 07:57, Tianrui Zhao wrote:
> > +    order = get_order(kvm_vector_size + kvm_enter_guest_size);
> > +    addr = (void *)__get_free_pages(GFP_KERNEL, order);
> > +    if (!addr) {
> > +        free_percpu(vmcs);
> > +        return -ENOMEM;
> > +    }
> > +
> > +    memcpy(addr, kvm_vector_entry, kvm_vector_size);
> > +    memcpy(addr + kvm_vector_size, kvm_enter_guest, 
> > kvm_enter_guest_size);
> > +    flush_icache_range((unsigned long)addr, (unsigned long)addr +
> > +                kvm_vector_size + kvm_enter_guest_size);
> > +
> > +    vpid_mask = read_csr_gstat();
> > +    vpid_mask = (vpid_mask & CSR_GSTAT_GIDBIT) >> 
> > CSR_GSTAT_GIDBIT_SHIFT;
> > +    if (vpid_mask)
> > +        vpid_mask = GENMASK(vpid_mask - 1, 0);
> > +
> > +    for_each_possible_cpu(cpu) {
> > +        context = per_cpu_ptr(vmcs, cpu);
> > +        context->vpid_mask = vpid_mask;
> > +        context->vpid_cache = context->vpid_mask + 1;
> > +        context->last_vcpu = NULL;
> > +        context->kvm_eentry = addr;
> > +        context->kvm_enter_guest = addr + kvm_vector_size;
> > +        context->page_order = order;
> > +    }
>
> A lot of these variables are constant across all pCPUs, any reason to 
> have them in a per-CPU variable?  Likewise, since they are all the 
> same as the constant global vmcs variable, why make them part of 
> struct kvm_context instead of just making them globals?

Ok thanks, it is more appropriate to use global variables to save those 
information.

Thanks
Tianrui Zhao

> Also, why does the world switch code need a copy?
>
> Paolo