Re: [PATCH 05/10] KVM/nVMX: Use kvm_vcpu_map when mapping the L1 MSR bitmap

Paolo Bonzini
2018-04-12T14:36:27Z

On 21/02/2018 18:47, KarimAllah Ahmed wrote:
> ... since using kvm_vcpu_gpa_to_page() and kmap() will only work for guest
> memory that has a "struct page".
>
> The life-cycle of the mapping also changes to avoid doing map and unmap on
> every single exit (which becomes very expesive once we use memremap). Now
> the memory is mapped and only unmapped when a new VMCS12 is loaded into the
> vCPU (or when the vCPU is freed!).

In this particular case SMM is not an issue because it cannot use VMX.
Therefore it's safe to ignore non-SMM address spaces. You can then
introduce

int kvm_map_gfn(struct kvm_vcpu *vcpu gfn_t gfn,
struct kvm_host_map *map)

calling kvm_gfn_to_memslot + __kvm_map_gfn

which could also handle the caching aspect. But please let's look at it
later, making the lifecycle change separate from the new API.

Paolo

> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
> ---
> arch/x86/kvm/vmx.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)