Re: [RFC PATCH 01/37] KVM: x86/mmu: Store the address space ID directly in kvm_mmu_page_role

Yang, Weijiang
2022-12-09T02:38:56Z

On 12/9/2022 3:38 AM, David Matlack wrote:
> Rename kvm_mmu_page_role.smm with kvm_mmu_page_role.as_id and use it
> directly as the address space ID throughout the KVM MMU code. This
> eliminates a needless level of indirection, kvm_mmu_role_as_id(), and
> prepares for making kvm_mmu_page_role architecture-neutral.
>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
> arch/x86/include/asm/kvm_host.h | 4 ++--
> arch/x86/kvm/mmu/mmu.c | 6 +++---
> arch/x86/kvm/mmu/mmu_internal.h | 10 ----------
> arch/x86/kvm/mmu/tdp_iter.c | 2 +-
> arch/x86/kvm/mmu/tdp_mmu.c | 12 ++++++------
> 5 files changed, 12 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index aa4eb8cfcd7e..0a819d40131a 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -348,7 +348,7 @@ union kvm_mmu_page_role {
> * simple shift. While there is room, give it a whole
> * byte so it is also faster to load it from memory.
> */
> - unsigned smm:8;
> + unsigned as_id:8;
> };
> };
>
> @@ -2056,7 +2056,7 @@ enum {
> # define __KVM_VCPU_MULTIPLE_ADDRESS_SPACE
> # define KVM_ADDRESS_SPACE_NUM 2
> # define kvm_arch_vcpu_memslots_id(vcpu) ((vcpu)->arch.hflags & HF_SMM_MASK ? 1 : 0)
> -# define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, (role).smm)
> +# define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, (role).as_id)
> #else
> # define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, 0)
> #endif
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 4d188f056933..f375b719f565 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5056,7 +5056,7 @@ kvm_calc_cpu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
> union kvm_cpu_role role = {0};
>
> role.base.access = ACC_ALL;
> - role.base.smm = is_smm(vcpu);
> + role.base.as_id = is_smm(vcpu);

I'm not familiar with other architectures, is there similar conception
as x86 smm mode?

If not, maybe need to re-shape is_smm() as a common helper to get the as_id. …