Re: [PATCH v3 20/21] KVM: arm64: Remove unused 'pgd' field from 'struct kvm_s2_mmu'

Gavin Shan
2020-09-03T05:08:42Z

Hi Will,

On 8/25/20 7:39 PM, Will Deacon wrote:
> The stage-2 page-tables are entirely encapsulated by the 'pgt' field of
> 'struct kvm_s2_mmu', so remove the unused 'pgd' field.
>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Quentin Perret <qperret@google.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
> arch/arm64/include/asm/kvm_host.h | 1 -
> arch/arm64/kvm/mmu.c | 2 --
> 2 files changed, 3 deletions(-)
>

I think this might be folded into PATCH[18] as both patches are
simple enough. I'm not sure the changes introduced in PATCH[19]
prevent us doing this.

There is another question below.

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 0b7c702b2151..41caf29bd93c 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -79,7 +79,6 @@ struct kvm_s2_mmu {
> * for vEL1/EL0 with vHCR_EL2.VM == 0. In that case, we use the
> * canonical stage-2 page tables.
> */
> - pgd_t *pgd;
> phys_addr_t pgd_phys;
> struct kvm_pgtable *pgt;
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index ddeec0b03666..f28e03dcb897 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -384,7 +384,6 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu)
> mmu->kvm = kvm;
> mmu->pgt = pgt;
> mmu->pgd_phys = __pa(pgt->pgd);
> - mmu->pgd = (void *)pgt->pgd;
> mmu->vmid.vmid_gen = 0;
> return 0;
>
> @@ -470,7 +469,6 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
> spin_lock(&kvm->mmu_lock);
> pgt = mmu->pgt;
> if (pgt) {
> - mmu->pgd = NULL;
> mmu->pgd_phys = 0;
> mmu->pgt = NULL;
> free_percpu(mmu->last_vcpu_ran);
>

I guess mmu->pgd_phys might be removed either because kvm_get_vttbr()
is the only consumer.

Thanks,
Gavin