Hi Jing,
On Tue, Jan 18, 2022 at 1:57 AM Jing Zhang <jingzhangos@xxxxxxxxxx> wrote:
>
> To reduce MMU lock contention during dirty logging, all permission
> relaxation operations would be performed under read lock.
>
> Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
> ---
> arch/arm64/kvm/mmu.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index cafd5813c949..10df5d855d54 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1080,6 +1080,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> gfn_t gfn;
> kvm_pfn_t pfn;
> bool logging_active = memslot_is_logging(memslot);
> + bool logging_perm_fault = false;
> unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu);
> unsigned long vma_pagesize, fault_granule;
> enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
> @@ -1114,6 +1115,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (logging_active) {
> force_pte = true;
> vma_shift = PAGE_SHIFT;
> + logging_perm_fault = (fault_status == FSC_PERM && write_fault);
> } else {
> vma_shift = get_vma_page_shift(vma, hva);
> }
> @@ -1212,7 +1214,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (exec_fault && device)
> return -ENOEXEC;
>
> - write_lock(&kvm->mmu_lock);
> + /*
> + * To reduce MMU contentions and enhance concurrency during dirty
> + * logging dirty logging, only acquire read lock for permission
> + * relaxation.
> + */
A couple of nits:
"dirty logging" is repeated twice
s/contentions/contention
Other than that,
Tested-by: Fuad Tabba <tabba@xxxxxxxxxx>
Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>
Thanks,
/fuad
> + if (logging_perm_fault)
> + read_lock(&kvm->mmu_lock);
> + else
> + write_lock(&kvm->mmu_lock);
> pgt = vcpu->arch.hw_mmu->pgt;
> if (mmu_notifier_retry(kvm, mmu_seq))
> goto out_unlock;
> @@ -1271,7 +1281,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> }
>
> out_unlock:
> - write_unlock(&kvm->mmu_lock);
> + if (logging_perm_fault)
> + read_unlock(&kvm->mmu_lock);
> + else
> + write_unlock(&kvm->mmu_lock);
> kvm_set_pfn_accessed(pfn);
> kvm_release_pfn_clean(pfn);
> return ret != -EAGAIN ? ret : 0;
> --
> 2.34.1.703.g22d0c6ccf7-goog
>
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