On Wed, Feb 15, 2023 at 01:16:13AM +0000, Anish Moorthy wrote:
> Just do atomic gfn_to_pfn_memslot when the cap is enabled. Since we
> don't have to deal with async page faults, the implementation is even
> simpler than on x86
All of Sean's suggestions about writing a change description apply here
too.
> Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx>
> Acked-by: James Houghton <jthoughton@xxxxxxxxxx>
> ---
> arch/arm64/kvm/arm.c | 1 +
> arch/arm64/kvm/mmu.c | 14 ++++++++++++--
> 2 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 698787ed87e92..31bec7866c346 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -220,6 +220,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_VCPU_ATTRIBUTES:
> case KVM_CAP_PTP_KVM:
> case KVM_CAP_ARM_SYSTEM_SUSPEND:
> + case KVM_CAP_MEM_FAULT_NOWAIT:
> r = 1;
> break;
> case KVM_CAP_SET_GUEST_DEBUG2:
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 01352f5838a00..964af7cd5f1c8 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1206,6 +1206,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> unsigned long vma_pagesize, fault_granule;
> enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
> struct kvm_pgtable *pgt;
> + bool mem_fault_nowait;
>
> fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);
> write_fault = kvm_is_write_fault(vcpu);
> @@ -1301,8 +1302,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> */
> smp_rmb();
>
> - pfn = __gfn_to_pfn_memslot(memslot, gfn, false, false, NULL,
> - write_fault, &writable, NULL);
> + mem_fault_nowait = memory_faults_enabled(vcpu->kvm);
> + pfn = __gfn_to_pfn_memslot(
> + memslot, gfn, mem_fault_nowait, false, NULL,
> + write_fault, &writable, NULL);
> +
> + if (mem_fault_nowait && pfn == KVM_PFN_ERR_FAULT) {
> + vcpu->run->exit_reason = KVM_EXIT_MEMORY_FAULT;
> + vcpu->run->memory_fault.gpa = gfn << PAGE_SHIFT;
> + vcpu->run->memory_fault.size = vma_pagesize;
> + return -EFAULT;
We really don't want to get out to userspace with EFAULT. Instead, we
should get out to userspace with 0 as the return code to indicate a
'normal' / expected exit.
That will require a bit of redefinition on user_mem_abort()'s return
values:
- < 0, return to userspace with an error
- 0, return to userspace for a 'normal' exit
- 1, resume the guest
--
Thanks,
Oliver
