On Wed, Apr 17, 2024, Paolo Bonzini wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Introduce a helper function to call the KVM fault handler. It allows a new
> ioctl to invoke the KVM fault handler to populate without seeing RET_PF_*
> enums or other KVM MMU internal definitions because RET_PF_* are internal
> to x86 KVM MMU. The implementation is restricted to two-dimensional paging
> for simplicity. The shadow paging uses GVA for faulting instead of L1 GPA.
> It makes the API difficult to use.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Message-ID: <9b866a0ae7147f96571c439e75429a03dcb659b6.1712785629.git.isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.h | 3 +++
> arch/x86/kvm/mmu/mmu.c | 32 ++++++++++++++++++++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index e8b620a85627..51ff4f67e115 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -183,6 +183,9 @@ static inline void kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
> __kvm_mmu_refresh_passthrough_bits(vcpu, mmu);
> }
>
> +int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
> + u8 *level);
> +
> /*
> * Check if a given access (described through the I/D, W/R and U/S bits of a
> * page fault error code pfec) causes a permission fault with the given PTE
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 7fbcfc97edcc..fb2149d16f8d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4646,6 +4646,38 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> return direct_page_fault(vcpu, fault);
> }
>
> +int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
> + u8 *level)
If the return is an overloaded "long", then there's no need for @level, i.e. do
the level=>size conversion in this helper.
> +{
> + int r;
> +
> + /* Restrict to TDP page fault. */
Do we want to restrict this to the TDP MMU? Not for any particular reason, mostly
just to keep moving towards officially deprecating/removing TDP support from the
shadow MMU.
> + if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault)
> + return -EOPNOTSUPP;
> +
> + r = __kvm_mmu_do_page_fault(vcpu, gpa, error_code, true, NULL, level);
> + if (r < 0)
> + return r;
> +
> + switch (r) {
> + case RET_PF_RETRY:
> + return -EAGAIN;
> +
> + case RET_PF_FIXED:
> + case RET_PF_SPURIOUS:
> + return 0;
Going with the "long" idea, this becomes:
end = (gpa & KVM_HPAGE_MASK(level)) + KVM_HPAGE_SIZE(level);
return min(size, end - gpa);
though I would vote for a:
break;
so that the happy path is nicely isolated at the end of the function.
> +
> + case RET_PF_EMULATE:
> + return -EINVAL;
> +
> + case RET_PF_CONTINUE:
> + case RET_PF_INVALID:
> + default:
> + WARN_ON_ONCE(r);
> + return -EIO;
> + }
> +}
> +
> static void nonpaging_init_context(struct kvm_mmu *context)
> {
> context->page_fault = nonpaging_page_fault;
> --
> 2.43.0
>
>
