[PATCH Part2 v6 30/49] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX and SNP

Ashish Kalra
2022-06-20T23:10:57Z

From: Sean Christopherson <sean.j.christopherson@intel.com>

Introduce a helper to directly (pun intended) fault-in a TDP page
without having to go through the full page fault path. This allows
TDX to get the resulting pfn and also allows the RET_PF_* enums to
stay in mmu.c where they belong.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kvm/mmu.h | 3 +++
arch/x86/kvm/mmu/mmu.c | 51 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e6cae6f22683..c99b15e97a0a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -204,6 +204,9 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
return vcpu->arch.mmu->page_fault(vcpu, &fault);
}

+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+ u32 error_code, int max_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 997318ecebd1..569021af349a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4100,6 +4100,57 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
return direct_page_fault(vcpu, fault);
}

+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+ u32 err, int max_level)
+{
+ struct kvm_page_fault fault = {
+ .addr = gpa,
+ .error_code = err,
+ .exec = err & PFERR_FETCH_MASK,
+ .write = err & PFERR_WRITE_MASK,
+ .present = err & PFERR_PRESENT_MASK,
+ .rsvd = err & PFERR_RSVD_MASK,
+ .user = err & PFERR_USER_MASK,
+ .prefetch = false,
+ .is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
+ .nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(),
+
+ .max_level = max_level,
+ .req_level = PG_LEVEL_4K,
+ .goal_level = PG_LEVEL_4K,
+ };
+ int r;
+
+ if (mmu_topup_memory_caches(vcpu, false))
+ return KVM_PFN_ERR_FAULT;
+
+ /*
+ * Loop on the page fault path to handle the case where an mmu_notifier
+ * invalidation triggers RET_PF_RETRY. In the normal page fault path,
+ * KVM needs to resume the guest in case the invalidation changed any
+ * of the page fault properties, i.e. the gpa or error code. For this
+ * path, the gpa and error code are fixed by the caller, and the caller
+ * expects failure if and only if the page fault can't be fixed.
+ */
+ do {
+ /*
+ * TODO: this should probably go through kvm_mmu_do_page_fault(),
+ * but we need a way to control the max_level, so maybe a direct
+ * call to kvm_tdp_page_fault, which will call into
+ * direct_page_fault() when appropriate.
+ */
+ //r = direct_page_fault(vcpu, &fault);
+#if CONFIG_RETPOLINE
+ if (fault.is_tdp)
+ r = kvm_tdp_page_fault(vcpu, &fault);
+#else
+ r = vcpu->arch.mmu->page_fault(vcpu, &fault);
+#endif
+ } while (r == RET_PF_RETRY && !is_error_noslot_pfn(fault.pfn));
+ return fault.pfn;
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_map_tdp_page);
+
static void nonpaging_init_context(struct kvm_mmu *context)
{
context->page_fault = nonpaging_page_fault;
--
2.25.1