KVM: x86/mmu: Decrease indentation in logic to sync new indirect shadow page

Combine the back-to-back if-statements for synchronizing children when
linking a new indirect shadow page in order to decrease the indentation,
and to make it easier to "see" the logic in its entirety.

No functional change intended.

Link: https://lore.kernel.org/r/20240802203900.348808-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 69941cebb3a87eae90b63b7cd49975d00b11315e..0e97e080a997e9bbffbdb67ce7e79b7ea4f68654 100644 (file)
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -674,27 +674,25 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
                sp = kvm_mmu_get_child_sp(vcpu, it.sptep, table_gfn,
                                          false, access);
 
-               if (sp != ERR_PTR(-EEXIST)) {
-                       /*
-                        * We must synchronize the pagetable before linking it
-                        * because the guest doesn't need to flush tlb when
-                        * the gpte is changed from non-present to present.
-                        * Otherwise, the guest may use the wrong mapping.
-                        *
-                        * For PG_LEVEL_4K, kvm_mmu_get_page() has already
-                        * synchronized it transiently via kvm_sync_page().
-                        *
-                        * For higher level pagetable, we synchronize it via
-                        * the slower mmu_sync_children().  If it needs to
-                        * break, some progress has been made; return
-                        * RET_PF_RETRY and retry on the next #PF.
-                        * KVM_REQ_MMU_SYNC is not necessary but it
-                        * expedites the process.
-                        */
-                       if (sp->unsync_children &&
-                           mmu_sync_children(vcpu, sp, false))
-                               return RET_PF_RETRY;
-               }
+               /*
+                * Synchronize the new page before linking it, as the CPU (KVM)
+                * is architecturally disallowed from inserting non-present
+                * entries into the TLB, i.e. the guest isn't required to flush
+                * the TLB when changing the gPTE from non-present to present.
+                *
+                * For PG_LEVEL_4K, kvm_mmu_find_shadow_page() has already
+                * synchronized the page via kvm_sync_page().
+                *
+                * For higher level pages, which cannot be unsync themselves
+                * but can have unsync children, synchronize via the slower
+                * mmu_sync_children().  If KVM needs to drop mmu_lock due to
+                * contention or to reschedule, instruct the caller to retry
+                * the #PF (mmu_sync_children() ensures forward progress will
+                * be made).
+                */
+               if (sp != ERR_PTR(-EEXIST) && sp->unsync_children &&
+                   mmu_sync_children(vcpu, sp, false))
+                       return RET_PF_RETRY;
 
                /*
                 * Verify that the gpte in the page we've just write