diff --git a/libraries/libmesosphere/include/mesosphere/board/nintendo/nx/kern_k_memory_layout.board.nintendo_nx.hpp b/libraries/libmesosphere/include/mesosphere/board/nintendo/nx/kern_k_memory_layout.board.nintendo_nx.hpp
new file mode 100644
index 000000000..beb1775f9
--- /dev/null
+++ b/libraries/libmesosphere/include/mesosphere/board/nintendo/nx/kern_k_memory_layout.board.nintendo_nx.hpp
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+#include <mesosphere/kern_common.hpp>
+
+namespace ams::kern {
+
+    constexpr inline size_t MainMemorySize = 4_GB;
+
+}
diff --git a/libraries/libmesosphere/include/mesosphere/kern_k_memory_layout.hpp b/libraries/libmesosphere/include/mesosphere/kern_k_memory_layout.hpp
index 690679a3b..d70485b62 100644
--- a/libraries/libmesosphere/include/mesosphere/kern_k_memory_layout.hpp
+++ b/libraries/libmesosphere/include/mesosphere/kern_k_memory_layout.hpp
@@ -17,6 +17,12 @@
 #include <mesosphere/kern_common.hpp>
 #include <mesosphere/init/kern_init_page_table_select.hpp>
 
+#if defined(ATMOSPHERE_BOARD_NINTENDO_NX)
+    #include <mesosphere/board/nintendo/nx/kern_k_memory_layout.board.nintendo_nx.hpp>
+#else
+    #error "Unknown board for KMemoryLayout"
+#endif
+
 namespace ams::kern {
 
     constexpr size_t KernelAslrAlignment = 2_MB;
diff --git a/libraries/libmesosphere/source/kern_k_page_table_base.cpp b/libraries/libmesosphere/source/kern_k_page_table_base.cpp
index 82235b7fe..13fb231d8 100644
--- a/libraries/libmesosphere/source/kern_k_page_table_base.cpp
+++ b/libraries/libmesosphere/source/kern_k_page_table_base.cpp
@@ -1077,7 +1077,119 @@ namespace ams::kern {
     }
 
     Result KPageTableBase::SetHeapSize(KProcessAddress *out, size_t size) {
-        MESOSPHERE_UNIMPLEMENTED();
+        /* Lock the physical memory mutex. */
+        KScopedLightLock map_phys_mem_lk(this->map_physical_memory_lock);
+
+        /* Try to perform a reduction in heap, instead of an extension. */
+        KProcessAddress cur_address;
+        size_t allocation_size;
+        {
+            /* Lock the table. */
+            KScopedLightLock lk(this->general_lock);
+
+            /* Validate that setting heap size is possible at all. */
+            R_UNLESS(!this->is_kernel,                                                             svc::ResultOutOfMemory());
+            R_UNLESS(size <= static_cast<size_t>(this->heap_region_end - this->heap_region_start), svc::ResultOutOfMemory());
+            R_UNLESS(size <= this->max_heap_size,                                                  svc::ResultOutOfMemory());
+
+            if (size < static_cast<size_t>(this->current_heap_end - this->heap_region_start)) {
+                /* The size being requested is less than the current size, so we need to free the end of the heap. */
+
+                /* Create an update allocator. */
+                KMemoryBlockManagerUpdateAllocator allocator(this->memory_block_slab_manager);
+                R_TRY(allocator.GetResult());
+
+                /* We're going to perform an update, so create a helper. */
+                KScopedPageTableUpdater updater(this);
+
+                /* Validate memory state. */
+                R_TRY(this->CheckMemoryState(this->heap_region_start + size, (this->heap_region_end - this->heap_region_start) - size,
+                                             KMemoryState_All, KMemoryState_Normal,
+                                             KMemoryPermission_All, KMemoryPermission_UserReadWrite,
+                                             KMemoryAttribute_All,  KMemoryAttribute_None));
+
+                /* Unmap the end of the heap. */
+                const size_t num_pages = ((this->current_heap_end - this->heap_region_start) - size) / PageSize;
+                const KPageProperties unmap_properties = { KMemoryPermission_None, false, false, false };
+                R_TRY(this->Operate(updater.GetPageList(), this->heap_region_start + size, num_pages, Null<KPhysicalAddress>, false, unmap_properties, OperationType_Unmap, false));
+
+                /* Release the memory from the resource limit. */
+                GetCurrentProcess().ReleaseResource(ams::svc::LimitableResource_PhysicalMemoryMax, num_pages * PageSize);
+
+                /* Apply the memory block update. */
+                this->memory_block_manager.Update(std::addressof(allocator), this->heap_region_start + size, num_pages, KMemoryState_Free, KMemoryPermission_None, KMemoryAttribute_None);
+
+                /* Update the current heap end. */
+                this->current_heap_end = this->heap_region_start + size;
+
+                /* Set the output. */
+                *out = this->heap_region_start;
+                return ResultSuccess();
+            } else if (size == static_cast<size_t>(this->current_heap_end - this->heap_region_start)) {
+                /* The size requested is exactly the current size. */
+                *out = this->heap_region_start;
+                return ResultSuccess();
+            } else {
+                /* We have to allocate memory. Determine how much to allocate and where while the table is locked. */
+                cur_address     = this->current_heap_end;
+                allocation_size = size - (this->current_heap_end - this->heap_region_start);
+            }
+        }
+
+        /* Reserve memory for the heap extension. */
+        KScopedResourceReservation memory_reservation(GetCurrentProcess().GetResourceLimit(), ams::svc::LimitableResource_PhysicalMemoryMax, allocation_size);
+        R_UNLESS(memory_reservation.Succeeded(), svc::ResultLimitReached());
+
+        /* Allocate pages for the heap extension. */
+        KPageGroup pg(this->block_info_manager);
+        R_TRY(Kernel::GetMemoryManager().Allocate(std::addressof(pg), allocation_size / PageSize, this->allocate_option));
+
+        /* Open the pages in the group for the duration of the call, and close them at the end. */
+        /* If the mapping succeeds, each page will gain an extra reference, otherwise they will be freed automatically. */
+        pg.Open();
+        ON_SCOPE_EXIT { pg.Close(); };
+
+        /* Clear all the newly allocated pages. */
+        for (const auto &it : pg) {
+            std::memset(GetVoidPointer(it.GetAddress()), this->heap_fill_value, it.GetSize());
+        }
+
+        /* Map the pages. */
+        {
+            /* Lock the table. */
+            KScopedLightLock lk(this->general_lock);
+
+            /* Create an update allocator. */
+            KMemoryBlockManagerUpdateAllocator allocator(this->memory_block_slab_manager);
+            R_TRY(allocator.GetResult());
+
+            /* We're going to perform an update, so create a helper. */
+            KScopedPageTableUpdater updater(this);
+
+            /* Ensure that the heap hasn't changed since we began executing. */
+            MESOSPHERE_ABORT_UNLESS(cur_address == this->current_heap_end);
+
+            /* Check the memory state. */
+            R_TRY(this->CheckMemoryState(this->current_heap_end, allocation_size, KMemoryState_All, KMemoryState_Free, KMemoryPermission_None, KMemoryPermission_None, KMemoryAttribute_None, KMemoryAttribute_None));
+
+            /* Map the pages. */
+            const size_t num_pages = allocation_size / PageSize;
+            const KPageProperties map_properties = { KMemoryPermission_UserReadWrite, false, false, false };
+            R_TRY(this->Operate(updater.GetPageList(), this->current_heap_end, num_pages, pg, map_properties, OperationType_MapGroup, false));
+
+            /* We succeeded, so commit our memory reservation. */
+            memory_reservation.Commit();
+
+            /* Apply the memory block update. */
+            this->memory_block_manager.Update(std::addressof(allocator), this->current_heap_end, num_pages, KMemoryState_Normal, KMemoryPermission_UserReadWrite, KMemoryAttribute_None);
+
+            /* Update the current heap end. */
+            this->current_heap_end = this->heap_region_start + size;
+
+            /* Set the output. */
+            *out = this->heap_region_start;
+            return ResultSuccess();
+        }
     }
 
     Result KPageTableBase::SetMaxHeapSize(size_t size) {
diff --git a/libraries/libmesosphere/source/svc/kern_svc_physical_memory.cpp b/libraries/libmesosphere/source/svc/kern_svc_physical_memory.cpp
index c7cb9a7c6..07e1f136e 100644
--- a/libraries/libmesosphere/source/svc/kern_svc_physical_memory.cpp
+++ b/libraries/libmesosphere/source/svc/kern_svc_physical_memory.cpp
@@ -21,6 +21,20 @@ namespace ams::kern::svc {
 
     namespace {
 
+        Result SetHeapSize(uintptr_t *out_address, size_t size) {
+            /* Validate size. */
+            R_UNLESS(util::IsAligned(size, ams::svc::HeapSizeAlignment), svc::ResultInvalidSize());
+            R_UNLESS(size < ams::kern::MainMemorySize,                   svc::ResultInvalidSize());
+
+            /* Set the heap size. */
+            KProcessAddress address;
+            R_TRY(GetCurrentProcess().GetPageTable().SetHeapSize(std::addressof(address), size));
+
+            /* Set the output. */
+            *out_address = GetInteger(address);
+            return ResultSuccess();
+        }
+
         Result SetUnsafeLimit(size_t limit) {
             /* Ensure the size is aligned. */
             R_UNLESS(util::IsAligned(limit, PageSize), svc::ResultInvalidSize());
@@ -37,7 +51,8 @@ namespace ams::kern::svc {
     /* =============================    64 ABI    ============================= */
 
     Result SetHeapSize64(ams::svc::Address *out_address, ams::svc::Size size) {
-        MESOSPHERE_PANIC("Stubbed SvcSetHeapSize64 was called.");
+        static_assert(sizeof(*out_address) == sizeof(uintptr_t));
+        return SetHeapSize(reinterpret_cast<uintptr_t *>(out_address), size);
     }
 
     Result MapPhysicalMemory64(ams::svc::Address address, ams::svc::Size size) {
@@ -63,7 +78,8 @@ namespace ams::kern::svc {
     /* ============================= 64From32 ABI ============================= */
 
     Result SetHeapSize64From32(ams::svc::Address *out_address, ams::svc::Size size) {
-        MESOSPHERE_PANIC("Stubbed SvcSetHeapSize64From32 was called.");
+        static_assert(sizeof(*out_address) == sizeof(uintptr_t));
+        return SetHeapSize(reinterpret_cast<uintptr_t *>(out_address), size);
     }
 
     Result MapPhysicalMemory64From32(ams::svc::Address address, ams::svc::Size size) {
diff --git a/libraries/libvapours/include/vapours/svc/svc_types_common.hpp b/libraries/libvapours/include/vapours/svc/svc_types_common.hpp
index 48e7941de..bf4530a64 100644
--- a/libraries/libvapours/include/vapours/svc/svc_types_common.hpp
+++ b/libraries/libvapours/include/vapours/svc/svc_types_common.hpp
@@ -116,6 +116,8 @@ namespace ams::svc {
         MemoryAttribute_Uncached     = (1 << 3),
     };
 
+    constexpr inline size_t HeapSizeAlignment = 2_MB;
+
     struct PageInfo {
         u32 flags;
     };