[PATCH 1/2] accel/hvf: introduce map granule abstraction

[Lucas Amaral <lucaaamaral@gmail.com>]

Replace hardcoded qemu_real_host_page_size() calls in HVF memory
mapping with a configurable map granule (hvf_set/get_map_granule).

On macOS ARM64, the host page size is 16KB, but the guest kernel
typically uses 4KB pages.  The map granule determines the minimum
alignment for hv_vm_map() and hv_vm_protect().

Default behavior is unchanged (returns host page size).  A subsequent
commit will configure 4KB granule on macOS 26+.

Also fix the non-aligned region path in hvf_set_phys_mem() to return
early instead of proceeding with add=false, which would attempt an
unnecessary unmap of a region that was never mapped.

Signed-off-by: Lucas Amaral <lucaaamaral@gmail.com>
---
 accel/hvf/hvf-all.c  | 21 ++++++++++++++++++---
 include/system/hvf.h | 15 +++++++++++++++
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/accel/hvf/hvf-all.c b/accel/hvf/hvf-all.c
index 033c677..ccff626 100644
--- a/accel/hvf/hvf-all.c
+++ b/accel/hvf/hvf-all.c
@@ -23,6 +23,21 @@
 
 bool hvf_allowed;
 
+static uint64_t hvf_map_granule;
+
+void hvf_set_map_granule(uint64_t size)
+{
+    hvf_map_granule = size;
+}
+
+uint64_t hvf_get_map_granule(void)
+{
+    if (!hvf_map_granule) {
+        return qemu_real_host_page_size();
+    }
+    return hvf_map_granule;
+}
+
 const char *hvf_return_string(hv_return_t ret)
 {
     switch (ret) {
@@ -54,7 +69,7 @@ void assert_hvf_ok_impl(hv_return_t ret, const char *file, unsigned int line,
 static void do_hv_vm_protect(hwaddr start, size_t size,
                              hv_memory_flags_t flags)
 {
-    intptr_t page_mask = qemu_real_host_page_mask();
+    intptr_t page_mask = -(intptr_t)hvf_get_map_granule();
     hv_return_t ret;
 
     trace_hvf_vm_protect(start, size, flags,
@@ -84,7 +99,7 @@ static void hvf_set_phys_mem(MemoryRegionSection *section, bool add)
     MemoryRegion *area = section->mr;
     bool writable = !area->readonly && !area->rom_device;
     hv_memory_flags_t flags;
-    uint64_t page_size = qemu_real_host_page_size();
+    uint64_t page_size = hvf_get_map_granule();
     uint64_t gpa = section->offset_within_address_space;
     uint64_t size = int128_get64(section->size);
     hv_return_t ret;
@@ -105,7 +120,7 @@ static void hvf_set_phys_mem(MemoryRegionSection *section, bool add)
     if (!QEMU_IS_ALIGNED(size, page_size) ||
         !QEMU_IS_ALIGNED(gpa, page_size)) {
         /* Not page aligned, so we can not map as RAM */
-        add = false;
+        return;
     }
 
     if (!add) {
diff --git a/include/system/hvf.h b/include/system/hvf.h
index d3dcf08..d1b702b 100644
--- a/include/system/hvf.h
+++ b/include/system/hvf.h
@@ -36,4 +36,19 @@ typedef struct HVFState HVFState;
 DECLARE_INSTANCE_CHECKER(HVFState, HVF_STATE,
                          TYPE_HVF_ACCEL)
 
+#ifdef CONFIG_HVF_IS_POSSIBLE
+/*
+ * Minimum alignment for hv_vm_map(). Returns host page size (16KB on
+ * macOS ARM64), or 4KB when HVF 4KB IPA granule is configured (macOS 26+).
+ */
+void hvf_set_map_granule(uint64_t size);
+uint64_t hvf_get_map_granule(void);
+#else
+static inline void hvf_set_map_granule(uint64_t size) {}
+static inline uint64_t hvf_get_map_granule(void)
+{
+    return qemu_real_host_page_size();
+}
+#endif
+
 #endif
-- 
2.52.0