[PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages

[Michael Kelley]

Add ARM64-specific code to allocate memory with HV_HYP_PAGE_SIZE
size and alignment. These are for use when pages need to be shared
with Hyper-V. Separate functions are needed as the page size used
by Hyper-V may not be the same as the guest page size.

This code is built only when CONFIG_HYPERV is enabled.

Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
 arch/arm64/hyperv/hv_core.c    | 34 ++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h |  5 +++++
 2 files changed, 39 insertions(+)

diff --git a/arch/arm64/hyperv/hv_core.c b/arch/arm64/hyperv/hv_core.c
index 272c348..4aa6b8f 100644
--- a/arch/arm64/hyperv/hv_core.c
+++ b/arch/arm64/hyperv/hv_core.c
@@ -17,12 +17,46 @@
 #include <linux/slab.h>
 #include <linux/hyperv.h>
 #include <linux/arm-smccc.h>
+#include <linux/string.h>
 #include <asm-generic/bug.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
 
 
 /*
+ * Functions for allocating and freeing memory with size and
+ * alignment HV_HYP_PAGE_SIZE. These functions are needed because
+ * the guest page size may not be the same as the Hyper-V page
+ * size. We depend upon kmalloc() aligning power-of-two size
+ * allocations to the allocation size boundary, so that the
+ * allocated memory appears to Hyper-V as a page of the size
+ * it expects.
+ *
+ * These functions are used by arm64 specific code as well as
+ * arch independent Hyper-V drivers.
+ */
+
+void *hv_alloc_hyperv_page(void)
+{
+	BUILD_BUG_ON(PAGE_SIZE <  HV_HYP_PAGE_SIZE);
+	return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
+
+void *hv_alloc_hyperv_zeroed_page(void)
+{
+	return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
+
+void hv_free_hyperv_page(unsigned long addr)
+{
+	kfree((void *)addr);
+}
+EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
+
+
+/*
  * hv_do_hypercall- Invoke the specified hypercall
  */
 u64 hv_do_hypercall(u64 control, void *input, void *output)
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index b3f1082..1a7c4c5 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -99,6 +99,11 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
 void hv_remove_crash_handler(void);
 
+void *hv_alloc_hyperv_page(void);
+void *hv_alloc_hyperv_zeroed_page(void);
+void hv_free_hyperv_page(unsigned long addr);
+
+
 #if IS_ENABLED(CONFIG_HYPERV)
 /*
  * Hypervisor's notion of virtual processor ID is different from
-- 
1.8.3.1