From: Himadri Pandya <himadrispandya@gmail.com>
Date: Tue, 30 Jul 2019 09:49:43 +0000
Patch-mainline: v5.5-rc1
Subject: x86: hv: Add function to allocate zeroed page for Hyper-V
Git-commit: fa36dcdf8b200f4c175d0a00a8c99439ee0df95d
References: jsc#sle-12891

Hyper-V assumes page size to be 4K. While this assumption holds true on
x86 architecture, it might not  be true for ARM64 architecture. Hence
define hyper-v specific function to allocate a zeroed page which can
have a different implementation on ARM64 architecture to handle the
conflict between hyper-v's assumed page size and actual guest page size.

Signed-off-by: Himadri Pandya <himadri18.07@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Olaf Hering <ohering@suse.de>
---
 arch/x86/hyperv/hv_init.c       | 8 ++++++++
 arch/x86/include/asm/mshyperv.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -45,6 +45,14 @@ void *hv_alloc_hyperv_page(void)
 }
 EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
 
+void *hv_alloc_hyperv_zeroed_page(void)
+{
+        BUILD_BUG_ON(PAGE_SIZE != HV_HYP_PAGE_SIZE);
+
+        return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
+
 void hv_free_hyperv_page(unsigned long addr)
 {
 	free_page(addr);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -219,6 +219,7 @@ static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)
 void __init hyperv_init(void);
 void hyperv_setup_mmu_ops(void);
 void *hv_alloc_hyperv_page(void);
+void *hv_alloc_hyperv_zeroed_page(void);
 void hv_free_hyperv_page(unsigned long addr);
 void hyperv_reenlightenment_intr(struct pt_regs *regs);
 void set_hv_tscchange_cb(void (*cb)(void));