[PATCH v2] x86/hyperv: Remove BUG_ON() for kmap_local_page()

* [PATCH v2] x86/hyperv: Remove BUG_ON() for kmap_local_page()
@ 2022-10-20  8:38 Zhao Liu
  2022-10-26 15:17 ` Wei Liu
  0 siblings, 1 reply; 4+ messages in thread
From: Zhao Liu @ 2022-10-20  8:38 UTC (permalink / raw)
  To: K . Y . Srinivasan, Haiyang Zhang, Stephen Hemminger, Wei Liu,
	Dexuan Cui, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	Dave Hansen, x86, H . Peter Anvin, linux-hyperv, linux-kernel
  Cc: Ira Weiny, Fabio M . De Francesco, Zhenyu Wang, Zhao Liu

From: Zhao Liu <zhao1.liu@intel.com>

The commit 154fb14df7a3c ("x86/hyperv: Replace kmap() with
kmap_local_page()") keeps the BUG_ON() to check if kmap_local_page()
fails.

But in fact, kmap_local_page() always returns a valid kernel address
and won't return NULL here. It will BUG on its own if it fails. [1]

So directly use memcpy_to_page() which creates local mapping to copy.

[1]: https://lore.kernel.org/lkml/YztFEyUA48et0yTt@iweiny-mobl/

Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Change in v2:
 - Removed "Fixes" tag in patch message.
---
 arch/x86/hyperv/hv_init.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 29774126e931..f66c5709324f 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -459,13 +459,11 @@ void __init hyperv_init(void)
 		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 
 		pg = vmalloc_to_page(hv_hypercall_pg);
-		dst = kmap_local_page(pg);
 		src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE,
 				MEMREMAP_WB);
-		BUG_ON(!(src && dst));
-		memcpy(dst, src, HV_HYP_PAGE_SIZE);
+		BUG_ON(!src);
+		memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE);
 		memunmap(src);
-		kunmap_local(dst);
 	} else {
 		hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
 		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
-- 
2.34.1


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