[PATCH] arm64: tlb: Fix TLBI RANGE operand

[Gavin Shan]

KVM/arm64 relies on TLBI RANGE feature to flush TLBs when the dirty
bitmap is collected by VMM and the corresponding PTEs need to be
write-protected again. Unfortunately, the operand passed to the TLBI
RANGE instruction isn't correctly sorted out by commit d1d3aa98b1d4
("arm64: tlb: Use the TLBI RANGE feature in arm64"). It leads to
crash on the destination VM after live migration because some of the
dirty pages are missed.

For example, I have a VM where 8GB memory is assigned, starting from
0x40000000 (1GB). Note that the host has 4KB as the base page size.
All TLBs for VM can be covered by one TLBI RANGE operation. However,
I receives 0xffff708000040000 as the operand, which is wrong and the
correct one should be 0x00007f8000040000. From the wrong operand, we
have 3 and 1 for SCALE (bits[45:44) and NUM (bits943:39], only 1GB
instead of 8GB memory is covered.

Fix the macro __TLBI_RANGE_NUM() so that the correct NUM and TLBI
RANGE operand are provided.

Fixes: d1d3aa98b1d4 ("arm64: tlb: Use the TLBI RANGE feature in arm64")
Cc: stable at kernel.org # v5.10+
Reported-by: Yihuang Yu <yihyu at redhat.com>
Signed-off-by: Gavin Shan <gshan at redhat.com>
---
 arch/arm64/include/asm/tlbflush.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index 3b0e8248e1a4..07c4fb4b82b4 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -166,7 +166,7 @@ static inline unsigned long get_trans_granule(void)
  */
 #define TLBI_RANGE_MASK			GENMASK_ULL(4, 0)
 #define __TLBI_RANGE_NUM(pages, scale)	\
-	((((pages) >> (5 * (scale) + 1)) & TLBI_RANGE_MASK) - 1)
+	((((pages) >> (5 * (scale) + 1)) - 1) & TLBI_RANGE_MASK)
 
 /*
  *	TLB Invalidation
-- 
2.44.0