[PATCH] KVM: arm/arm64: Revert to old way of checking for device mapping in stage2_flush_ptes().

[Pavel Fedin <p.fedin@samsung.com>]

This function takes stage-II physical addresses (A.K.A. IPA), on input, not
real physical addresses. This causes kvm_is_device_pfn() to return wrong
values, depending on how much guest and host memory maps match. This
results in completely broken KVM on some boards. The problem has been
caught on Samsung proprietary hardware.

Cc: stable@vger.kernel.org
Fixes: e6fab5442345 ("ARM/arm64: KVM: test properly for a PTE's uncachedness")

Signed-off-by: Pavel Fedin <p.fedin@samsung.com>
---
 arch/arm/kvm/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 7dace90..51ad98f 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -310,7 +310,8 @@ static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
 
 	pte = pte_offset_kernel(pmd, addr);
 	do {
-		if (!pte_none(*pte) && !kvm_is_device_pfn(__phys_to_pfn(addr)))
+		if (!pte_none(*pte) &&
+		    (pte_val(*pte) & PAGE_S2_DEVICE) != PAGE_S2_DEVICE)
 			kvm_flush_dcache_pte(*pte);
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }
-- 
2.4.4