linux-kernel - [PATCH 1/2] kvm: arm: Clean up the checking for huge mapping

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Date:   Wed, 10 Apr 2019 16:23:51 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, julien.thierry@....com,
        christoffer.dall@....com, marc.zyngier@....com,
        andrew.murray@....com, eric.auger@...hat.com,
        zhengxiang9@...wei.com, yuzenghui@...wei.com,
        wanghaibin.wang@...wei.com,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH 1/2] kvm: arm: Clean up the checking for huge mapping

If we are checking whether the stage2 can map PAGE_SIZE,
we don't have to do the boundary checks as both the host
VMA and the guest memslots are page aligned. Bail the case
easily.

Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 virt/kvm/arm/mmu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index a39dcfd..6d73322 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1624,6 +1624,10 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
 	hva_t uaddr_start, uaddr_end;
 	size_t size;
 
+	/* The memslot and the VMA are guaranteed to be aligned to PAGE_SIZE */
+	if (map_size == PAGE_SIZE)
+		return true;
+
 	size = memslot->npages * PAGE_SIZE;
 
 	gpa_start = memslot->base_gfn << PAGE_SHIFT;
-- 
2.7.4