linux-kernel - [PATCH resend 1/2] KVM: arm64: Clean up the checking for huge mapping

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Date:   Thu, 7 May 2020 20:35:45 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <kvmarm@...ts.cs.columbia.edu>, <suzuki.poulose@....com>
CC:     <maz@...nel.org>, <christoffer.dall@....com>,
        <james.morse@....com>, <julien.thierry.kdev@...il.com>,
        <kvm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <wanghaibin.wang@...wei.com>,
        <zhengxiang9@...wei.com>, <amurray@...goodpenguin.co.uk>,
        <eric.auger@...hat.com>, Zenghui Yu <yuzenghui@...wei.com>
Subject: [PATCH resend 1/2] KVM: arm64: Clean up the checking for huge mapping

From: Suzuki K Poulose <suzuki.poulose@....com>

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.

While we're at it, fixup a typo in the comment below.

Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <maz@...nel.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
---
 virt/kvm/arm/mmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index e3b9ee268823..557f36866d1c 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1607,6 +1607,10 @@ 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;
@@ -1626,7 +1630,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
 	 *    |abcde|fgh  Stage-1 block  |    Stage-1 block tv|xyz|
 	 *    +-----+--------------------+--------------------+---+
 	 *
-	 *    memslot->base_gfn << PAGE_SIZE:
+	 *    memslot->base_gfn << PAGE_SHIFT:
 	 *      +---+--------------------+--------------------+-----+
 	 *      |abc|def  Stage-2 block  |    Stage-2 block   |tvxyz|
 	 *      +---+--------------------+--------------------+-----+
-- 
2.19.1