linux-kernel - Re: [PATCH 2/3] kvm mmu: remove redundant check in mmu_set

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Message-ID: <20090218183808.GE25719@amt.cnet>
Date:	Wed, 18 Feb 2009 15:38:08 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] kvm mmu: remove redundant check in mmu_set_spte


The following code flow is unnecessary:

	if (largepage)
		was_rmapped = is_large_pte(*shadow_pte);
	 else
	 	was_rmapped = 1;

The is_large_pte() function will always evaluate to one here because the
(largepage && !is_large_pte) case is already handled in the first
if-clause. So we can remove this check and set was_rmapped to one always
here.

Signed-off-by: Joerg Roedel <joerg.roedel@....com>
Acked-by: Marcelo Tosatti <mtosatti@...hat.com>

---
 arch/x86/kvm/mmu.c |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ef060ec..c90b4b2 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1791,12 +1791,8 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
 			pgprintk("hfn old %lx new %lx\n",
 				 spte_to_pfn(*shadow_pte), pfn);
 			rmap_remove(vcpu->kvm, shadow_pte);
-		} else {
-			if (largepage)
-				was_rmapped = is_large_pte(*shadow_pte);
-			else
-				was_rmapped = 1;
-		}
+		} else
+			was_rmapped = 1;
 	}
 	if (set_spte(vcpu, shadow_pte, pte_access, user_fault, write_fault,
 		      dirty, largepage, global, gfn, pfn, speculative, true)) {
--
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