linux-kernel - Re: [PATCH 05/47] KVM: VMX: Optimize vmx_get

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Message-ID: <4A95437C.2060707@gmail.com>
Date:	Wed, 26 Aug 2009 16:15:24 +0200
From:	Roel Kluin <roel.kluin@...il.com>
To:	Avi Kivity <avi@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/47] KVM: VMX: Optimize vmx_get_cpl()

Op 26-08-09 12:29, Avi Kivity schreef:
> Instead of calling vmx_get_segment() (which reads a whole bunch of
> vmcs fields), read only the cs selector which contains the cpl.
> 
> Signed-off-by: Avi Kivity <avi@...hat.com>

Can't we also optimise cs_ss_rpl_check()? (Please review, untested.)

------------- >8 ---------------------- 8< --------------------
Instead of calling vmx_get_segment() (which reads a whole bunch of
vmcs fields), read only the cs/ss selectors which contains the rpls.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
---
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 29f9129..5d8512a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1932,13 +1932,8 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
 
 static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
 {
-	struct kvm_segment cs, ss;
-
-	vmx_get_segment(vcpu, &cs, VCPU_SREG_CS);
-	vmx_get_segment(vcpu, &ss, VCPU_SREG_SS);
-
-	return ((cs.selector & SELECTOR_RPL_MASK) ==
-		 (ss.selector & SELECTOR_RPL_MASK));
+	return ((vmcs_read16(GUEST_CS_SELECTOR) & SELECTOR_RPL_MASK) ==
+		 (vmcs_read16(GUEST_SS_SELECTOR) & SELECTOR_RPL_MASK));
 }
 
 /*
--
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