linux-kernel - Re: [PATCH] KVM: SVM: Do not issue virtual VMLOAD/VMSAVE supported-message

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Date:   Wed, 6 Sep 2017 15:17:36 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     KVM <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: SVM: Do not issue virtual VMLOAD/VMSAVE
 supported-message

On Wed, Sep 06, 2017 at 02:54:05PM +0200, David Hildenbrand wrote:
> Maybe go one step further and incorporate everything (+vls) into a
> single if statement?

Or maybe simplify it even more by not even looking at vls. If the user
disables it, fine, if she enables it but the hw doesn't support it, it
will be set to false automatically.

Or am I missing a case?

---
From: Borislav Petkov <bp@...e.de>
Date: Tue, 5 Sep 2017 18:59:55 +0200
Subject: [PATCH] KVM: SVM: Do not issue virtual VMLOAD/VMSAVE
 supported-message
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

There's no need to issue that everytime during boot - we have the
/proc/cpuinfo flag for people and software to query.

Also, simplify logic which verifies the vls chicken bit setting.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: David Hildenbrand <david@...hat.com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/svm.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8dbd8dbc83eb..d3c481778d9c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1098,15 +1098,10 @@ static __init int svm_hardware_setup(void)
 		}
 	}
 
-	if (vls) {
-		if (!npt_enabled ||
-		    !boot_cpu_has(X86_FEATURE_V_VMSAVE_VMLOAD) ||
-		    !IS_ENABLED(CONFIG_X86_64)) {
-			vls = false;
-		} else {
-			pr_info("Virtual VMLOAD VMSAVE supported\n");
-		}
-	}
+	if (!npt_enabled ||
+	    !boot_cpu_has(X86_FEATURE_V_VMSAVE_VMLOAD) ||
+	    !IS_ENABLED(CONFIG_X86_64))
+		vls = false;
 
 	return 0;
 
-- 
2.13.0

-- 
Regards/Gruss,
    Boris.

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