linux-kernel - [PATCH v2 2/5] KVM: VMX: Remove ple_window_actual

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 16 Mar 2018 16:37:23 -0400
From:   Babu Moger <babu.moger@....com>
To:     joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        babu.moger@....com
Subject: [PATCH v2 2/5] KVM: VMX: Remove ple_window_actual_max

Get rid of ple_window_actual_max, because its benefits are really
minuscule and the logic is complicated.

The overflows(and underflow) are controlled in __ple_window_grow
and _ple_window_shrink respectively.

Suggested-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Babu Moger <babu.moger@....com>
---
 arch/x86/kvm/vmx.c | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c9a9080..b992d81 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -178,7 +178,6 @@
 module_param(ple_window_shrink, uint, 0444);
 
 /* Default is to compute the maximum so we can never overflow. */
-static uint ple_window_actual_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
 static uint ple_window_max        = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
 module_param(ple_window_max, uint, 0444);
 
@@ -6645,14 +6644,12 @@ static uint __grow_ple_window(uint val)
 	if (ple_window_grow < 1)
 		return ple_window;
 
-	val = min(val, ple_window_actual_max);
-
 	if (ple_window_grow < ple_window)
 		val *= ple_window_grow;
 	else
 		val += ple_window_grow;
 
-	return val;
+	return min(val, ple_window_max);
 }
 
 static uint __shrink_ple_window(uint val, uint modifier, uint minimum)
@@ -6696,21 +6693,6 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)
 }
 
 /*
- * ple_window_actual_max is computed to be one grow_ple_window() below
- * ple_window_max. (See __grow_ple_window for the reason.)
- * This prevents overflows, because ple_window_max is int.
- * ple_window_max effectively rounded down to a multiple of ple_window_grow in
- * this process.
- * ple_window_max is also prevented from setting vmx->ple_window < ple_window.
- */
-static void update_ple_window_actual_max(void)
-{
-	ple_window_actual_max =
-			__shrink_ple_window(max(ple_window_max, ple_window),
-			                    ple_window_grow, INT_MIN);
-}
-
-/*
  * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
  */
 static void wakeup_handler(void)
@@ -6876,8 +6858,6 @@ static __init int hardware_setup(void)
 	else
 		kvm_disable_tdp();
 
-	update_ple_window_actual_max();
-
 	/*
 	 * Only enable PML when hardware supports PML feature, and both EPT
 	 * and EPT A/D bit features are enabled -- PML depends on them to work.
-- 
1.8.3.1