From: Babu Moger <babu.moger@amd.com>
Date: Fri, 16 Mar 2018 16:37:23 -0400
Subject: KVM: VMX: Remove ple_window_actual_max
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Git-commit: 18abdc3425aa546424672d3b1f932ecc55132368
Patch-mainline: v4.17-rc1
References: fate#325533
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@redhat.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
[Fixed potential wraparound and change the max to UINT_MAX. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/kvm/vmx.c | 31 ++++++-------------------------
1 file changed, 6 insertions(+), 25 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4eb252b13121..7a92e2e1ea2e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -172,8 +172,7 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO);
#define KVM_VMX_DEFAULT_PLE_WINDOW 4096
#define KVM_VMX_DEFAULT_PLE_WINDOW_GROW 2
#define KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK 0
-#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX \
- INT_MAX / KVM_VMX_DEFAULT_PLE_WINDOW_GROW
+#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX UINT_MAX
static unsigned int ple_gap = KVM_VMX_DEFAULT_PLE_GAP;
module_param(ple_gap, uint, 0444);
@@ -190,7 +189,6 @@ static unsigned int ple_window_shrink = KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK;
module_param(ple_window_shrink, uint, 0444);
/* Default is to compute the maximum so we can never overflow. */
-static unsigned int ple_window_actual_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
static unsigned int ple_window_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
module_param(ple_window_max, uint, 0444);
@@ -6986,17 +6984,17 @@ out:
static unsigned int __grow_ple_window(unsigned int val)
{
+ u64 ret = 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;
+ ret *= ple_window_grow;
else
- val += ple_window_grow;
+ ret += ple_window_grow;
- return val;
+ return min(ret, (u64)ple_window_max);
}
static unsigned int __shrink_ple_window(unsigned int val,
@@ -7041,21 +7039,6 @@ 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)
@@ -7175,8 +7158,6 @@ 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.