From: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [PATCH 12/18] KVM: VMX: Only save/restore MSR_K6_STAR if necessary
Date: Thu, 26 Apr 2007 12:22:12 +0300 [thread overview]
Message-ID: <11775793381764-git-send-email-avi@qumranet.com> (raw)
In-Reply-To: <11775793382353-git-send-email-avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
Intel hosts only support syscall/sysret in long more (and only if efer.sce
is enabled), so only reload the related MSR_K6_STAR if the guest will
actually be able to use it.
This reduces vmexit cost by about 500 cycles (6400 -> 5870) on my setup.
Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
drivers/kvm/vmx.c | 16 ++++++++++++++++
1 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index b61d4dd..37537af 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -69,6 +69,10 @@ static struct kvm_vmx_segment_field {
VMX_SEGMENT_FIELD(LDTR),
};
+/*
+ * Keep MSR_K6_STAR at the end, as setup_msrs() will try to optimize it
+ * away by decrementing the array size.
+ */
static const u32 vmx_msr_index[] = {
#ifdef CONFIG_X86_64
MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR, MSR_KERNEL_GS_BASE,
@@ -323,6 +327,18 @@ static void setup_msrs(struct kvm_vcpu *vcpu)
nr_skip = NR_64BIT_MSRS;
nr_good_msrs = vcpu->nmsrs - nr_skip;
+ /*
+ * MSR_K6_STAR is only needed on long mode guests, and only
+ * if efer.sce is enabled.
+ */
+ if (find_msr_entry(vcpu, MSR_K6_STAR)) {
+ --nr_good_msrs;
+#ifdef CONFIG_X86_64
+ if (is_long_mode(vcpu) && (vcpu->shadow_efer & EFER_SCE))
+ ++nr_good_msrs;
+#endif
+ }
+
vmcs_writel(VM_ENTRY_MSR_LOAD_ADDR,
virt_to_phys(vcpu->guest_msrs + nr_skip));
vmcs_writel(VM_EXIT_MSR_STORE_ADDR,
--
1.5.0.6
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next prev parent reply other threads:[~2007-04-26 9:22 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-26 9:22 [PATCH 00/18] KVM updates for 2.6.22 Avi Kivity
2007-04-26 9:22 ` [PATCH 02/18] KVM: Fix overflow bug in overflow detection code Avi Kivity
2007-04-26 9:22 ` [PATCH 03/18] KVM: Initialize cr0 to indicate an fpu is present Avi Kivity
2007-04-26 9:22 ` [PATCH 04/18] KVM: Handle partial pae pdptr Avi Kivity
[not found] ` <11775793382353-git-send-email-avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2007-04-26 9:22 ` [PATCH 01/18] KVM: Use kernel-standard types Avi Kivity
2007-04-26 9:22 ` [PATCH 05/18] KVM: Use slab caches to allocate mmu data structures Avi Kivity
2007-04-26 9:22 ` [PATCH 06/18] KVM: Retry sleeping allocation if atomic allocation fails Avi Kivity
2007-04-26 9:22 ` [PATCH 07/18] KVM: SVM: Report hardware exit reason to userspace instead of dmesg Avi Kivity
2007-04-26 9:22 ` [PATCH 08/18] KVM: Handle guest page faults when emulating mmio Avi Kivity
2007-04-26 9:22 ` [PATCH 09/18] KVM: VMX: Reduce unnecessary saving of host msrs Avi Kivity
2007-04-26 9:22 ` [PATCH 10/18] KVM: VMX: Don't switch 64-bit msrs for 32-bit guests Avi Kivity
2007-04-26 9:22 ` [PATCH 11/18] KVM: Fold drivers/kvm/kvm_vmx.h into drivers/kvm/vmx.c Avi Kivity
2007-04-26 9:22 ` Avi Kivity [this message]
2007-04-26 9:22 ` [PATCH 13/18] KVM: MMU: Avoid heavy ASSERT at non debug mode Avi Kivity
2007-04-26 9:22 ` [PATCH 14/18] KVM: VMX: Avoid unnecessary vcpu_load()/vcpu_put() cycles Avi Kivity
2007-04-26 9:22 ` [PATCH 15/18] KVM: Per-vcpu statistics Avi Kivity
2007-04-26 9:22 ` [PATCH 16/18] KVM: Allow passing 64-bit values to the emulated read/write API Avi Kivity
2007-04-26 9:22 ` [PATCH 17/18] KVM: Lazy FPU support for SVM Avi Kivity
2007-04-26 9:22 ` [PATCH 18/18] KVM: Don't complain about cpu erratum AA15 Avi Kivity
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