[PATCH 063/104] KVM: VMX: Split segments reload in vmx_load_host_state()

Avi Kivity
2007-09-17T08:47:32Z

From: Laurent Vivier <Laurent.Vivier@bull.net>

vmx_load_host_state() bundles fs, gs, ldt, and tss reloading into
one in the hope that it is infrequent. With smp guests, fs reloading is
frequent due to fs being used by threads.

Unbundle the reloads so reduce expensive gs reloads.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
drivers/kvm/vmx.c | 22 ++++++++++++----------
1 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index b400668..d63e82e 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -54,7 +54,8 @@ struct vcpu_vmx {
struct {
int loaded;
u16 fs_sel, gs_sel, ldt_sel;
- int fs_gs_ldt_reload_needed;
+ int gs_ldt_reload_needed;
+ int fs_reload_needed;
}host_state;

};
@@ -353,20 +354,21 @@ static void vmx_save_host_state(struct vcpu_vmx *vmx)
* allow segment selectors with cpl > 0 or ti == 1.
*/
vmx->host_state.ldt_sel = read_ldt();
- vmx->host_state.fs_gs_ldt_reload_needed = vmx->host_state.ldt_sel;
+ vmx->host_state.gs_ldt_reload_needed = vmx->host_state.ldt_sel;
vmx->host_state.fs_sel = read_fs();
- if (!(vmx->host_state.fs_sel & 7))
+ if (!(vmx->host_state.fs_sel & 7)) {
vmcs_write16(HOST_FS_SELECTOR, vmx->host_state.fs_sel);
- else {
+ vmx->host_state.fs_reload_needed = 0;
+ } else {
vmcs_write16(HOST_FS_SELECTOR, 0);
- vmx->host_state.fs_gs_ldt_reload_needed = 1;
+ vmx->host_state.fs_reload_needed = 1;
}
vmx->host_state.gs_sel = read_gs();
if (!(vmx->host_state.gs_sel & 7))
vmcs_write16(HOST_GS_SELECTOR, vmx->host_state.gs_sel);
else {
vmcs_write16(HOST_GS_SELECTOR, 0);
- vmx->host_state.fs_gs_ldt_reload_needed = 1;
+ vmx->host_state.gs_ldt_reload_needed = 1;
}

#ifdef CONFIG_X86_64
@@ -396,9 +398,10 @@ static void vmx_load_host_state(struct vcpu_vmx *vmx)
return;

vmx->host_state.loaded = 0;
- if (vmx->host_state.fs_gs_ldt_reload_needed) {
- load_ldt(vmx->host_state.ldt_sel);
+ if (vmx->host_state.fs_reload_needed)
load_fs(vmx->host_state.fs_sel);
+ if (vmx->host_state.gs_ldt_reload_needed) {
+ load_ldt(vmx->host_state.ldt_sel);
/*
* If we have to reload gs, we must take care to
* preserve our gs base.
@@ -409,9 +412,8 @@ static void vmx_load_host_state(struct vcpu_vmx *vmx)
wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
#endif
local_irq_restore(flags);
-
- reload_tss();
}
+ reload_tss();
save_msrs(vmx->guest_msrs, vmx->save_nmsrs);
load_msrs(vmx->host_msrs, vmx->save_nmsrs);
if (msr_efer_need_save_restore(vmx))
--
1.5.3