[PATCH] Split segments reload in vmx_load_host_state()

[Laurent Vivier <Laurent.Vivier-6ktuUTfB/bM@public.gmane.org>]

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It is from the TODO and I hope no one is already working on this.

'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 and the
separate reloads should be unbundled.'

Signed-off-by: Laurent Vivier <Laurent.Vivier-6ktuUTfB/bM@public.gmane.org>

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Index: kvm/drivers/kvm/vmx.c
===================================================================
--- kvm.orig/drivers/kvm/vmx.c	2007-08-23 11:26:34.000000000 +0200
+++ kvm/drivers/kvm/vmx.c	2007-08-23 13:45:10.000000000 +0200
@@ -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 +354,20 @@ static void vmx_save_host_state(struct v
 	 * 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))
 		vmcs_write16(HOST_FS_SELECTOR, vmx->host_state.fs_sel);
 	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 +397,10 @@ static void vmx_load_host_state(struct v
 		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 +411,9 @@ static void vmx_load_host_state(struct v
 		wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
 #endif
 		local_irq_restore(flags);
-
-		reload_tss();
 	}
+	if (vmx->host_state.gs_ldt_reload_needed || vmx->host_state.fs_reload_needed)
+		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))

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