linux-kernel - [PATCH 063/104] KVM: VMX: Split segments reload in vmx_load_host

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]

Message-Id: <11900179483059-git-send-email-avi@qumranet.com>
Date:	Mon, 17 Sep 2007 10:31:45 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org,
	Laurent Vivier <Laurent.Vivier@...l.net>
Subject: [PATCH 063/104] KVM: VMX: Split segments reload in vmx_load_host_state()

From: Laurent Vivier <Laurent.Vivier@...l.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@...l.net>
Signed-off-by: Avi Kivity <avi@...ranet.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

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/