lkml.org 
[lkml]   [2007]   [Mar]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[patch] KVM: always reload segment selectors
Subject: [patch] KVM: always reload segment selectors
From: Ingo Molnar <mingo@elte.hu>

failed VM entry on VMX might still change %fs or %gs, thus make sure
that KVM always reloads the segment selectors. This is crutial on both
x86 and x86_64: x86 has __KERNEL_PDA in %fs on which things like
'current' depends and x86_64 has 0 there and needs MSR_GS_BASE to work.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
drivers/kvm/vmx.c | 37 +++++++++++++++++++++----------------
1 file changed, 21 insertions(+), 16 deletions(-)

Index: linux/drivers/kvm/vmx.c
===================================================================
--- linux.orig/drivers/kvm/vmx.c
+++ linux/drivers/kvm/vmx.c
@@ -1896,6 +1896,27 @@ again:
[cr2]"i"(offsetof(struct kvm_vcpu, cr2))
: "cc", "memory" );

+ /*
+ * Reload segment selectors ASAP. (it's needed for a functional
+ * kernel: x86 relies on having __KERNEL_PDA in %fs and x86_64
+ * relies on having 0 in %gs for the CPU PDA to work.)
+ */
+ if (fs_gs_ldt_reload_needed) {
+ load_ldt(ldt_sel);
+ load_fs(fs_sel);
+ /*
+ * If we have to reload gs, we must take care to
+ * preserve our gs base.
+ */
+ local_irq_disable();
+ load_gs(gs_sel);
+#ifdef CONFIG_X86_64
+ wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
+#endif
+ local_irq_enable();
+
+ reload_tss();
+ }
++kvm_stat.exits;

save_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
@@ -1913,22 +1934,6 @@ again:
kvm_run->exit_reason = vmcs_read32(VM_INSTRUCTION_ERROR);
r = 0;
} else {
- if (fs_gs_ldt_reload_needed) {
- load_ldt(ldt_sel);
- load_fs(fs_sel);
- /*
- * If we have to reload gs, we must take care to
- * preserve our gs base.
- */
- local_irq_disable();
- load_gs(gs_sel);
-#ifdef CONFIG_X86_64
- wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
-#endif
- local_irq_enable();
-
- reload_tss();
- }
/*
* Profile KVM exit RIPs:
*/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-03-11 13:55    [W:0.046 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site