Ingo Molnar wrote:
Subject: [patch] KVM: always reload segment selectors
From: Ingo Molnar <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>
---
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);
btw, looking at the code, we could just remove fs from the
fs_gs_reload_needed and make in unconditional. VT knows how to reload
segments, except if they're user segments (groan). In the case of fs,
if it's used for the pda, it's obviously a kernel segment.
gs is different: since only the segment base is loaded (via swapgs), the
selector part could well be a userspace selector, and thus the
irq-protected reload is needed.
Anyway, I'm applying the patch as the above discourse is irrelevant to
the fix.
--
error compiling committee.c: too many arguments to function
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