During initialization, WinXP.32 switches to virtual-8086 mode, with
paging enabled, to use VGABIOS functions.
Since enter_pmode unconditionally clears IOPL and VM bits in RFLAGS
flags = vmcs_readl(GUEST_RFLAGS);
flags &= ~(X86_EFLAGS_IOPL | X86_EFLAGS_VM);
flags |= (vmx->rmode.save_iopl << IOPL_SHIFT);
vmcs_writel(GUEST_RFLAGS, flags);
And the order of loading state is set_regs (rflags) followed by
set_sregs (cr0), these bits are lost across save/restore:
savevm 1
kvm_arch_save_regs EIP=7a04 cr0=8001003b eflags=33286
system_reset
loadvm 1
kvm_arch_save_regs EIP=7a04 cr0=8001003b eflags=10286
cont
kvm: unhandled exit 80000021
kvm_run returned -22
The following patch fixes it, but it has some drawbacks:
- cpu_synchronize_state+writeback is noticeably slow with tpr patching,
this makes it slower.
- Should be conditional on VMX !unrestricted guest.
- Its a fugly workaround.
Any better ideas?
diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index 748ff69..9821653 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -956,6 +956,7 @@ void kvm_arch_load_regs(CPUState *env, int level)
sregs.efer = env->efer;
kvm_set_sregs(env, &sregs);
+ kvm_set_regs(env, ®s);
/* msrs */
n = 0;
--
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