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Subject[133/139] KVM: VMX: Save/restore rflags.vm correctly in real mode
2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Avi Kivity <avi@redhat.com>

(Cherry-picked from commit 78ac8b47c566dd6177a3b9b291b756ccb70670b7)

Currently we set eflags.vm unconditionally when entering real mode emulation
through virtual-8086 mode, and clear it unconditionally when we enter protected
mode. The means that the following sequence

KVM_SET_REGS (rflags.vm=1)
KVM_SET_SREGS (cr0.pe=1)

Ends up with rflags.vm clear due to KVM_SET_SREGS triggering enter_pmode().

Fix by shadowing rflags.vm (and rflags.iopl) correctly while in real mode:
reads and writes to those bits access a shadow register instead of the actual
register.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/kvm/vmx.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -61,6 +61,8 @@ module_param_named(unrestricted_guest,
static int __read_mostly emulate_invalid_guest_state = 0;
module_param(emulate_invalid_guest_state, bool, S_IRUGO);

+#define RMODE_GUEST_OWNED_EFLAGS_BITS (~(X86_EFLAGS_IOPL | X86_EFLAGS_VM))
+
/*
* These 2 parameters are used to config the controls for Pause-Loop Exiting:
* ple_gap: upper bound on the amount of time between two successive
@@ -115,7 +117,7 @@ struct vcpu_vmx {
} host_state;
struct {
int vm86_active;
- u8 save_iopl;
+ ulong save_rflags;
struct kvm_save_segment {
u16 selector;
unsigned long base;
@@ -787,18 +789,23 @@ static void vmx_fpu_deactivate(struct kv

static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
{
- unsigned long rflags;
+ unsigned long rflags, save_rflags;

rflags = vmcs_readl(GUEST_RFLAGS);
- if (to_vmx(vcpu)->rmode.vm86_active)
- rflags &= ~(unsigned long)(X86_EFLAGS_IOPL | X86_EFLAGS_VM);
+ if (to_vmx(vcpu)->rmode.vm86_active) {
+ rflags &= RMODE_GUEST_OWNED_EFLAGS_BITS;
+ save_rflags = to_vmx(vcpu)->rmode.save_rflags;
+ rflags |= save_rflags & ~RMODE_GUEST_OWNED_EFLAGS_BITS;
+ }
return rflags;
}

static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
{
- if (to_vmx(vcpu)->rmode.vm86_active)
+ if (to_vmx(vcpu)->rmode.vm86_active) {
+ to_vmx(vcpu)->rmode.save_rflags = rflags;
rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;
+ }
vmcs_writel(GUEST_RFLAGS, rflags);
}

@@ -1431,8 +1438,8 @@ static void enter_pmode(struct kvm_vcpu
vmcs_write32(GUEST_TR_AR_BYTES, vmx->rmode.tr.ar);

flags = vmcs_readl(GUEST_RFLAGS);
- flags &= ~(X86_EFLAGS_IOPL | X86_EFLAGS_VM);
- flags |= (vmx->rmode.save_iopl << IOPL_SHIFT);
+ flags &= RMODE_GUEST_OWNED_EFLAGS_BITS;
+ flags |= vmx->rmode.save_rflags & ~RMODE_GUEST_OWNED_EFLAGS_BITS;
vmcs_writel(GUEST_RFLAGS, flags);

vmcs_writel(GUEST_CR4, (vmcs_readl(GUEST_CR4) & ~X86_CR4_VME) |
@@ -1501,8 +1508,7 @@ static void enter_rmode(struct kvm_vcpu
vmcs_write32(GUEST_TR_AR_BYTES, 0x008b);

flags = vmcs_readl(GUEST_RFLAGS);
- vmx->rmode.save_iopl
- = (flags & X86_EFLAGS_IOPL) >> IOPL_SHIFT;
+ vmx->rmode.save_rflags = flags;

flags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;




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