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KVM: VMX: Save/restore rflags.vm correctly in real mode

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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>
This commit is contained in:
Avi Kivity 2010-04-08 18:19:35 +03:00
parent 114be429c8
commit 78ac8b47c5
1 changed files with 15 additions and 9 deletions
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24
arch/x86/kvm/vmx.c
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@ -77,6 +77,8 @@ module_param(emulate_invalid_guest_state, bool, S_IRUGO);
#define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
#define KVM_RMODE_VM_CR4_ALWAYS_ON (X86_CR4_VME | X86_CR4_PAE | X86_CR4_VMXE)
#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
@ -131,7 +133,7 @@ struct vcpu_vmx {
} host_state;
struct {
int vm86_active;
u8 save_iopl;
ulong save_rflags;
struct kvm_save_segment {
u16 selector;
unsigned long base;
@ -818,18 +820,23 @@ static void vmx_fpu_deactivate(struct kvm_vcpu *vcpu)
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);
}
@ -1483,8 +1490,8 @@ static void enter_pmode(struct kvm_vcpu *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) |
@ -1557,8 +1564,7 @@ static void enter_rmode(struct kvm_vcpu *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;