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Commit 78ac8b47 authored by Avi Kivity's avatar Avi Kivity
Browse files

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



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: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 114be429

arch/x86/kvm/vmx.c

+15 −9
Original line number Diff line number Diff line
@@ -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;