Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 61d2ef2c authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: VMX: Add facility to atomically switch MSRs on guest entry/exit 



Some guest msr values cannot be used on the host (for example. EFER.NX=0),
so we need to switch them atomically during guest entry or exit.

Add a facility to program the vmx msr autoload registers accordingly.

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 5dfa3d17

arch/x86/kvm/vmx.c

+49 −0
Original line number Diff line number Diff line
@@ -98,6 +98,8 @@ module_param(ple_gap, int, S_IRUGO); 
static int ple_window = KVM_VMX_DEFAULT_PLE_WINDOW;

module_param(ple_window, int, S_IRUGO);



#define NR_AUTOLOAD_MSRS 1



struct vmcs {

	u32 revision_id;

	u32 abort;
@@ -125,6 +127,11 @@ struct vcpu_vmx { 
	u64 		      msr_guest_kernel_gs_base;

#endif

	struct vmcs          *vmcs;

	struct msr_autoload {

		unsigned nr;

		struct vmx_msr_entry guest[NR_AUTOLOAD_MSRS];

		struct vmx_msr_entry host[NR_AUTOLOAD_MSRS];

	} msr_autoload;

	struct {

		int           loaded;

		u16           fs_sel, gs_sel, ldt_sel;
@@ -595,6 +602,46 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) 
	vmcs_write32(EXCEPTION_BITMAP, eb);

}



static void clear_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr)

{

	unsigned i;

	struct msr_autoload *m = &vmx->msr_autoload;



	for (i = 0; i < m->nr; ++i)

		if (m->guest[i].index == msr)

			break;



	if (i == m->nr)

		return;

	--m->nr;

	m->guest[i] = m->guest[m->nr];

	m->host[i] = m->host[m->nr];

	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, m->nr);

	vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, m->nr);

}



static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,

				  u64 guest_val, u64 host_val)

{

	unsigned i;

	struct msr_autoload *m = &vmx->msr_autoload;



	for (i = 0; i < m->nr; ++i)

		if (m->guest[i].index == msr)

			break;



	if (i == m->nr) {

		++m->nr;

		vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, m->nr);

		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, m->nr);

	}



	m->guest[i].index = msr;

	m->guest[i].value = guest_val;

	m->host[i].index = msr;

	m->host[i].value = host_val;

}



static void reload_tss(void)

{

	/*
@@ -2470,7 +2517,9 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx) 
	vmcs_writel(HOST_RIP, kvm_vmx_return); /* 22.2.5 */

	vmcs_write32(VM_EXIT_MSR_STORE_COUNT, 0);

	vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, 0);

	vmcs_write64(VM_EXIT_MSR_LOAD_ADDR, __pa(vmx->msr_autoload.host));

	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, 0);

	vmcs_write64(VM_ENTRY_MSR_LOAD_ADDR, __pa(vmx->msr_autoload.guest));



	rdmsr(MSR_IA32_SYSENTER_CS, host_sysenter_cs, junk);

	vmcs_write32(HOST_IA32_SYSENTER_CS, host_sysenter_cs);