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

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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: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity 2010-04-28 16:40:38 +03:00
parent 5dfa3d170e
commit 61d2ef2ce3
1 changed files with 49 additions and 0 deletions
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49
arch/x86/kvm/vmx.c
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@ -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);