diff options
| author | Suresh Siddha <suresh.b.siddha@intel.com> | 2012-09-20 11:01:49 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2012-09-21 16:59:04 -0700 |
| commit | b1a74bf8212367be2b1d6685c11a84e056eaaaf1 (patch) | |
| tree | 598eafb9d082cd7ba4d6299dc63bd3511963186d /arch/x86/kvm | |
| parent | a8615af4bc3621cb01096541dafa6f68352ec2d9 (diff) | |
x86, kvm: fix kvm's usage of kernel_fpu_begin/end()
Preemption is disabled between kernel_fpu_begin/end() and as such
it is not a good idea to use these routines in kvm_load/put_guest_fpu()
which can be very far apart.
kvm_load/put_guest_fpu() routines are already called with
preemption disabled and KVM already uses the preempt notifier to save
the guest fpu state using kvm_put_guest_fpu().
So introduce __kernel_fpu_begin/end() routines which don't touch
preemption and use them instead of kernel_fpu_begin/end()
for KVM's use model of saving/restoring guest FPU state.
Also with this change (and with eagerFPU model), fix the host cr0.TS vm-exit
state in the case of VMX. For eagerFPU case, host cr0.TS is always clear.
So no need to worry about it. For the traditional lazyFPU restore case,
change the cr0.TS bit for the host state during vm-exit to be always clear
and cr0.TS bit is set in the __vmx_load_host_state() when the FPU
(guest FPU or the host task's FPU) state is not active. This ensures
that the host/guest FPU state is properly saved, restored
during context-switch and with interrupts (using irq_fpu_usable()) not
stomping on the active FPU state.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1348164109.26695.338.camel@sbsiddha-desk.sc.intel.com
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/vmx.c | 10 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 4 |
2 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index c00f03de1b79..70dfcec3c463 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1493,8 +1493,12 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx) #ifdef CONFIG_X86_64 wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); #endif - if (user_has_fpu()) - clts(); + /* + * If the FPU is not active (through the host task or + * the guest vcpu), then restore the cr0.TS bit. + */ + if (!user_has_fpu() && !vmx->vcpu.guest_fpu_loaded) + stts(); load_gdt(&__get_cpu_var(host_gdt)); } @@ -3730,7 +3734,7 @@ static void vmx_set_constant_host_state(void) unsigned long tmpl; struct desc_ptr dt; - vmcs_writel(HOST_CR0, read_cr0() | X86_CR0_TS); /* 22.2.3 */ + vmcs_writel(HOST_CR0, read_cr0() & ~X86_CR0_TS); /* 22.2.3 */ vmcs_writel(HOST_CR4, read_cr4()); /* 22.2.3, 22.2.5 */ vmcs_writel(HOST_CR3, read_cr3()); /* 22.2.3 FIXME: shadow tables */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index cf637f572bdd..02b2cd520693 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5972,7 +5972,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) */ kvm_put_guest_xcr0(vcpu); vcpu->guest_fpu_loaded = 1; - kernel_fpu_begin(); + __kernel_fpu_begin(); fpu_restore_checking(&vcpu->arch.guest_fpu); trace_kvm_fpu(1); } @@ -5986,7 +5986,7 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) vcpu->guest_fpu_loaded = 0; fpu_save_init(&vcpu->arch.guest_fpu); - kernel_fpu_end(); + __kernel_fpu_end(); ++vcpu->stat.fpu_reload; kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu); trace_kvm_fpu(0); |