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Subject[PATCH 3.16 093/305] KVM: x86: remove code for lazy FPU handling
3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@redhat.com>

commit bd7e5b0899a429445cc6e3037c13f8b5ae3be903 upstream.

The FPU is always active now when running KVM.

Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 3.16:
- eagerfpu is still optional (but enabled by default) so disable KVM if
eagerfpu is disabled
- Remove one additional use of KVM_REQ_DEACTIVATE_FPU which was
removed earlier upstream in commit c592b5734706
"x86/fpu: Remove use_eager_fpu()"
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -711,8 +711,6 @@ struct kvm_x86_ops {
void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
- void (*fpu_activate)(struct kvm_vcpu *vcpu);
- void (*fpu_deactivate)(struct kvm_vcpu *vcpu);

void (*tlb_flush)(struct kvm_vcpu *vcpu);

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1119,7 +1119,6 @@ static void init_vmcb(struct vcpu_svm *s
struct vmcb_control_area *control = &svm->vmcb->control;
struct vmcb_save_area *save = &svm->vmcb->save;

- svm->vcpu.fpu_active = 1;
svm->vcpu.arch.hflags = 0;

set_cr_intercept(svm, INTERCEPT_CR0_READ);
@@ -1574,15 +1573,12 @@ static void update_cr0_intercept(struct
ulong gcr0 = svm->vcpu.arch.cr0;
u64 *hcr0 = &svm->vmcb->save.cr0;

- if (!svm->vcpu.fpu_active)
- *hcr0 |= SVM_CR0_SELECTIVE_MASK;
- else
- *hcr0 = (*hcr0 & ~SVM_CR0_SELECTIVE_MASK)
- | (gcr0 & SVM_CR0_SELECTIVE_MASK);
+ *hcr0 = (*hcr0 & ~SVM_CR0_SELECTIVE_MASK)
+ | (gcr0 & SVM_CR0_SELECTIVE_MASK);

mark_dirty(svm->vmcb, VMCB_CR);

- if (gcr0 == *hcr0 && svm->vcpu.fpu_active) {
+ if (gcr0 == *hcr0) {
clr_cr_intercept(svm, INTERCEPT_CR0_READ);
clr_cr_intercept(svm, INTERCEPT_CR0_WRITE);
} else {
@@ -1613,8 +1609,6 @@ static void svm_set_cr0(struct kvm_vcpu
if (!npt_enabled)
cr0 |= X86_CR0_PG | X86_CR0_WP;

- if (!vcpu->fpu_active)
- cr0 |= X86_CR0_TS;
/*
* re-enable caching here because the QEMU bios
* does not do it - this results in some delay at
@@ -1834,22 +1828,6 @@ static int ac_interception(struct vcpu_s
return 1;
}

-static void svm_fpu_activate(struct kvm_vcpu *vcpu)
-{
- struct vcpu_svm *svm = to_svm(vcpu);
-
- clr_exception_intercept(svm, NM_VECTOR);
-
- svm->vcpu.fpu_active = 1;
- update_cr0_intercept(svm);
-}
-
-static int nm_interception(struct vcpu_svm *svm)
-{
- svm_fpu_activate(&svm->vcpu);
- return 1;
-}
-
static bool is_erratum_383(void)
{
int err, i;
@@ -2227,9 +2205,6 @@ static int nested_svm_exit_special(struc
if (!npt_enabled && svm->apf_reason == 0)
return NESTED_EXIT_HOST;
break;
- case SVM_EXIT_EXCP_BASE + NM_VECTOR:
- nm_interception(svm);
- break;
default:
break;
}
@@ -3448,7 +3423,6 @@ static int (*const svm_exit_handlers[])(
[SVM_EXIT_EXCP_BASE + BP_VECTOR] = bp_interception,
[SVM_EXIT_EXCP_BASE + UD_VECTOR] = ud_interception,
[SVM_EXIT_EXCP_BASE + PF_VECTOR] = pf_interception,
- [SVM_EXIT_EXCP_BASE + NM_VECTOR] = nm_interception,
[SVM_EXIT_EXCP_BASE + MC_VECTOR] = mc_interception,
[SVM_EXIT_EXCP_BASE + AC_VECTOR] = ac_interception,
[SVM_EXIT_INTR] = intr_interception,
@@ -4285,14 +4259,6 @@ static bool svm_has_wbinvd_exit(void)
return true;
}

-static void svm_fpu_deactivate(struct kvm_vcpu *vcpu)
-{
- struct vcpu_svm *svm = to_svm(vcpu);
-
- set_exception_intercept(svm, NM_VECTOR);
- update_cr0_intercept(svm);
-}
-
#define PRE_EX(exit) { .exit_code = (exit), \
.stage = X86_ICPT_PRE_EXCEPT, }
#define POST_EX(exit) { .exit_code = (exit), \
@@ -4526,8 +4492,6 @@ static struct kvm_x86_ops svm_x86_ops =
.cache_reg = svm_cache_reg,
.get_rflags = svm_get_rflags,
.set_rflags = svm_set_rflags,
- .fpu_activate = svm_fpu_activate,
- .fpu_deactivate = svm_fpu_deactivate,

.tlb_flush = svm_flush_tlb,

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1491,7 +1491,7 @@ static void update_exception_bitmap(stru
u32 eb;

eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
- (1u << NM_VECTOR) | (1u << DB_VECTOR) | (1u << AC_VECTOR);
+ (1u << DB_VECTOR) | (1u << AC_VECTOR);
if ((vcpu->guest_debug &
(KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) ==
(KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP))
@@ -1500,8 +1500,6 @@ static void update_exception_bitmap(stru
eb = ~0;
if (enable_ept)
eb &= ~(1u << PF_VECTOR); /* bypass_guest_pf = 0 */
- if (vcpu->fpu_active)
- eb &= ~(1u << NM_VECTOR);

/* When we are running a nested L2 guest and L1 specified for it a
* certain exception bitmap, we must trap the same exceptions and pass
@@ -1904,25 +1902,6 @@ static void vmx_vcpu_put(struct kvm_vcpu
}
}

-static void vmx_fpu_activate(struct kvm_vcpu *vcpu)
-{
- ulong cr0;
-
- if (vcpu->fpu_active)
- return;
- vcpu->fpu_active = 1;
- cr0 = vmcs_readl(GUEST_CR0);
- cr0 &= ~(X86_CR0_TS | X86_CR0_MP);
- cr0 |= kvm_read_cr0_bits(vcpu, X86_CR0_TS | X86_CR0_MP);
- vmcs_writel(GUEST_CR0, cr0);
- update_exception_bitmap(vcpu);
- vcpu->arch.cr0_guest_owned_bits = X86_CR0_TS;
- if (is_guest_mode(vcpu))
- vcpu->arch.cr0_guest_owned_bits &=
- ~get_vmcs12(vcpu)->cr0_guest_host_mask;
- vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
-}
-
static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu);

/*
@@ -1941,33 +1920,6 @@ static inline unsigned long nested_read_
(fields->cr4_read_shadow & fields->cr4_guest_host_mask);
}

-static void vmx_fpu_deactivate(struct kvm_vcpu *vcpu)
-{
- /* Note that there is no vcpu->fpu_active = 0 here. The caller must
- * set this *before* calling this function.
- */
- vmx_decache_cr0_guest_bits(vcpu);
- vmcs_set_bits(GUEST_CR0, X86_CR0_TS | X86_CR0_MP);
- update_exception_bitmap(vcpu);
- vcpu->arch.cr0_guest_owned_bits = 0;
- vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
- if (is_guest_mode(vcpu)) {
- /*
- * L1's specified read shadow might not contain the TS bit,
- * so now that we turned on shadowing of this bit, we need to
- * set this bit of the shadow. Like in nested_vmx_run we need
- * nested_read_cr0(vmcs12), but vmcs12->guest_cr0 is not yet
- * up-to-date here because we just decached cr0.TS (and we'll
- * only update vmcs12->guest_cr0 on nested exit).
- */
- struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
- vmcs12->guest_cr0 = (vmcs12->guest_cr0 & ~X86_CR0_TS) |
- (vcpu->arch.cr0 & X86_CR0_TS);
- vmcs_writel(CR0_READ_SHADOW, nested_read_cr0(vmcs12));
- } else
- vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0);
-}
-
static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
{
unsigned long rflags, save_rflags;
@@ -3586,9 +3538,6 @@ static void vmx_set_cr0(struct kvm_vcpu
if (enable_ept)
ept_update_paging_mode_cr0(&hw_cr0, cr0, vcpu);

- if (!vcpu->fpu_active)
- hw_cr0 |= X86_CR0_TS | X86_CR0_MP;
-
vmcs_writel(CR0_READ_SHADOW, cr0);
vmcs_writel(GUEST_CR0, hw_cr0);
vcpu->arch.cr0 = cr0;
@@ -4644,7 +4593,9 @@ static int vmx_vcpu_setup(struct vcpu_vm
/* 22.2.1, 20.8.1 */
vm_entry_controls_init(vmx, vmcs_config.vmentry_ctrl);

- vmcs_writel(CR0_GUEST_HOST_MASK, ~0UL);
+ vmx->vcpu.arch.cr0_guest_owned_bits = X86_CR0_TS;
+ vmcs_writel(CR0_GUEST_HOST_MASK, ~X86_CR0_TS);
+
set_cr4_guest_host_mask(vmx);

return 0;
@@ -4736,7 +4687,7 @@ static void vmx_vcpu_reset(struct kvm_vc
vmx_set_cr0(&vmx->vcpu, kvm_read_cr0(vcpu)); /* enter rmode */
vmx_set_cr4(&vmx->vcpu, 0);
vmx_set_efer(&vmx->vcpu, 0);
- vmx_fpu_activate(&vmx->vcpu);
+
update_exception_bitmap(&vmx->vcpu);

vpid_sync_context(vmx);
@@ -5022,11 +4973,6 @@ static int handle_exception(struct kvm_v
if (is_nmi(intr_info))
return 1; /* already handled by vmx_vcpu_run() */

- if (is_no_device(intr_info)) {
- vmx_fpu_activate(vcpu);
- return 1;
- }
-
if (is_invalid_opcode(intr_info)) {
er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD);
if (er == EMULATE_USER_EXIT)
@@ -5218,22 +5164,6 @@ static int handle_set_cr4(struct kvm_vcp
return kvm_set_cr4(vcpu, val);
}

-/* called to set cr0 as approriate for clts instruction exit. */
-static void handle_clts(struct kvm_vcpu *vcpu)
-{
- if (is_guest_mode(vcpu)) {
- /*
- * We get here when L2 did CLTS, and L1 didn't shadow CR0.TS
- * but we did (!fpu_active). We need to keep GUEST_CR0.TS on,
- * just pretend it's off (also in arch.cr0 for fpu_activate).
- */
- vmcs_writel(CR0_READ_SHADOW,
- vmcs_readl(CR0_READ_SHADOW) & ~X86_CR0_TS);
- vcpu->arch.cr0 &= ~X86_CR0_TS;
- } else
- vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
-}
-
static int handle_cr(struct kvm_vcpu *vcpu)
{
unsigned long exit_qualification, val;
@@ -5276,10 +5206,10 @@ static int handle_cr(struct kvm_vcpu *vc
}
break;
case 2: /* clts */
- handle_clts(vcpu);
+ WARN_ONCE(1, "Guest should always own CR0.TS");
+ vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
trace_kvm_cr_write(0, kvm_read_cr0(vcpu));
skip_emulated_instruction(vcpu);
- vmx_fpu_activate(vcpu);
return 1;
case 1: /*mov from cr*/
switch (cr) {
@@ -8299,8 +8229,8 @@ static void prepare_vmcs02(struct kvm_vc
vmx_set_efer(vcpu, vcpu->arch.efer);

/*
- * This sets GUEST_CR0 to vmcs12->guest_cr0, with possibly a modified
- * TS bit (for lazy fpu) and bits which we consider mandatory enabled.
+ * This sets GUEST_CR0 to vmcs12->guest_cr0, possibly modifying those
+ * bits which we consider mandatory enabled.
* The CR0_READ_SHADOW is what L2 should have expected to read given
* the specifications by L1; It's not enough to take
* vmcs12->cr0_read_shadow because on our cr0_guest_host_mask we we
@@ -8814,24 +8744,15 @@ static void load_vmcs12_host_state(struc
vmx_set_rflags(vcpu, X86_EFLAGS_FIXED);
/*
* Note that calling vmx_set_cr0 is important, even if cr0 hasn't
- * actually changed, because it depends on the current state of
- * fpu_active (which may have changed).
- * Note that vmx_set_cr0 refers to efer set above.
+ * actually changed, because vmx_set_cr0 refers to efer set above.
+ *
+ * CR0_GUEST_HOST_MASK is already set in the original vmcs01
+ * (KVM doesn't change it);
*/
+ vcpu->arch.cr0_guest_owned_bits = X86_CR0_TS;
vmx_set_cr0(vcpu, vmcs12->host_cr0);
- /*
- * If we did fpu_activate()/fpu_deactivate() during L2's run, we need
- * to apply the same changes to L1's vmcs. We just set cr0 correctly,
- * but we also need to update cr0_guest_host_mask and exception_bitmap.
- */
- update_exception_bitmap(vcpu);
- vcpu->arch.cr0_guest_owned_bits = (vcpu->fpu_active ? X86_CR0_TS : 0);
- vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);

- /*
- * Note that CR4_GUEST_HOST_MASK is already set in the original vmcs01
- * (KVM doesn't change it)- no reason to call set_cr4_guest_host_mask();
- */
+ /* Same as above - no reason to call set_cr4_guest_host_mask(). */
vcpu->arch.cr4_guest_owned_bits = ~vmcs_readl(CR4_GUEST_HOST_MASK);
vmx_set_cr4(vcpu, vmcs12->host_cr4);

@@ -9081,8 +9002,6 @@ static struct kvm_x86_ops vmx_x86_ops =
.cache_reg = vmx_cache_reg,
.get_rflags = vmx_get_rflags,
.set_rflags = vmx_set_rflags,
- .fpu_activate = vmx_fpu_activate,
- .fpu_deactivate = vmx_fpu_deactivate,

.tlb_flush = vmx_flush_tlb,

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5698,6 +5698,12 @@ int kvm_arch_init(void *opaque)
goto out;
}

+ if (!boot_cpu_has(X86_FEATURE_EAGER_FPU)) {
+ pr_err("kvm: requires eagerfpu\n");
+ r = -EOPNOTSUPP;
+ goto out;
+ }
+
if (!ops->cpu_has_kvm_support()) {
printk(KERN_ERR "kvm: no hardware support\n");
r = -EOPNOTSUPP;
@@ -6099,10 +6105,6 @@ static int vcpu_enter_guest(struct kvm_v
r = 0;
goto out;
}
- if (kvm_check_request(KVM_REQ_DEACTIVATE_FPU, vcpu)) {
- vcpu->fpu_active = 0;
- kvm_x86_ops->fpu_deactivate(vcpu);
- }
if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
/* Page is swapped out. Do synthetic halt */
vcpu->arch.apf.halted = true;
@@ -6159,8 +6161,7 @@ static int vcpu_enter_guest(struct kvm_v
preempt_disable();

kvm_x86_ops->prepare_guest_switch(vcpu);
- if (vcpu->fpu_active)
- kvm_load_guest_fpu(vcpu);
+ kvm_load_guest_fpu(vcpu);
vcpu->mode = IN_GUEST_MODE;

srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
@@ -6917,7 +6918,6 @@ void kvm_put_guest_fpu(struct kvm_vcpu *
fpu_save_init(&vcpu->arch.guest_fpu);
__kernel_fpu_end();
++vcpu->stat.fpu_reload;
- kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
trace_kvm_fpu(0);
}

--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -121,7 +121,6 @@ static inline bool is_error_page(struct
#define KVM_REQ_MMU_SYNC 7
#define KVM_REQ_CLOCK_UPDATE 8
#define KVM_REQ_KICK 9
-#define KVM_REQ_DEACTIVATE_FPU 10
#define KVM_REQ_EVENT 11
#define KVM_REQ_APF_HALT 12
#define KVM_REQ_STEAL_UPDATE 13
@@ -232,7 +231,6 @@ struct kvm_vcpu {
struct mutex mutex;
struct kvm_run *run;

- int fpu_active;
int guest_fpu_loaded, guest_xcr0_loaded;
wait_queue_head_t wq;
struct pid *pid;
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