On 08/18/2014 01:51 PM, Paolo Bonzini wrote:
Il 18/08/2014 12:26, Avi Kivity ha scritto:
On 08/18/2014 01:20 PM, Paolo Bonzini wrote:
Il 18/08/2014 11:50, Wanpeng Li ha scritto:
fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on
clts), however, there is no user currently, this patch drop it.
Reviewed-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 -
arch/x86/kvm/svm.c | 1 -
arch/x86/kvm/vmx.c | 1 -
3 files changed, 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h
b/arch/x86/include/asm/kvm_host.h
index 5724601..b68f3e5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -710,7 +710,6 @@ 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);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ddf7427..1f49c86 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4349,7 +4349,6 @@ 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,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 71cbee5..2963303 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8896,7 +8896,6 @@ 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,
Avi/Gleb, do you remember any particular reason for this?
IIRC (vaguely) if we expect the fpu to be used in the near future, we
activate it eagerly so that we don't fault when it is used.
Prevents the sequence:
guest user: use fpu
#NM
host: reflect #NM to guest
guest kernel: CLTS
guest kernel: switch fpu state
#NM
host: switch fpu
guest kernel: switch fpu state (restarted)
guest user: use fpu (restarted)
Why was the user removed? Full-time eager fpu?
No, I mean any reason to keep the hooks.
If there are no callers, I can't think of any.
In the meanwhile I found it myself:
commit 2d04a05bd7e93c13f13a82ac40de4065a99d069b
Author: Avi Kivity <avi@xxxxxxxxxx>
Date: Wed Apr 20 15:32:49 2011 +0300
KVM: x86 emulator: emulate CLTS internally
Avoid using ctxt->vcpu; we can do everything with ->get_cr() and ->set_cr().
A side effect is that we no longer activate the fpu on emulated CLTS; but that
should be very rare.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
vmx_fpu_activate and svm_fpu_activate are still called on #NM and CLTS, but
never from common code after the above patch.
Activation on CLTS is currently VMX only; I guess on AMD we could check the
decode assists' CR_VALID bit and instruction length to detect CLTS.
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