From: Jing Liu <jing2.liu@intel.com>
To: x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
pbonzini@redhat.com
Cc: seanjc@google.com, jun.nakajima@intel.com, kevin.tian@intel.com,
jing2.liu@linux.intel.com, jing2.liu@intel.com,
guang.zeng@intel.com, wei.w.wang@intel.com, yang.zhong@intel.com
Subject: [PATCH v2 22/23] kvm: x86: Disable interception for IA32_XFD on demand
Date: Fri, 17 Dec 2021 07:30:02 -0800 [thread overview]
Message-ID: <20211217153003.1719189-23-jing2.liu@intel.com> (raw)
In-Reply-To: <20211217153003.1719189-1-jing2.liu@intel.com>
Always intercepting IA32_XFD causes non-negligible overhead when this
register is updated frequently in the guest.
Disable r/w emulation after intercepting the first WRMSR(IA32_XFD)
with a non-zero value.
Disable WRMSR emulation implies that IA32_XFD becomes out-of-sync
with the software states in fpstate and the per-cpu xfd cache. Call
fpu_sync_guest_vmexit_xfd_state() to bring them back in-sync, before
preemption is enabled.
p.s. We have confirmed that SDM is being revised to say that
when setting IA32_XFD[18] the AMX register state is not guaranteed
to be preserved. This clarification avoids adding mess for a creative
guest which sets IA32_XFD[18]=1 before saving active AMX state to
its own storage.
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
---
arch/x86/include/asm/kvm-x86-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/vmx/vmx.c | 10 ++++++++++
arch/x86/kvm/vmx/vmx.h | 2 +-
arch/x86/kvm/x86.c | 6 ++++++
5 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index cefe1d81e2e8..60c27f9990e9 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -30,6 +30,7 @@ KVM_X86_OP(update_exception_bitmap)
KVM_X86_OP(get_msr)
KVM_X86_OP(set_msr)
KVM_X86_OP(get_segment_base)
+KVM_X86_OP_NULL(set_xfd_passthrough)
KVM_X86_OP(get_segment)
KVM_X86_OP(get_cpl)
KVM_X86_OP(set_segment)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 860ed500580c..b513c12fa39e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -640,6 +640,7 @@ struct kvm_vcpu_arch {
u64 smi_count;
bool tpr_access_reporting;
bool xsaves_enabled;
+ bool xfd_out_of_sync;
u64 ia32_xss;
u64 microcode_version;
u64 arch_capabilities;
@@ -1329,6 +1330,7 @@ struct kvm_x86_ops {
void (*update_exception_bitmap)(struct kvm_vcpu *vcpu);
int (*get_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr);
int (*set_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr);
+ void (*set_xfd_passthrough)(struct kvm_vcpu *vcpu);
u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg);
void (*get_segment)(struct kvm_vcpu *vcpu,
struct kvm_segment *var, int seg);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 483075045253..97a823a3f23f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -162,6 +162,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = {
MSR_FS_BASE,
MSR_GS_BASE,
MSR_KERNEL_GS_BASE,
+ MSR_IA32_XFD,
#endif
MSR_IA32_SYSENTER_CS,
MSR_IA32_SYSENTER_ESP,
@@ -1929,6 +1930,14 @@ static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu)
return debugctl;
}
+#ifdef CONFIG_X86_64
+static void vmx_set_xfd_passthrough(struct kvm_vcpu *vcpu)
+{
+ vmx_disable_intercept_for_msr(vcpu, MSR_IA32_XFD, MSR_TYPE_RW);
+ vcpu->arch.xfd_out_of_sync = true;
+}
+#endif
+
/*
* Writes msr value into the appropriate "register".
* Returns 0 on success, non-0 otherwise.
@@ -7664,6 +7673,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
#ifdef CONFIG_X86_64
.set_hv_timer = vmx_set_hv_timer,
.cancel_hv_timer = vmx_cancel_hv_timer,
+ .set_xfd_passthrough = vmx_set_xfd_passthrough,
#endif
.setup_mce = vmx_setup_mce,
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 4df2ac24ffc1..bf9d3051cd6c 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -340,7 +340,7 @@ struct vcpu_vmx {
struct lbr_desc lbr_desc;
/* Save desired MSR intercept (read: pass-through) state */
-#define MAX_POSSIBLE_PASSTHROUGH_MSRS 13
+#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14
struct {
DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 796a9f2d1f23..13ba1e066b55 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3686,6 +3686,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
fpu_update_guest_xfd(&vcpu->arch.guest_fpu, data);
+
+ if (data && kvm_x86_ops.set_xfd_passthrough)
+ static_call(kvm_x86_set_xfd_passthrough)(vcpu);
break;
case MSR_IA32_XFD_ERR:
if (!msr_info->host_initiated &&
@@ -10023,6 +10026,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (vcpu->arch.guest_fpu.xfd_err)
wrmsrl(MSR_IA32_XFD_ERR, 0);
+ if (vcpu->arch.xfd_out_of_sync)
+ fpu_sync_guest_vmexit_xfd_state();
+
/*
* Consume any pending interrupts, including the possible source of
* VM-Exit on SVM and any ticks that occur between VM-Exit and now.
--
2.27.0
next prev parent reply other threads:[~2021-12-17 15:30 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 15:29 [PATCH v2 00/23] AMX Support in KVM Jing Liu
2021-12-17 15:29 ` [PATCH v2 01/23] x86/fpu: Extend fpu_xstate_prctl() with guest permissions Jing Liu
2021-12-17 18:45 ` Thomas Gleixner
2021-12-17 18:47 ` Thomas Gleixner
2021-12-17 15:29 ` [PATCH v2 02/23] x86/fpu: Prepare guest FPU for dynamically enabled FPU features Jing Liu
2021-12-17 15:29 ` [PATCH v2 03/23] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Jing Liu
2021-12-17 15:29 ` [PATCH v2 04/23] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Jing Liu
2021-12-20 13:20 ` Paolo Bonzini
2021-12-17 15:29 ` [PATCH v2 05/23] kvm: x86: Check permitted dynamic xfeatures at KVM_SET_CPUID2 Jing Liu
2021-12-17 15:29 ` [PATCH v2 06/23] x86/fpu: Make XFD initialization in __fpstate_reset() a function argument Jing Liu
2021-12-17 15:29 ` [PATCH v2 07/23] x86/fpu: Add guest support to xfd_enable_feature() Jing Liu
2021-12-17 15:29 ` [PATCH v2 08/23] x86/fpu: Provide fpu_update_guest_perm_features() for guest Jing Liu
2021-12-17 18:50 ` Thomas Gleixner
2021-12-17 15:29 ` [PATCH v2 09/23] kvm: x86: Enable dynamic XSAVE features at KVM_SET_CPUID2 Jing Liu
2021-12-17 15:29 ` [PATCH v2 10/23] x86/fpu: Provide fpu_update_guest_xfd() for IA32_XFD emulation Jing Liu
2021-12-17 15:29 ` [PATCH v2 11/23] kvm: x86: Add emulation for IA32_XFD Jing Liu
2021-12-17 15:29 ` [PATCH v2 12/23] x86/fpu: Prepare xfd_err in struct fpu_guest Jing Liu
2021-12-17 15:29 ` [PATCH v2 13/23] kvm: x86: Intercept #NM for saving IA32_XFD_ERR Jing Liu
2021-12-17 15:29 ` [PATCH v2 14/23] kvm: x86: Emulate IA32_XFD_ERR for guest Jing Liu
2021-12-17 15:29 ` [PATCH v2 15/23] kvm: x86: Add XCR0 support for Intel AMX Jing Liu
2021-12-17 15:29 ` [PATCH v2 16/23] kvm: x86: Add CPUID " Jing Liu
2021-12-17 15:29 ` [PATCH v2 17/23] x86/fpu: add uabi_size to guest_fpu Jing Liu
2021-12-17 15:29 ` [PATCH v2 18/23] kvm: x86: Get/set expanded xstate buffer Jing Liu
2021-12-20 9:04 ` Paolo Bonzini
2021-12-21 2:45 ` Wang, Wei W
2021-12-21 8:45 ` Paolo Bonzini
2021-12-21 9:06 ` Wang, Wei W
2021-12-21 9:30 ` Paolo Bonzini
2021-12-17 15:29 ` [PATCH v2 19/23] kvm: selftests: Add support for KVM_CAP_XSAVE2 Jing Liu
2021-12-20 13:19 ` Paolo Bonzini
2021-12-17 15:30 ` [PATCH v2 20/23] docs: kvm: Add KVM_GET_XSAVE2 Jing Liu
2021-12-20 9:04 ` Paolo Bonzini
2021-12-17 15:30 ` [PATCH v2 21/23] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Jing Liu
2021-12-17 15:30 ` Jing Liu [this message]
2021-12-20 9:07 ` [PATCH v2 22/23] kvm: x86: Disable interception for IA32_XFD on demand Paolo Bonzini
2021-12-21 6:42 ` Liu, Jing2
2021-12-21 8:46 ` Paolo Bonzini
2021-12-17 15:30 ` [PATCH v2 23/23] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR Jing Liu
2021-12-20 9:08 ` Paolo Bonzini
2021-12-21 6:29 ` Liu, Jing2
2021-12-21 8:48 ` Paolo Bonzini
2021-12-21 9:00 ` Liu, Jing2
2021-12-21 9:05 ` Paolo Bonzini
2021-12-17 18:52 ` [PATCH v2 00/23] AMX Support in KVM Thomas Gleixner
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