RE: [PATCH 2/2] Expose tsc deadline timer cpuid to guest

From: "Liu, Jinsong" <jinsong.liu@intel.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Alexey Zaytsev <alexey.zaytsev@gmail.com>,
	kvm <kvm@vger.kernel.org>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: RE: [PATCH 2/2] Expose tsc deadline timer cpuid to guest
Date: Tue, 28 Feb 2012 10:30:56 +0000	[thread overview]
Message-ID: <DE8DF0795D48FD4CA783C40EC82923350B8532@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <4F4BBAEC.2040603@siemens.com>

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> 
> My point is that
> 
>   qemu-version-A [-cpu whatever]
> 
> should provide the same VM as
> 
>   qemu-version-B -machine pc-A [-cpu whatever]
> 
> specifically if you leave out the cpu specification.
> 
> So the compat machine could establish a feature mask (e.g. append some
> "-tsc_deadline" in this case). But, indeed, we need a new channel for
> this. 
> 

Yes, if such requirement need to be satisfied, I agree we need a new channel to solve this kind of common issue.

As for tsc deadline timer feature exposing, I write an updated patch as attached.
1). It exposes tsc deadline timer feature to guest if in-kernel irqchip is used and kvm has emulated tsc deadline timer;
2). It also authorizes user to control the feature exposing via a cpu feature flag;

Thanks,
Jinsong

====================
>From 5b7d5f459b621686e78e437010ce34748bcb9e8e Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@intel.com>
Date: Wed, 29 Feb 2012 01:53:15 +0800
Subject: [PATCH] Expose tsc deadline timer feature to guest

It exposes tsc deadline timer feature to guest if in-kernel irqchip is used
and kvm has emulated tsc deadline timer.
It also authorizes user to control the feature exposing via a cpu feature flag.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
---
 target-i386/cpu.h   |    1 +
 target-i386/cpuid.c |    2 +-
 target-i386/kvm.c   |    4 ++++
 3 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index d92be5d..3409afe 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -399,6 +399,7 @@
 #define CPUID_EXT_X2APIC   (1 << 21)
 #define CPUID_EXT_MOVBE    (1 << 22)
 #define CPUID_EXT_POPCNT   (1 << 23)
+#define CPUID_EXT_TSC_DEADLINE_TIMER (1 << 24)
 #define CPUID_EXT_XSAVE    (1 << 26)
 #define CPUID_EXT_OSXSAVE  (1 << 27)
 #define CPUID_EXT_HYPERVISOR  (1 << 31)
diff --git a/target-i386/cpuid.c b/target-i386/cpuid.c
index b9bfeaf..ac4b79c 100644
--- a/target-i386/cpuid.c
+++ b/target-i386/cpuid.c
@@ -50,7 +50,7 @@ static const char *ext_feature_name[] = {
     "fma", "cx16", "xtpr", "pdcm",
     NULL, NULL, "dca", "sse4.1|sse4_1",
     "sse4.2|sse4_2", "x2apic", "movbe", "popcnt",
-    NULL, "aes", "xsave", "osxsave",
+    "tsc_deadline", "aes", "xsave", "osxsave",
     "avx", NULL, NULL, "hypervisor",
 };
 static const char *ext2_feature_name[] = {
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 7079e87..2639699 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -370,6 +370,10 @@ int kvm_arch_init_vcpu(CPUState *env)
     i = env->cpuid_ext_features & CPUID_EXT_HYPERVISOR;
     env->cpuid_ext_features &= kvm_arch_get_supported_cpuid(s, 1, 0, R_ECX);
     env->cpuid_ext_features |= i;
+    if (!kvm_irqchip_in_kernel() ||
+        !kvm_check_extension(s, KVM_CAP_TSC_DEADLINE_TIMER)) {
+        env->cpuid_ext_features &= ~CPUID_EXT_TSC_DEADLINE_TIMER;
+    }
 
     env->cpuid_ext2_features &= kvm_arch_get_supported_cpuid(s, 0x80000001,
                                                              0, R_EDX);
-- 
1.7.1

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From 5b7d5f459b621686e78e437010ce34748bcb9e8e Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@intel.com>
Date: Wed, 29 Feb 2012 01:53:15 +0800
Subject: [PATCH] Expose tsc deadline timer feature to guest

It exposes tsc deadline timer feature to guest if in-kernel irqchip is used
and kvm has emulated tsc deadline timer.
It also authorizes user to control the feature exposing via a cpu feature flag.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
---
 target-i386/cpu.h   |    1 +
 target-i386/cpuid.c |    2 +-
 target-i386/kvm.c   |    4 ++++
 3 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index d92be5d..3409afe 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -399,6 +399,7 @@
 #define CPUID_EXT_X2APIC   (1 << 21)
 #define CPUID_EXT_MOVBE    (1 << 22)
 #define CPUID_EXT_POPCNT   (1 << 23)
+#define CPUID_EXT_TSC_DEADLINE_TIMER (1 << 24)
 #define CPUID_EXT_XSAVE    (1 << 26)
 #define CPUID_EXT_OSXSAVE  (1 << 27)
 #define CPUID_EXT_HYPERVISOR  (1 << 31)
diff --git a/target-i386/cpuid.c b/target-i386/cpuid.c
index b9bfeaf..ac4b79c 100644
--- a/target-i386/cpuid.c
+++ b/target-i386/cpuid.c
@@ -50,7 +50,7 @@ static const char *ext_feature_name[] = {
     "fma", "cx16", "xtpr", "pdcm",
     NULL, NULL, "dca", "sse4.1|sse4_1",
     "sse4.2|sse4_2", "x2apic", "movbe", "popcnt",
-    NULL, "aes", "xsave", "osxsave",
+    "tsc_deadline", "aes", "xsave", "osxsave",
     "avx", NULL, NULL, "hypervisor",
 };
 static const char *ext2_feature_name[] = {
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 7079e87..2639699 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -370,6 +370,10 @@ int kvm_arch_init_vcpu(CPUState *env)
     i = env->cpuid_ext_features & CPUID_EXT_HYPERVISOR;
     env->cpuid_ext_features &= kvm_arch_get_supported_cpuid(s, 1, 0, R_ECX);
     env->cpuid_ext_features |= i;
+    if (!kvm_irqchip_in_kernel() ||
+        !kvm_check_extension(s, KVM_CAP_TSC_DEADLINE_TIMER)) {
+        env->cpuid_ext_features &= ~CPUID_EXT_TSC_DEADLINE_TIMER;
+    }
 
     env->cpuid_ext2_features &= kvm_arch_get_supported_cpuid(s, 0x80000001,
                                                              0, R_EDX);
-- 
1.7.1

