[PATCH v2 4/7] export paravirtual cpuid flags in KVM_GET_SUPPORTED_CPUID

[Glauber Costa <glommer@redhat.com>]

Right now, we were using individual KVM_CAP entities to communicate
userspace about which cpuids we support. This is suboptimal, since it
generates a delay between the feature arriving in the host, and
being available at the guest.

A much better mechanism is to list para features in KVM_GET_SUPPORTED_CPUID.
This makes userspace automatically aware of what we provide. And if we
ever add a new cpuid bit in the future, we have to do that again,
which create some complexity and delay in feature adoption.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 arch/x86/include/asm/kvm_para.h |    4 ++++
 arch/x86/kvm/x86.c              |   27 +++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 9734808..f019f8c 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -16,6 +16,10 @@
 #define KVM_FEATURE_CLOCKSOURCE		0
 #define KVM_FEATURE_NOP_IO_DELAY	1
 #define KVM_FEATURE_MMU_OP		2
+/* This indicates that the new set of kvmclock msrs
+ * are available. The use of 0x11 and 0x12 is deprecated
+ */
+#define KVM_FEATURE_CLOCKSOURCE2        3
 
 #define MSR_KVM_WALL_CLOCK  0x11
 #define MSR_KVM_SYSTEM_TIME 0x12
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eb84947..8a7cdda 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1971,6 +1971,20 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		}
 		break;
 	}
+	case 0x40000000: {
+		char signature[] = "KVMKVMKVM";
+		u32 *sigptr = (u32 *)signature;
+		entry->eax = 1;
+		entry->ebx = sigptr[0];
+		entry->ecx = sigptr[1];
+		entry->edx = sigptr[2];
+		break;
+	}
+	case 0x40000001:
+		entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) |
+		(1 << KVM_FEATURE_NOP_IO_DELAY) |
+		(1 << KVM_FEATURE_CLOCKSOURCE2);
+		break;
 	case 0x80000000:
 		entry->eax = min(entry->eax, 0x8000001a);
 		break;
@@ -2017,6 +2031,19 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
 	for (func = 0x80000001; func <= limit && nent < cpuid->nent; ++func)
 		do_cpuid_ent(&cpuid_entries[nent], func, 0,
 			     &nent, cpuid->nent);
+
+	
+
+	r = -E2BIG;
+	if (nent >= cpuid->nent)
+		goto out_free;
+
+	do_cpuid_ent(&cpuid_entries[nent], 0x40000000, 0, &nent, cpuid->nent);
+	limit = cpuid_entries[nent - 1].eax;
+	for (func = 0x40000001; func <= limit && nent < cpuid->nent; ++func)
+		do_cpuid_ent(&cpuid_entries[nent], func, 0,
+			     &nent, cpuid->nent);
+
 	r = -E2BIG;
 	if (nent >= cpuid->nent)
 		goto out_free;
-- 
1.6.2.2