12:06 p.m.
(CCing qemu-devel and libvir-list)
On Sun, Sep 22, 2013 at 04:44:55PM +0200, Borislav Petkov wrote:
From: Borislav Petkov <bp(a)suse.de>
Add support for the KVM_GET_EMULATED_CPUID ioctl and leave feature bits
enabled, when requested by userspace, if kvm emulates them.
Signed-off-by: Borislav Petkov <bp(a)suse.de>
This will break some assumptions about the semantics of "-cpu host",
that today means "enable every single feature that can be enabled in the
host". This, in turn, breaks the assumption that "-cpu host" can be used
by libvirt to get information about all CPU features supported by the
host.
So, I have two questions:
1) Should "-cpu host" enable GET_EMULATED_CPUID features? (I believe the
answer is "no");
2) If not, we need a new mechanism to let libvirt know which features
can be enabled on a host (in a way that would allow libvirt to
easily calculate the set of possible destination hosts to which a VM
can be migrated, before deciding to migrate it).
This interface is getting complex enough for me to consider simply
asking libvirt developers to call GET_EMULATED_CPUID and
GET_SUPPORTED_CPUID directly, instead of asking QEMU for information.
But if libvirt does that, it needs a way to know if it's running a QEMU
version that supports GET_EMULATED_CPUID, or an old version that
supports only GET_SUPPORTED_CPUID.
Another alternative is to simply let libvirt ignore GET_EMULATED_CPUID
by now, and treat GET_EMULATED_CPUID features as not supported by the
host. But then it will break the use cases that prompted the creation of
GET_EMULATED_CPUID in the first place.
---
include/sysemu/kvm.h | 4 ++++
linux-headers/linux/kvm.h | 4 ++++
target-i386/cpu.c | 7 +++++++
target-i386/kvm.c | 38 ++++++++++++++++++++++++++++++++++----
4 files changed, 49 insertions(+), 4 deletions(-)
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 9bbe3db1464e..8eda1ada848a 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -265,6 +265,10 @@ int kvm_check_extension(KVMState *s, unsigned int extension);
uint32_t kvm_arch_get_supported_cpuid(KVMState *env, uint32_t function,
uint32_t index, int reg);
+
+uint32_t kvm_arch_get_emulated_cpuid(KVMState *env, uint32_t function,
+ uint32_t index, int reg);
+
void kvm_cpu_synchronize_state(CPUState *cpu);
/* generic hooks - to be moved/refactored once there are more users */
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index c614070662e1..edc8f2db1f8d 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -541,6 +541,7 @@ struct kvm_ppc_smmu_info {
#define KVM_TRACE_ENABLE __KVM_DEPRECATED_MAIN_W_0x06
#define KVM_TRACE_PAUSE __KVM_DEPRECATED_MAIN_0x07
#define KVM_TRACE_DISABLE __KVM_DEPRECATED_MAIN_0x08
+#define KVM_GET_EMULATED_CPUID _IOWR(KVMIO, 0x09, struct kvm_cpuid2)
/*
* Extension capability list.
@@ -666,6 +667,9 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_IRQ_MPIC 90
#define KVM_CAP_PPC_RTAS 91
#define KVM_CAP_IRQ_XICS 92
+#define KVM_CAP_ARM_EL1_32BIT 93
+#define KVM_CAP_SPAPR_MULTITCE 94
+#define KVM_CAP_EXT_EMUL_CPUID 95
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index c36345e426d7..5406348ceb4a 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -1850,7 +1850,14 @@ static void filter_features_for_kvm(X86CPU *cpu)
wi->cpuid_ecx,
wi->cpuid_reg);
uint32_t requested_features = env->features[w];
+
+ uint32_t emul_features = kvm_arch_get_emulated_cpuid(s, wi->cpuid_eax,
+ wi->cpuid_ecx,
+ wi->cpuid_reg);
+
env->features[w] &= host_feat;
+ env->features[w] |= (requested_features & emul_features);
+
I find the above logic confusing: you remove a few bits just to re-add
them later. Isn't easier and simpler to simply do:
env->features[w] &= (host_feat | emul_features);
?
cpu->filtered_features[w] = requested_features &
~env->features[w];
}
}
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 749aa09a21a6..7f598f01bda5 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -80,7 +80,7 @@ bool kvm_allows_irq0_override(void)
return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
}
-static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
+static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int ioctl, int max)
{
struct kvm_cpuid2 *cpuid;
int r, size;
@@ -88,7 +88,7 @@ static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
size = sizeof(*cpuid) + max * sizeof(*cpuid->entries);
cpuid = (struct kvm_cpuid2 *)g_malloc0(size);
cpuid->nent = max;
- r = kvm_ioctl(s, KVM_GET_SUPPORTED_CPUID, cpuid);
+ r = kvm_ioctl(s, ioctl, cpuid);
if (r == 0 && cpuid->nent >= max) {
r = -E2BIG;
}
@@ -97,7 +97,10 @@ static struct kvm_cpuid2 *try_get_cpuid(KVMState *s, int max)
g_free(cpuid);
return NULL;
} else {
- fprintf(stderr, "KVM_GET_SUPPORTED_CPUID failed: %s\n",
+ fprintf(stderr, "%s failed: %s\n",
+ (ioctl == (int)KVM_GET_SUPPORTED_CPUID
+ ? "KVM_GET_SUPPORTED_CPUID"
+ : "KVM_GET_EMULATED_CPUID"),
strerror(-r));
exit(1);
}
@@ -112,7 +115,17 @@ static struct kvm_cpuid2 *get_supported_cpuid(KVMState *s)
{
struct kvm_cpuid2 *cpuid;
int max = 1;
- while ((cpuid = try_get_cpuid(s, max)) == NULL) {
+ while ((cpuid = try_get_cpuid(s, KVM_GET_SUPPORTED_CPUID, max)) == NULL) {
+ max *= 2;
+ }
+ return cpuid;
+}
+
+static struct kvm_cpuid2 *get_emulated_cpuid(KVMState *s)
+{
+ struct kvm_cpuid2 *cpuid;
+ int max = 1;
+ while ((cpuid = try_get_cpuid(s, KVM_GET_EMULATED_CPUID, max)) == NULL) {
max *= 2;
}
return cpuid;
@@ -241,6 +254,23 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t
function,
return ret;
}
+uint32_t kvm_arch_get_emulated_cpuid(KVMState *s, uint32_t function,
+ uint32_t index, int reg)
+{
+ struct kvm_cpuid2 *cpuid __attribute__((unused));
+
+ if (!kvm_check_extension(s, KVM_CAP_EXT_EMUL_CPUID))
+ return 0;
+
+ cpuid = get_emulated_cpuid(s);
+
+ struct kvm_cpuid_entry2 *entry = cpuid_find_entry(cpuid, function, index);
+ if (entry)
+ return cpuid_entry_get_reg(entry, reg);
+
+ return 0;
+}
+
typedef struct HWPoisonPage {
ram_addr_t ram_addr;
QLIST_ENTRY(HWPoisonPage) list;
--
1.8.4
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Eduardo