Enable KVM PV EOI by default. You can still disable it with
-kvm_pv_eoi cpu flag. To avoid breaking cross-version migration,
enable only for qemu 1.3 (or in the future, newer) machine type.
Note:
There don't seem to be any security-related downsides to this patch
because all this does is tell guest about the feature in a convenient
way. A well behaved guest doesn't use a feature unless it's listed but
that's irrelevant for security.
In my testing, with this patch, performance always improved with
no regressions.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
Changes from v3:
rebased on top of master. document security implications
Changes from v2:
Address comments by Andreas:
whitespace fixes and moving function around
Changes from v1:
Address comments by Eduardo:
use include instead of duplicate definition
reduce ifdef spagetti in code using features mask
rename init from _pv_eoi to _1_3 to enable adding
more stuff in this version
hw/pc_piix.c | 9 ++++++++-
target-i386/cpu.c | 33 ++++++++++++++++++++-------------
target-i386/cpu.h | 2 ++
3 files changed, 30 insertions(+), 14 deletions(-)
diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index bf04a42..1f040cb 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -43,6 +43,7 @@
#include "xen.h"
#include "memory.h"
#include "exec-memory.h"
+#include "cpu.h"
#ifdef CONFIG_XEN
# include <xen/hvm/hvm_info_table.h>
#endif
@@ -302,6 +303,12 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
initrd_filename, cpu_model, 1, 1);
}
+static void pc_init_pci_1_3(QEMUMachineInitArgs *args)
+{
+ enable_kvm_pv_eoi();
+ pc_init_pci(args);
+}
+
static void pc_init_pci_no_kvmclock(QEMUMachineInitArgs *args)
{
ram_addr_t ram_size = args->ram_size;
@@ -349,7 +356,7 @@ static QEMUMachine pc_machine_v1_3 = {
.name = "pc-1.3",
.alias = "pc",
.desc = "Standard PC",
- .init = pc_init_pci,
+ .init = pc_init_pci_1_3,
.max_cpus = 255,
.is_default = 1,
};
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index f3708e6..0f77449 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -124,6 +124,25 @@ typedef struct model_features_t {
int check_cpuid = 0;
int enforce_cpuid = 0;
+#if defined(CONFIG_KVM)
+static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
+ (1 << KVM_FEATURE_NOP_IO_DELAY) |
+ (1 << KVM_FEATURE_MMU_OP) |
+ (1 << KVM_FEATURE_CLOCKSOURCE2) |
+ (1 << KVM_FEATURE_ASYNC_PF) |
+ (1 << KVM_FEATURE_STEAL_TIME) |
+ (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
+static const uint32_t kvm_pv_eoi_features = (0x1 << KVM_FEATURE_PV_EOI);
+#else
+static uint32_t kvm_default_features = 0;
+static const uint32_t kvm_pv_eoi_features = 0;
+#endif
+
+void enable_kvm_pv_eoi(void)
+{
+ kvm_default_features |= kvm_pv_eoi_features;
+}
+
void host_cpuid(uint32_t function, uint32_t count,
uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
{
@@ -1107,7 +1126,7 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def,
const char *cpu_model)
/* Features to be added*/
uint32_t plus_features = 0, plus_ext_features = 0;
uint32_t plus_ext2_features = 0, plus_ext3_features = 0;
- uint32_t plus_kvm_features = 0, plus_svm_features = 0;
+ uint32_t plus_kvm_features = kvm_default_features, plus_svm_features = 0;
uint32_t plus_7_0_ebx_features = 0;
/* Features to be removed */
uint32_t minus_features = 0, minus_ext_features = 0;
@@ -1127,18 +1146,6 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def,
const char *cpu_model)
memcpy(x86_cpu_def, def, sizeof(*def));
}
-#if defined(CONFIG_KVM)
- plus_kvm_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
- (1 << KVM_FEATURE_NOP_IO_DELAY) |
- (1 << KVM_FEATURE_MMU_OP) |
- (1 << KVM_FEATURE_CLOCKSOURCE2) |
- (1 << KVM_FEATURE_ASYNC_PF) |
- (1 << KVM_FEATURE_STEAL_TIME) |
- (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
-#else
- plus_kvm_features = 0;
-#endif
-
add_flagname_to_bitmaps("hypervisor", &plus_features,
&plus_ext_features, &plus_ext2_features, &plus_ext3_features,
&plus_kvm_features, &plus_svm_features, &plus_7_0_ebx_features);
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 871c270..de33303 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -1188,4 +1188,6 @@ void do_smm_enter(CPUX86State *env1);
void cpu_report_tpr_access(CPUX86State *env, TPRAccess access);
+void enable_kvm_pv_eoi(void);
+
#endif /* CPU_I386_H */
--
MST
