[PATCH v3 0/8] [PATCH v3 0/8] target/i386: Misc cleanup on KVM PV defs, outdated comments and error handling

[PATCH v3 0/8] [PATCH v3 0/8] target/i386: Misc cleanup on KVM PV defs, outdated comments and error handling

[Zhao Liu]

Hi,

This is my v3 cleanup series. Compared with v2 [1],
 * v3 resolved the rebasing conflict (now based on 37fbfda8f414).
 * Added 2 more patches (patch 7&8) to clean up error handling in
   kvm_arch_init().


Background and Introduction
===========================

This series picks cleanup from my previous kvmclock [2] (as other
renaming attempts were temporarily put on hold).

In addition, this series also include the cleanup on a historically
workaround, recent comment of coco interface [3] and error handling
corner cases in kvm_arch_init().

Avoiding the fragmentation of these misc cleanups, I consolidated them
all in one series and was able to tackle them in one go!

[1]: https://lore.kernel.org/qemu-devel/20240506085153.2834841-1-zhao1.liu@intel.com/
[2]: https://lore.kernel.org/qemu-devel/20240329101954.3954987-1-zhao1.liu@linux.intel.com/
[3]: https://lore.kernel.org/qemu-devel/2815f0f1-9e20-4985-849c-d74c6cdc94ae@intel.com/

Thanks and Best Regards,
Zhao
---
Zhao Liu (8):
  target/i386/kvm: Add feature bit definitions for KVM CPUID
  target/i386/kvm: Remove local MSR_KVM_WALL_CLOCK and
    MSR_KVM_SYSTEM_TIME definitions
  target/i386/kvm: Only save/load kvmclock MSRs when kvmclock enabled
  target/i386/kvm: Save/load MSRs of kvmclock2
    (KVM_FEATURE_CLOCKSOURCE2)
  target/i386/kvm: Drop workaround for KVM_X86_DISABLE_EXITS_HTL typo
  target/i386/confidential-guest: Fix comment of
    x86_confidential_guest_kvm_type()
  target/i386/kvm: Clean up return values of MSR filter related
    functions
  target/i386/kvm: Clean up error handling in kvm_arch_init()

 hw/i386/kvm/clock.c              |   5 +-
 target/i386/confidential-guest.h |   2 +-
 target/i386/cpu.h                |  25 +++++++
 target/i386/kvm/kvm.c            | 108 ++++++++++++++++++-------------
 target/i386/kvm/kvm_i386.h       |   4 +-
 5 files changed, 92 insertions(+), 52 deletions(-)

-- 
2.34.1

[PATCH v3 1/8] target/i386/kvm: Add feature bit definitions for KVM CPUID

[Zhao Liu]

Add feature definitions for KVM_CPUID_FEATURES in CPUID (
CPUID[4000_0001].EAX and CPUID[4000_0001].EDX), to get rid of lots of
offset calculations.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
v3: Resolved a rebasing conflict.
v2: Changed the prefix from CPUID_FEAT_KVM_* to CPUID_KVM_*. (Xiaoyao)
---
 hw/i386/kvm/clock.c   |  5 ++---
 target/i386/cpu.h     | 23 +++++++++++++++++++++++
 target/i386/kvm/kvm.c | 28 ++++++++++++++--------------
 3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 40aa9a32c32c..ce416c05a3d0 100644
--- a/hw/i386/kvm/clock.c
+++ b/hw/i386/kvm/clock.c
@@ -27,7 +27,6 @@
 #include "qapi/error.h"
 
 #include <linux/kvm.h>
-#include "standard-headers/asm-x86/kvm_para.h"
 #include "qom/object.h"
 
 #define TYPE_KVM_CLOCK "kvmclock"
@@ -334,8 +333,8 @@ void kvmclock_create(bool create_always)
 
     assert(kvm_enabled());
     if (create_always ||
-        cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
-                                       (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
+        cpu->env.features[FEAT_KVM] & (CPUID_KVM_CLOCK |
+                                       CPUID_KVM_CLOCK2)) {
         sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL);
     }
 }
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index c43ac01c794a..b59bdc1c9d9d 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -28,6 +28,7 @@
 #include "qapi/qapi-types-common.h"
 #include "qemu/cpu-float.h"
 #include "qemu/timer.h"
+#include "standard-headers/asm-x86/kvm_para.h"
 
 #define XEN_NR_VIRQS 24
 
@@ -988,6 +989,28 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
 #define CPUID_8000_0007_EBX_OVERFLOW_RECOV    (1U << 0)
 #define CPUID_8000_0007_EBX_SUCCOR      (1U << 1)
 
+/* (Old) KVM paravirtualized clocksource */
+#define CPUID_KVM_CLOCK            (1U << KVM_FEATURE_CLOCKSOURCE)
+/* (New) KVM specific paravirtualized clocksource */
+#define CPUID_KVM_CLOCK2           (1U << KVM_FEATURE_CLOCKSOURCE2)
+/* KVM asynchronous page fault */
+#define CPUID_KVM_ASYNCPF          (1U << KVM_FEATURE_ASYNC_PF)
+/* KVM stolen (when guest vCPU is not running) time accounting */
+#define CPUID_KVM_STEAL_TIME       (1U << KVM_FEATURE_STEAL_TIME)
+/* KVM paravirtualized end-of-interrupt signaling */
+#define CPUID_KVM_PV_EOI           (1U << KVM_FEATURE_PV_EOI)
+/* KVM paravirtualized spinlocks support */
+#define CPUID_KVM_PV_UNHALT        (1U << KVM_FEATURE_PV_UNHALT)
+/* KVM host-side polling on HLT control from the guest */
+#define CPUID_KVM_POLL_CONTROL     (1U << KVM_FEATURE_POLL_CONTROL)
+/* KVM interrupt based asynchronous page fault*/
+#define CPUID_KVM_ASYNCPF_INT      (1U << KVM_FEATURE_ASYNC_PF_INT)
+/* KVM 'Extended Destination ID' support for external interrupts */
+#define CPUID_KVM_MSI_EXT_DEST_ID  (1U << KVM_FEATURE_MSI_EXT_DEST_ID)
+
+/* Hint to KVM that vCPUs expect never preempted for an unlimited time */
+#define CPUID_KVM_HINTS_REALTIME    (1U << KVM_HINTS_REALTIME)
+
 /* CLZERO instruction */
 #define CPUID_8000_0008_EBX_CLZERO      (1U << 0)
 /* Always save/restore FP error pointers */
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index becca2efa5b4..86e42beb78bf 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -539,13 +539,13 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
          * be enabled without the in-kernel irqchip
          */
         if (!kvm_irqchip_in_kernel()) {
-            ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
+            ret &= ~CPUID_KVM_PV_UNHALT;
         }
         if (kvm_irqchip_is_split()) {
-            ret |= 1U << KVM_FEATURE_MSI_EXT_DEST_ID;
+            ret |= CPUID_KVM_MSI_EXT_DEST_ID;
         }
     } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
-        ret |= 1U << KVM_HINTS_REALTIME;
+        ret |= CPUID_KVM_HINTS_REALTIME;
     }
 
     if (current_machine->cgs) {
@@ -3424,20 +3424,20 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
         kvm_msr_entry_add(cpu, MSR_IA32_TSC, env->tsc);
         kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
         kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
-        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF_INT)) {
+        if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
             kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, env->async_pf_int_msr);
         }
-        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF)) {
+        if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF) {
             kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr);
         }
-        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_PV_EOI)) {
+        if (env->features[FEAT_KVM] & CPUID_KVM_PV_EOI) {
             kvm_msr_entry_add(cpu, MSR_KVM_PV_EOI_EN, env->pv_eoi_en_msr);
         }
-        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_STEAL_TIME)) {
+        if (env->features[FEAT_KVM] & CPUID_KVM_STEAL_TIME) {
             kvm_msr_entry_add(cpu, MSR_KVM_STEAL_TIME, env->steal_time_msr);
         }
 
-        if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_POLL_CONTROL)) {
+        if (env->features[FEAT_KVM] & CPUID_KVM_POLL_CONTROL) {
             kvm_msr_entry_add(cpu, MSR_KVM_POLL_CONTROL, env->poll_control_msr);
         }
 
@@ -3900,19 +3900,19 @@ static int kvm_get_msrs(X86CPU *cpu)
 #endif
     kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
     kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
-    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF_INT)) {
+    if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
         kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, 0);
     }
-    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF)) {
+    if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF) {
         kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_EN, 0);
     }
-    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_PV_EOI)) {
+    if (env->features[FEAT_KVM] & CPUID_KVM_PV_EOI) {
         kvm_msr_entry_add(cpu, MSR_KVM_PV_EOI_EN, 0);
     }
-    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_STEAL_TIME)) {
+    if (env->features[FEAT_KVM] & CPUID_KVM_STEAL_TIME) {
         kvm_msr_entry_add(cpu, MSR_KVM_STEAL_TIME, 0);
     }
-    if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_POLL_CONTROL)) {
+    if (env->features[FEAT_KVM] & CPUID_KVM_POLL_CONTROL) {
         kvm_msr_entry_add(cpu, MSR_KVM_POLL_CONTROL, 1);
     }
     if (has_architectural_pmu_version > 0) {
@@ -5613,7 +5613,7 @@ uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address)
         return address;
     }
     env = &X86_CPU(first_cpu)->env;
-    if (!(env->features[FEAT_KVM] & (1 << KVM_FEATURE_MSI_EXT_DEST_ID))) {
+    if (!(env->features[FEAT_KVM] & CPUID_KVM_MSI_EXT_DEST_ID)) {
         return address;
     }
 
-- 
2.34.1

[PATCH v3 2/8] target/i386/kvm: Remove local MSR_KVM_WALL_CLOCK and MSR_KVM_SYSTEM_TIME definitions

[Zhao Liu]

These 2 MSRs have been already defined in kvm_para.h (standard-headers/
asm-x86/kvm_para.h).

Remove QEMU local definitions to avoid duplication.

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/kvm/kvm.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 86e42beb78bf..6ad5a7dbf1fd 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -81,9 +81,6 @@
 #define KVM_APIC_BUS_CYCLE_NS       1
 #define KVM_APIC_BUS_FREQUENCY      (1000000000ULL / KVM_APIC_BUS_CYCLE_NS)
 
-#define MSR_KVM_WALL_CLOCK  0x11
-#define MSR_KVM_SYSTEM_TIME 0x12
-
 /* A 4096-byte buffer can hold the 8-byte kvm_msrs header, plus
  * 255 kvm_msr_entry structs */
 #define MSR_BUF_SIZE 4096
-- 
2.34.1

[PATCH v3 3/8] target/i386/kvm: Only save/load kvmclock MSRs when kvmclock enabled

[Zhao Liu]

MSR_KVM_SYSTEM_TIME and MSR_KVM_WALL_CLOCK are attached with the (old)
kvmclock feature (KVM_FEATURE_CLOCKSOURCE).

So, just save/load them only when kvmclock (KVM_FEATURE_CLOCKSOURCE) is
enabled.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/kvm/kvm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 6ad5a7dbf1fd..ac434e83b64c 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3419,8 +3419,10 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
      */
     if (level >= KVM_PUT_RESET_STATE) {
         kvm_msr_entry_add(cpu, MSR_IA32_TSC, env->tsc);
-        kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
-        kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+        if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK) {
+            kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
+            kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+        }
         if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
             kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, env->async_pf_int_msr);
         }
@@ -3895,8 +3897,10 @@ static int kvm_get_msrs(X86CPU *cpu)
         }
     }
 #endif
-    kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
-    kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
+    if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK) {
+        kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
+        kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
+    }
     if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
         kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, 0);
     }
-- 
2.34.1

[PATCH v3 4/8] target/i386/kvm: Save/load MSRs of kvmclock2 (KVM_FEATURE_CLOCKSOURCE2)

[Zhao Liu]

MSR_KVM_SYSTEM_TIME_NEW and MSR_KVM_WALL_CLOCK_NEW are bound to
kvmclock2 (KVM_FEATURE_CLOCKSOURCE2).

Add the save/load support for these 2 MSRs just like kvmclock MSRs.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/cpu.h     |  2 ++
 target/i386/kvm/kvm.c | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index b59bdc1c9d9d..35dc68631989 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1826,6 +1826,8 @@ typedef struct CPUArchState {
 
     uint64_t system_time_msr;
     uint64_t wall_clock_msr;
+    uint64_t system_time_new_msr;
+    uint64_t wall_clock_new_msr;
     uint64_t steal_time_msr;
     uint64_t async_pf_en_msr;
     uint64_t async_pf_int_msr;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ac434e83b64c..64e54beac7b3 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -3423,6 +3423,12 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
             kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
             kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
         }
+        if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK2) {
+            kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME_NEW,
+                              env->system_time_new_msr);
+            kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK_NEW,
+                              env->wall_clock_new_msr);
+        }
         if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
             kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, env->async_pf_int_msr);
         }
@@ -3901,6 +3907,10 @@ static int kvm_get_msrs(X86CPU *cpu)
         kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
         kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
     }
+    if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK2) {
+        kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME_NEW, 0);
+        kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK_NEW, 0);
+    }
     if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
         kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, 0);
     }
@@ -4167,6 +4177,12 @@ static int kvm_get_msrs(X86CPU *cpu)
         case MSR_KVM_WALL_CLOCK:
             env->wall_clock_msr = msrs[i].data;
             break;
+        case MSR_KVM_SYSTEM_TIME_NEW:
+            env->system_time_new_msr = msrs[i].data;
+            break;
+        case MSR_KVM_WALL_CLOCK_NEW:
+            env->wall_clock_new_msr = msrs[i].data;
+            break;
         case MSR_MCG_STATUS:
             env->mcg_status = msrs[i].data;
             break;
-- 
2.34.1

[PATCH v3 5/8] target/i386/kvm: Drop workaround for KVM_X86_DISABLE_EXITS_HTL typo

[Zhao Liu]

The KVM_X86_DISABLE_EXITS_HTL typo has been fixed in commit
77d361b13c19 ("linux-headers: Update to kernel mainline commit
b357bf602").

Drop the related workaround.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/kvm/kvm.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 64e54beac7b3..4aae4ffc9ccd 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2728,10 +2728,6 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
 
     if (enable_cpu_pm) {
         int disable_exits = kvm_check_extension(s, KVM_CAP_X86_DISABLE_EXITS);
-/* Work around for kernel header with a typo. TODO: fix header and drop. */
-#if defined(KVM_X86_DISABLE_EXITS_HTL) && !defined(KVM_X86_DISABLE_EXITS_HLT)
-#define KVM_X86_DISABLE_EXITS_HLT KVM_X86_DISABLE_EXITS_HTL
-#endif
         if (disable_exits) {
             disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
                               KVM_X86_DISABLE_EXITS_HLT |
-- 
2.34.1

[PATCH v3 6/8] target/i386/confidential-guest: Fix comment of x86_confidential_guest_kvm_type()

[Zhao Liu]

Update the comment to match the X86ConfidentialGuestClass
implementation.

Reported-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
---
 target/i386/confidential-guest.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/confidential-guest.h b/target/i386/confidential-guest.h
index 7342d2843aa5..c90a59bac41a 100644
--- a/target/i386/confidential-guest.h
+++ b/target/i386/confidential-guest.h
@@ -46,7 +46,7 @@ struct X86ConfidentialGuestClass {
 /**
  * x86_confidential_guest_kvm_type:
  *
- * Calls #X86ConfidentialGuestClass.unplug callback of @plug_handler.
+ * Calls #X86ConfidentialGuestClass.kvm_type() callback.
  */
 static inline int x86_confidential_guest_kvm_type(X86ConfidentialGuest *cg)
 {
-- 
2.34.1

[PATCH v3 7/8] target/i386/kvm: Clean up return values of MSR filter related functions

[Zhao Liu]

At present, the error code of MSR filter enablement is attempted to be
printed in error_report().

Unfortunately, this behavior doesn't work because the MSR filter-related
functions return the boolean and current error_report() use the wrong
return value.

So fix this by making MSR filter related functions return int type and
printing such returned value in error_report().

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/kvm/kvm.c      | 35 +++++++++++++++++------------------
 target/i386/kvm/kvm_i386.h |  4 ++--
 2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 4aae4ffc9ccd..0fd1d099ae4c 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2780,8 +2780,6 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
             }
     }
     if (kvm_vm_check_extension(s, KVM_CAP_X86_USER_SPACE_MSR)) {
-        bool r;
-
         ret = kvm_vm_enable_cap(s, KVM_CAP_X86_USER_SPACE_MSR, 0,
                                 KVM_MSR_EXIT_REASON_FILTER);
         if (ret) {
@@ -2790,9 +2788,9 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
             exit(1);
         }
 
-        r = kvm_filter_msr(s, MSR_CORE_THREAD_COUNT,
-                           kvm_rdmsr_core_thread_count, NULL);
-        if (!r) {
+        ret = kvm_filter_msr(s, MSR_CORE_THREAD_COUNT,
+                             kvm_rdmsr_core_thread_count, NULL);
+        if (ret) {
             error_report("Could not install MSR_CORE_THREAD_COUNT handler: %s",
                          strerror(-ret));
             exit(1);
@@ -5274,13 +5272,13 @@ void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
     }
 }
 
-static bool kvm_install_msr_filters(KVMState *s)
+static int kvm_install_msr_filters(KVMState *s)
 {
     uint64_t zero = 0;
     struct kvm_msr_filter filter = {
         .flags = KVM_MSR_FILTER_DEFAULT_ALLOW,
     };
-    int r, i, j = 0;
+    int ret, i, j = 0;
 
     for (i = 0; i < KVM_MSR_FILTER_MAX_RANGES; i++) {
         KVMMSRHandlers *handler = &msr_handlers[i];
@@ -5304,18 +5302,18 @@ static bool kvm_install_msr_filters(KVMState *s)
         }
     }
 
-    r = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
-    if (r) {
-        return false;
+    ret = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
+    if (ret) {
+        return ret;
     }
 
-    return true;
+    return 0;
 }
 
-bool kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
-                    QEMUWRMSRHandler *wrmsr)
+int kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
+                   QEMUWRMSRHandler *wrmsr)
 {
-    int i;
+    int i, ret;
 
     for (i = 0; i < ARRAY_SIZE(msr_handlers); i++) {
         if (!msr_handlers[i].msr) {
@@ -5325,16 +5323,17 @@ bool kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
                 .wrmsr = wrmsr,
             };
 
-            if (!kvm_install_msr_filters(s)) {
+            ret = kvm_install_msr_filters(s);
+            if (ret) {
                 msr_handlers[i] = (KVMMSRHandlers) { };
-                return false;
+                return ret;
             }
 
-            return true;
+            return 0;
         }
     }
 
-    return false;
+    return 0;
 }
 
 static int kvm_handle_rdmsr(X86CPU *cpu, struct kvm_run *run)
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 34fc60774b86..91c2d6e69163 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -74,8 +74,8 @@ typedef struct kvm_msr_handlers {
     QEMUWRMSRHandler *wrmsr;
 } KVMMSRHandlers;
 
-bool kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
-                    QEMUWRMSRHandler *wrmsr);
+int kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
+                   QEMUWRMSRHandler *wrmsr);
 
 #endif /* CONFIG_KVM */
 
-- 
2.34.1

[PATCH v3 8/8] target/i386/kvm: Clean up error handling in kvm_arch_init()

[Zhao Liu]

Currently, there're following incorrect error handling cases in
kvm_arch_init():
* Missed to handle failure of kvm_get_supported_feature_msrs().
* Missed to return when KVM_CAP_X86_DISABLE_EXITS enabling fails.
* MSR filter related cases called exit() directly instead of returning
  to kvm_init().

Fix the above cases.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 target/i386/kvm/kvm.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 0fd1d099ae4c..246fe12ae411 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2682,7 +2682,10 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         return ret;
     }
 
-    kvm_get_supported_feature_msrs(s);
+    ret = kvm_get_supported_feature_msrs(s);
+    if (ret < 0) {
+        return ret;
+    }
 
     uname(&utsname);
     lm_capable_kernel = strcmp(utsname.machine, "x86_64") == 0;
@@ -2740,6 +2743,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         if (ret < 0) {
             error_report("kvm: guest stopping CPU not supported: %s",
                          strerror(-ret));
+            return ret;
         }
     }
 
@@ -2785,7 +2789,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         if (ret) {
             error_report("Could not enable user space MSRs: %s",
                          strerror(-ret));
-            exit(1);
+            return ret;
         }
 
         ret = kvm_filter_msr(s, MSR_CORE_THREAD_COUNT,
@@ -2793,7 +2797,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         if (ret) {
             error_report("Could not install MSR_CORE_THREAD_COUNT handler: %s",
                          strerror(-ret));
-            exit(1);
+            return ret;
         }
     }
 
-- 
2.34.1

Re: [PATCH v3 7/8] target/i386/kvm: Clean up return values of MSR filter related functions

[Chen, Zide]

On 7/14/2024 9:49 PM, Zhao Liu wrote:
> @@ -5274,13 +5272,13 @@ void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
>      }
>  }
>  
> -static bool kvm_install_msr_filters(KVMState *s)
> +static int kvm_install_msr_filters(KVMState *s)
>  {
>      uint64_t zero = 0;
>      struct kvm_msr_filter filter = {
>          .flags = KVM_MSR_FILTER_DEFAULT_ALLOW,
>      };
> -    int r, i, j = 0;
> +    int ret, i, j = 0;
>  
>      for (i = 0; i < KVM_MSR_FILTER_MAX_RANGES; i++) {

Nit: Since it's a clean up patch, how about replace
KVM_MSR_FILTER_MAX_RANGES with ARRAY_SIZE(msr_handlers), to make the
code consistent in other places to refer to the array size of
msr_handlers[].

>          KVMMSRHandlers *handler = &msr_handlers[i];
> @@ -5304,18 +5302,18 @@ static bool kvm_install_msr_filters(KVMState *s)
>          }
>      }
>  
> -    r = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
> -    if (r) {
> -        return false;
> +    ret = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
> +    if (ret) {
> +        return ret;
>      }
>  
> -    return true;
> +    return 0;
>  }

Nit: Seems ret is not needed here, and can directly return kvm_vm_ioctl();

Re: [PATCH v3 7/8] target/i386/kvm: Clean up return values of MSR filter related functions

[Zhao Liu]

Hi Zide,

On Mon, Jul 15, 2024 at 03:18:07PM -0700, Chen, Zide wrote:
> Date: Mon, 15 Jul 2024 15:18:07 -0700
> From: "Chen, Zide" <zide.chen@intel.com>
> Subject: Re: [PATCH v3 7/8] target/i386/kvm: Clean up return values of MSR
>  filter related functions
> 
> On 7/14/2024 9:49 PM, Zhao Liu wrote:
> > @@ -5274,13 +5272,13 @@ void kvm_arch_update_guest_debug(CPUState *cpu, struct kvm_guest_debug *dbg)
> >      }
> >  }
> >  
> > -static bool kvm_install_msr_filters(KVMState *s)
> > +static int kvm_install_msr_filters(KVMState *s)
> >  {
> >      uint64_t zero = 0;
> >      struct kvm_msr_filter filter = {
> >          .flags = KVM_MSR_FILTER_DEFAULT_ALLOW,
> >      };
> > -    int r, i, j = 0;
> > +    int ret, i, j = 0;
> >  
> >      for (i = 0; i < KVM_MSR_FILTER_MAX_RANGES; i++) {
> 
> Nit: Since it's a clean up patch, how about replace
> KVM_MSR_FILTER_MAX_RANGES with ARRAY_SIZE(msr_handlers), to make the
> code consistent in other places to refer to the array size of
> msr_handlers[].

Yes, that's fine, I'll add a new small trivial patch to clean up this.

> >          KVMMSRHandlers *handler = &msr_handlers[i];
> > @@ -5304,18 +5302,18 @@ static bool kvm_install_msr_filters(KVMState *s)
> >          }
> >      }
> >  
> > -    r = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
> > -    if (r) {
> > -        return false;
> > +    ret = kvm_vm_ioctl(s, KVM_X86_SET_MSR_FILTER, &filter);
> > +    if (ret) {
> > +        return ret;
> >      }
> >  
> > -    return true;
> > +    return 0;
> >  }
> 
> Nit: Seems ret is not needed here, and can directly return kvm_vm_ioctl();

Yes, good catch!

Thanks for you review!
Zhao