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

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();

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