[v4] Introduce support for confidential guest reset (x86)

[PATCH v4 01/31] i386/kvm: avoid installing duplicate msr entries in msr_handlers

Ani Sinha posted 31 patches 1 month, 4 weeks ago

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Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>, "Michael S. Tsirkin" <mst@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Bernhard Beschow <shentey@gmail.com>, Alex Williamson <alex@shazbot.org>, "Cédric Le Goater" <clg@redhat.com>, Peter Xu <peterx@redhat.com>, Ani Sinha <anisinha@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, David Woodhouse <dwmw2@infradead.org>, Paul Durrant <paul@xen.org>

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[PATCH v4 01/31] i386/kvm: avoid installing duplicate msr entries in msr_handlers

Posted by Ani Sinha 1 month, 4 weeks ago

kvm_filter_msr() does not check if an msr entry is already present in the
msr_handlers table and installs a new handler unconditionally. If the function
is called again with the same MSR, it will result in duplicate entries in the
table and multiple such calls will fill up the table needlessly. Fix that.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 target/i386/kvm/kvm.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 0c940d4b64..da1ed3b62a 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -6042,27 +6042,33 @@ static int kvm_install_msr_filters(KVMState *s)
 static int kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
                           QEMUWRMSRHandler *wrmsr)
 {
-    int i, ret;
+    int i, ret = 0;
 
     for (i = 0; i < ARRAY_SIZE(msr_handlers); i++) {
-        if (!msr_handlers[i].msr) {
+        if (msr_handlers[i].msr == msr) {
+            break;
+        } else if (!msr_handlers[i].msr) {
             msr_handlers[i] = (KVMMSRHandlers) {
                 .msr = msr,
                 .rdmsr = rdmsr,
                 .wrmsr = wrmsr,
             };
+            break;
+        }
+    }
 
-            ret = kvm_install_msr_filters(s);
-            if (ret) {
-                msr_handlers[i] = (KVMMSRHandlers) { };
-                return ret;
-            }
+    if (i == ARRAY_SIZE(msr_handlers)) {
+        ret = -EINVAL;
+        goto end;
+    }
 
-            return 0;
-        }
+    ret = kvm_install_msr_filters(s);
+    if (ret) {
+        msr_handlers[i] = (KVMMSRHandlers) { };
     }
 
-    return -EINVAL;
+ end:
+    return ret;
 }
 
 static int kvm_handle_rdmsr(X86CPU *cpu, struct kvm_run *run)
-- 
2.42.0