Re: [PATCH v2] KVM: X86: Fix initialization of MSR lists(msrs_to_save[], emulated_msrs[] and msr_based_features[])

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Ping for comments :)

On 11/6/2019 2:35 PM, Chenyi Qiang wrote:
The three MSR lists(msrs_to_save[], emulated_msrs[] and
msr_based_features[]) are global arrays of kvm.ko, which are
adjusted (copy supported MSRs forward to override the unsupported MSRs)
when insmod kvm-{intel,amd}.ko, but it doesn't reset these three arrays
to their initial value when rmmod kvm-{intel,amd}.ko. Thus, at the next
installation, kvm-{intel,amd}.ko will do operations on the modified
arrays with some MSRs lost and some MSRs duplicated.

So define three constant arrays to hold the initial MSR lists and
initialize msrs_to_save[], emulated_msrs[] and msr_based_features[]
based on the constant arrays.

Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
---
Changes in v2:
  - define initial MSR lists with static const.
  - change the dynamic allocation of supported MSR lists to static allocation.

  arch/x86/kvm/x86.c | 51 +++++++++++++++++++++++++---------------------
  1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 89621025577a..0b4b6db5b13f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1138,13 +1138,15 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
   * List of msr numbers which we expose to userspace through KVM_GET_MSRS
   * and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.
   *
- * This list is modified at module load time to reflect the
+ * The three MSR lists(msrs_to_save, emulated_msrs, msr_based_features)
+ * extract the supported MSRs from the related const lists.
+ * msrs_to_save is selected from the msrs_to_save_all to reflect the
   * capabilities of the host cpu. This capabilities test skips MSRs that are
- * kvm-specific. Those are put in emulated_msrs; filtering of emulated_msrs
+ * kvm-specific. Those are put in emulated_msrs_all; filtering of emulated_msrs
   * may depend on host virtualization features rather than host cpu features.
   */
-static u32 msrs_to_save[] = {
+static const u32 msrs_to_save_all[] = {
  	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
  	MSR_STAR,
  #ifdef CONFIG_X86_64
@@ -1185,9 +1187,10 @@ static u32 msrs_to_save[] = {
  	MSR_ARCH_PERFMON_EVENTSEL0 + 16, MSR_ARCH_PERFMON_EVENTSEL0 + 17,
  };
+static u32 msrs_to_save[ARRAY_SIZE(msrs_to_save_all)];
  static unsigned num_msrs_to_save;
-static u32 emulated_msrs[] = {
+static const u32 emulated_msrs_all[] = {
  	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
  	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
  	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
@@ -1226,7 +1229,7 @@ static u32 emulated_msrs[] = {
  	 * by arch/x86/kvm/vmx/nested.c based on CPUID or other MSRs.
  	 * We always support the "true" VMX control MSRs, even if the host
  	 * processor does not, so I am putting these registers here rather
-	 * than in msrs_to_save.
+	 * than in msrs_to_save_all.
  	 */
  	MSR_IA32_VMX_BASIC,
  	MSR_IA32_VMX_TRUE_PINBASED_CTLS,
@@ -1245,13 +1248,14 @@ static u32 emulated_msrs[] = {
  	MSR_KVM_POLL_CONTROL,
  };
+static u32 emulated_msrs[ARRAY_SIZE(emulated_msrs_all)];
  static unsigned num_emulated_msrs;
/*
   * List of msr numbers which are used to expose MSR-based features that
   * can be used by a hypervisor to validate requested CPU features.
   */
-static u32 msr_based_features[] = {
+static const u32 msr_based_features_all[] = {
  	MSR_IA32_VMX_BASIC,
  	MSR_IA32_VMX_TRUE_PINBASED_CTLS,
  	MSR_IA32_VMX_PINBASED_CTLS,
@@ -1276,6 +1280,7 @@ static u32 msr_based_features[] = {
  	MSR_IA32_ARCH_CAPABILITIES,
  };
+static u32 msr_based_features[ARRAY_SIZE(msr_based_features_all)];
  static unsigned int num_msr_based_features;
static u64 kvm_get_arch_capabilities(void)
@@ -5131,19 +5136,19 @@ static void kvm_init_msr_list(void)
  	unsigned i, j;
BUILD_BUG_ON_MSG(INTEL_PMC_MAX_FIXED != 4,
-			 "Please update the fixed PMCs in msrs_to_save[]");
+			 "Please update the fixed PMCs in msrs_to_saved_all[]");
perf_get_x86_pmu_capability(&x86_pmu); - for (i = j = 0; i < ARRAY_SIZE(msrs_to_save); i++) {
-		if (rdmsr_safe(msrs_to_save[i], &dummy[0], &dummy[1]) < 0)
+	for (i = j = 0; i < ARRAY_SIZE(msrs_to_save_all); i++) {
+		if (rdmsr_safe(msrs_to_save_all[i], &dummy[0], &dummy[1]) < 0)
  			continue;
/*
  		 * Even MSRs that are valid in the host may not be exposed
  		 * to the guests in some cases.
  		 */
-		switch (msrs_to_save[i]) {
+		switch (msrs_to_save_all[i]) {
  		case MSR_IA32_BNDCFGS:
  			if (!kvm_mpx_supported())
  				continue;
@@ -5171,17 +5176,17 @@ static void kvm_init_msr_list(void)
  			break;
  		case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B: {
  			if (!kvm_x86_ops->pt_supported() ||
-				msrs_to_save[i] - MSR_IA32_RTIT_ADDR0_A >=
+				msrs_to_save_all[i] - MSR_IA32_RTIT_ADDR0_A >=
  				intel_pt_validate_hw_cap(PT_CAP_num_address_ranges) * 2)
  				continue;
  			break;
  		case MSR_ARCH_PERFMON_PERFCTR0 ... MSR_ARCH_PERFMON_PERFCTR0 + 17:
-			if (msrs_to_save[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
+			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
  			    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
  				continue;
  			break;
  		case MSR_ARCH_PERFMON_EVENTSEL0 ... MSR_ARCH_PERFMON_EVENTSEL0 + 17:
-			if (msrs_to_save[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
+			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
  			    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
  				continue;
  		}
@@ -5189,31 +5194,31 @@ static void kvm_init_msr_list(void)
  			break;
  		}
- if (j < i)
-			msrs_to_save[j] = msrs_to_save[i];
+		if (j <= i)
+			msrs_to_save[j] = msrs_to_save_all[i];
  		j++;
  	}
  	num_msrs_to_save = j;
- for (i = j = 0; i < ARRAY_SIZE(emulated_msrs); i++) {
-		if (!kvm_x86_ops->has_emulated_msr(emulated_msrs[i]))
+	for (i = j = 0; i < ARRAY_SIZE(emulated_msrs_all); i++) {
+		if (!kvm_x86_ops->has_emulated_msr(emulated_msrs_all[i]))
  			continue;
- if (j < i)
-			emulated_msrs[j] = emulated_msrs[i];
+		if (j <= i)
+			emulated_msrs[j] = emulated_msrs_all[i];
  		j++;
  	}
  	num_emulated_msrs = j;
- for (i = j = 0; i < ARRAY_SIZE(msr_based_features); i++) {
+	for (i = j = 0; i < ARRAY_SIZE(msr_based_features_all); i++) {
  		struct kvm_msr_entry msr;
- msr.index = msr_based_features[i];
+		msr.index = msr_based_features_all[i];
  		if (kvm_get_msr_feature(&msr))
  			continue;
- if (j < i)
-			msr_based_features[j] = msr_based_features[i];
+		if (j <= i)
+			msr_based_features[j] = msr_based_features_all[i];
  		j++;
  	}
  	num_msr_based_features = j;




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