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

[Paolo Bonzini <pbonzini@redhat.com>]

On 06/11/19 07:35, 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@vger.kernel.org
> Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
> ---
> 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 is always <= i, so we can remove the ifs.

>  		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;
> 

Queued, thanks.

Paolo