Sorry for my oversight, I am adding the maintainers who were missed in the previous email. On 6/24/24 05:58, EwanHai wrote:
Commit 4a910e1 ("target/i386: do not set unsupported VMX secondary execution controls") implemented a workaround for hosts that have specific CPUID features but do not support the corresponding VMX controls, e.g., hosts support RDSEED but do not support RDSEED-Exiting. In detail, commit 4a910e1 introduced a flag `has_msr_vmx_procbased_clts2`. If KVM has `MSR_IA32_VMX_PROCBASED_CTLS2` in its msr list, QEMU would use KVM's settings, avoiding any modifications to this MSR. However, this commit (4a910e1) didn't account for cases in older Linux kernels(4.17~5.2) where `MSR_IA32_VMX_PROCBASED_CTLS2` is in `kvm_feature_msrs`-obtained by ioctl(KVM_GET_MSR_FEATURE_INDEX_LIST), but not in `kvm_msr_list`-obtained by ioctl(KVM_GET_MSR_INDEX_LIST). As a result,it did not set the `has_msr_vmx_procbased_clts2` flag based on `kvm_msr_list` alone, even though KVM does maintain the value of this MSR. This patch supplements the above logic, ensuring that `has_msr_vmx_procbased_clts2` is correctly set by checking both MSR lists, thus maintaining compatibility with older kernels. Signed-off-by: EwanHai <ewanhai-oc@xxxxxxxxxxx> --- Changes in v3: - Use a more precise version range in the comment, specifically "4.17~5.2" instead of "<5.3". Changes in v2: - Adjusted some punctuation in the commit message as per suggestions. - Added comments to the newly added code to indicate that it is a compatibility fix. v1 link: https://lore.kernel.org/all/20230925071453.14908-1-ewanhai-oc@xxxxxxxxxxx/ v2 link: https://lore.kernel.org/all/20231127034326.257596-1-ewanhai-oc@xxxxxxxxxxx/ --- target/i386/kvm/kvm.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 7ad8072748..a7c6c5b2d0 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -2386,6 +2386,7 @@ void kvm_arch_do_init_vcpu(X86CPU *cpu) static int kvm_get_supported_feature_msrs(KVMState *s) { int ret = 0; + int i;if (kvm_feature_msrs != NULL) {return 0; @@ -2420,6 +2421,20 @@ static int kvm_get_supported_feature_msrs(KVMState *s) return ret; }+ /*+ * Compatibility fix: + * Older Linux kernels (4.17~5.2) report MSR_IA32_VMX_PROCBASED_CTLS2 + * in KVM_GET_MSR_FEATURE_INDEX_LIST but not in KVM_GET_MSR_INDEX_LIST. + * This leads to an issue in older kernel versions where QEMU, + * through the KVM_GET_MSR_INDEX_LIST check, assumes the kernel + * doesn't maintain MSR_IA32_VMX_PROCBASED_CTLS2, resulting in + * incorrect settings by QEMU for this MSR. + */ + for (i = 0; i < kvm_feature_msrs->nmsrs; i++) { + if (kvm_feature_msrs->indices[i] == MSR_IA32_VMX_PROCBASED_CTLS2) { + has_msr_vmx_procbased_ctls2 = true; + } + } return 0; }
