From: Babu Moger babu.moger@amd.com
mainline inclusion from mainline-v5.12-rc2 commit 9e46f6c6c959d9bb45445c2e8f04a75324a0dfd0 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I4MKP4 CVE: NA
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This problem was reported on a SVM guest while executing kexec. Kexec fails to load the new kernel when the PCID feature is enabled.
When kexec starts loading the new kernel, it starts the process by resetting the vCPU's and then bringing each vCPU online one by one. The vCPU reset is supposed to reset all the register states before the vCPUs are brought online. However, the CR4 register is not reset during this process. If this register is already setup during the last boot, all the flags can remain intact. The X86_CR4_PCIDE bit can only be enabled in long mode. So, it must be enabled much later in SMP initialization. Having the X86_CR4_PCIDE bit set during SMP boot can cause a boot failures.
Fix the issue by resetting the CR4 register in init_vmcb().
Signed-off-by: Babu Moger babu.moger@amd.com Message-Id: 161471109108.30811.6392805173629704166.stgit@bmoger-ubuntu Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Jackie Liu liuyun01@kylinos.cn Signed-off-by: Laibin Qiu qiulaibin@huawei.com --- arch/x86/kvm/svm.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 2355f20b1342..46567343680f 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -389,6 +389,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm); static int nested_svm_vmexit(struct vcpu_svm *svm); static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr, bool has_error_code, u32 error_code); +static int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
enum { VMCB_INTERCEPTS, /* Intercept vectors, TSC offset, @@ -1613,6 +1614,7 @@ static void init_vmcb(struct vcpu_svm *svm) init_sys_seg(&save->ldtr, SEG_TYPE_LDT); init_sys_seg(&save->tr, SEG_TYPE_BUSY_TSS16);
+ svm_set_cr4(&svm->vcpu, 0); svm_set_efer(&svm->vcpu, 0); save->dr6 = 0xffff0ff0; kvm_set_rflags(&svm->vcpu, X86_EFLAGS_FIXED);