From 9e46f6c6c959d9bb45445c2e8f04a75324a0dfd0 Mon Sep 17 00:00:00 2001 From: Babu Moger Date: Tue, 2 Mar 2021 12:51:31 -0600 Subject: KVM: SVM: Clear the CR4 register on reset 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 Message-Id: <161471109108.30811.6392805173629704166.stgit@bmoger-ubuntu> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/svm.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index c636021b066b..baee91c1e936 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1200,6 +1200,7 @@ 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); -- cgit v1.2.3