Joel Schopp <joel.schopp@xxxxxxx> writes:
> There isn't really a valid reason for kvm to intercept cr* reads
> on svm hardware. The current kvm code just ends up returning
> the register
>
> Signed-off-by: Joel Schopp <joel.schopp@xxxxxxx>
> ---
> arch/x86/kvm/svm.c | 41 ++++-------------------------------------
> 1 file changed, 4 insertions(+), 37 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index cc618c8..c3d10e6 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1090,9 +1090,6 @@ static void init_vmcb(struct vcpu_svm *svm)
> svm->vcpu.fpu_active = 1;
> svm->vcpu.arch.hflags = 0;
>
> - set_cr_intercept(svm, INTERCEPT_CR0_READ);
> - set_cr_intercept(svm, INTERCEPT_CR3_READ);
> - set_cr_intercept(svm, INTERCEPT_CR4_READ);
> set_cr_intercept(svm, INTERCEPT_CR0_WRITE);
> set_cr_intercept(svm, INTERCEPT_CR3_WRITE);
> set_cr_intercept(svm, INTERCEPT_CR4_WRITE);
> @@ -1174,7 +1171,6 @@ static void init_vmcb(struct vcpu_svm *svm)
> control->nested_ctl = 1;
> clr_intercept(svm, INTERCEPT_INVLPG);
> clr_exception_intercept(svm, PF_VECTOR);
> - clr_cr_intercept(svm, INTERCEPT_CR3_READ);
> clr_cr_intercept(svm, INTERCEPT_CR3_WRITE);
> save->g_pat = 0x0007040600070406ULL;
> save->cr3 = 0;
> @@ -2968,29 +2964,10 @@ static int cr_interception(struct vcpu_svm *svm)
> kvm_queue_exception(&svm->vcpu, UD_VECTOR);
> return 1;
> }
> - } else { /* mov from cr */
> - switch (cr) {
> - case 0:
> - val = kvm_read_cr0(&svm->vcpu);
> - break;
> - case 2:
> - val = svm->vcpu.arch.cr2;
> - break;
> - case 3:
> - val = kvm_read_cr3(&svm->vcpu);
> - break;
> - case 4:
> - val = kvm_read_cr4(&svm->vcpu);
> - break;
> - case 8:
> - val = kvm_get_cr8(&svm->vcpu);
> - break;
> - default:
> - WARN(1, "unhandled read from CR%d", cr);
> - kvm_queue_exception(&svm->vcpu, UD_VECTOR);
> - return 1;
> - }
> - kvm_register_write(&svm->vcpu, reg, val);
> + } else { /* mov from cr, should never trap in svm */
> + WARN(1, "unhandled read from CR%d", cr);
> + kvm_queue_exception(&svm->vcpu, UD_VECTOR);
> + return 1;
Can we end up here if a nested hypervisor sets cr read interception ?
Bandan
> }
> kvm_complete_insn_gp(&svm->vcpu, err);
>
> @@ -3321,10 +3298,6 @@ static int mwait_interception(struct vcpu_svm *svm)
> }
>
> static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
> - [SVM_EXIT_READ_CR0] = cr_interception,
> - [SVM_EXIT_READ_CR3] = cr_interception,
> - [SVM_EXIT_READ_CR4] = cr_interception,
> - [SVM_EXIT_READ_CR8] = cr_interception,
> [SVM_EXIT_CR0_SEL_WRITE] = emulate_on_interception,
> [SVM_EXIT_WRITE_CR0] = cr_interception,
> [SVM_EXIT_WRITE_CR3] = cr_interception,
> @@ -4151,11 +4124,9 @@ static const struct __x86_intercept {
> u32 exit_code;
> enum x86_intercept_stage stage;
> } x86_intercept_map[] = {
> - [x86_intercept_cr_read] = POST_EX(SVM_EXIT_READ_CR0),
> [x86_intercept_cr_write] = POST_EX(SVM_EXIT_WRITE_CR0),
> [x86_intercept_clts] = POST_EX(SVM_EXIT_WRITE_CR0),
> [x86_intercept_lmsw] = POST_EX(SVM_EXIT_WRITE_CR0),
> - [x86_intercept_smsw] = POST_EX(SVM_EXIT_READ_CR0),
> [x86_intercept_dr_read] = POST_EX(SVM_EXIT_READ_DR0),
> [x86_intercept_dr_write] = POST_EX(SVM_EXIT_WRITE_DR0),
> [x86_intercept_sldt] = POST_EX(SVM_EXIT_LDTR_READ),
> @@ -4221,10 +4192,6 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
> goto out;
>
> switch (icpt_info.exit_code) {
> - case SVM_EXIT_READ_CR0:
> - if (info->intercept == x86_intercept_cr_read)
> - icpt_info.exit_code += info->modrm_reg;
> - break;
> case SVM_EXIT_WRITE_CR0: {
> unsigned long cr0, val;
> u64 intercept;
>
> --
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