Allow userspace to set CR0, CR4, CR8, and EFER via KVM_SET_SREGS for
protected guests, e.g. for SEV-ES guests with an encrypted VMSA. KVM
tracks the aforementioned registers by trapping guest writes, and also
exposes the values to userspace via KVM_GET_SREGS. Skipping the regs
in KVM_SET_SREGS prevents userspace from updating KVM's CPU model to
match the known hardware state.
Fixes: 5265713a0737 ("KVM: x86: Update __get_sregs() / __set_sregs() to support SEV-ES")
Reported-by: Peter Gonda <pgonda@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 73 ++++++++++++++++++++++++++--------------------
1 file changed, 42 insertions(+), 31 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3bf52ba5f2bb..1b7d0e97c82b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9963,21 +9963,25 @@ static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs)
if (kvm_set_apic_base(vcpu, &apic_base_msr))
goto out;
- if (vcpu->arch.guest_state_protected)
- goto skip_protected_regs;
+ if (!vcpu->arch.guest_state_protected) {
+ dt.size = sregs->idt.limit;
+ dt.address = sregs->idt.base;
+ static_call(kvm_x86_set_idt)(vcpu, &dt);
+ dt.size = sregs->gdt.limit;
+ dt.address = sregs->gdt.base;
+ static_call(kvm_x86_set_gdt)(vcpu, &dt);
- dt.size = sregs->idt.limit;
- dt.address = sregs->idt.base;
- static_call(kvm_x86_set_idt)(vcpu, &dt);
- dt.size = sregs->gdt.limit;
- dt.address = sregs->gdt.base;
- static_call(kvm_x86_set_gdt)(vcpu, &dt);
-
- vcpu->arch.cr2 = sregs->cr2;
- mmu_reset_needed |= kvm_read_cr3(vcpu) != sregs->cr3;
- vcpu->arch.cr3 = sregs->cr3;
- kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
+ vcpu->arch.cr2 = sregs->cr2;
+ mmu_reset_needed |= kvm_read_cr3(vcpu) != sregs->cr3;
+ vcpu->arch.cr3 = sregs->cr3;
+ kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
+ }
+ /*
+ * Writes to CR0, CR4, CR8, and EFER are trapped (after the instruction
+ * completes) for SEV-EV guests, thus userspace is allowed to set them
+ * so that KVM's model can be updated to mirror hardware state.
+ */
kvm_set_cr8(vcpu, sregs->cr8);
mmu_reset_needed |= vcpu->arch.efer != sregs->efer;
@@ -9990,35 +9994,42 @@ static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs)
mmu_reset_needed |= kvm_read_cr4(vcpu) != sregs->cr4;
static_call(kvm_x86_set_cr4)(vcpu, sregs->cr4);
- idx = srcu_read_lock(&vcpu->kvm->srcu);
- if (is_pae_paging(vcpu)) {
+ /*
+ * PDPTEs, like regular PTEs, are always encrypted, thus reading them
+ * will return garbage. Shadow paging, including nested NPT, isn't
+ * compatible with protected guests, so ignoring the PDPTEs is a-ok.
+ */
+ if (!vcpu->arch.guest_state_protected && is_pae_paging(vcpu)) {
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
load_pdptrs(vcpu, vcpu->arch.walk_mmu, kvm_read_cr3(vcpu));
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
+
mmu_reset_needed = 1;
}
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
if (mmu_reset_needed)
kvm_mmu_reset_context(vcpu);
- kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS);
- kvm_set_segment(vcpu, &sregs->ds, VCPU_SREG_DS);
- kvm_set_segment(vcpu, &sregs->es, VCPU_SREG_ES);
- kvm_set_segment(vcpu, &sregs->fs, VCPU_SREG_FS);
- kvm_set_segment(vcpu, &sregs->gs, VCPU_SREG_GS);
- kvm_set_segment(vcpu, &sregs->ss, VCPU_SREG_SS);
+ if (!vcpu->arch.guest_state_protected) {
+ kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS);
+ kvm_set_segment(vcpu, &sregs->ds, VCPU_SREG_DS);
+ kvm_set_segment(vcpu, &sregs->es, VCPU_SREG_ES);
+ kvm_set_segment(vcpu, &sregs->fs, VCPU_SREG_FS);
+ kvm_set_segment(vcpu, &sregs->gs, VCPU_SREG_GS);
+ kvm_set_segment(vcpu, &sregs->ss, VCPU_SREG_SS);
- kvm_set_segment(vcpu, &sregs->tr, VCPU_SREG_TR);
- kvm_set_segment(vcpu, &sregs->ldt, VCPU_SREG_LDTR);
+ kvm_set_segment(vcpu, &sregs->tr, VCPU_SREG_TR);
+ kvm_set_segment(vcpu, &sregs->ldt, VCPU_SREG_LDTR);
- update_cr8_intercept(vcpu);
+ update_cr8_intercept(vcpu);
- /* Older userspace won't unhalt the vcpu on reset. */
- if (kvm_vcpu_is_bsp(vcpu) && kvm_rip_read(vcpu) == 0xfff0 &&
- sregs->cs.selector == 0xf000 && sregs->cs.base == 0xffff0000 &&
- !is_protmode(vcpu))
- vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ /* Older userspace won't unhalt the vcpu on reset. */
+ if (kvm_vcpu_is_bsp(vcpu) && kvm_rip_read(vcpu) == 0xfff0 &&
+ sregs->cs.selector == 0xf000 &&
+ sregs->cs.base == 0xffff0000 && !is_protmode(vcpu))
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ }
-skip_protected_regs:
max_bits = KVM_NR_INTERRUPTS;
pending_vec = find_first_bit(
(const unsigned long *)sregs->interrupt_bitmap, max_bits);
--
2.31.1.607.g51e8a6a459-goog
