[PATCH v10 09/10] x86: spp: Add SPP protection check in emulation

Yang Weijiang
2019-12-31T06:47:16Z

In instruction/mmio emulation cases, if the target write memroy
is SPP protected, exit to user-space to handle it as if it's
caused by SPP induced EPT violation due to guest write.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 439aca0223b2..63778cd87465 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5731,6 +5731,37 @@ static const struct read_write_emulator_ops write_emultor = {
.write = true,
};

+static bool is_emulator_spp_protected(struct kvm_vcpu *vcpu,
+ gpa_t gpa,
+ unsigned int bytes)
+{
+ gfn_t gfn, start_gfn, end_gfn;
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_memory_slot *slot;
+ u32 *access;
+
+ if (!kvm->arch.spp_active)
+ return false;
+
+ start_gfn = gpa >> PAGE_SHIFT;
+ end_gfn = (gpa + bytes) >> PAGE_SHIFT;
+ for (gfn = start_gfn; gfn <= end_gfn; gfn++) {
+ slot = gfn_to_memslot(kvm, gfn);
+ if (slot) {
+ access = gfn_to_subpage_wp_info(slot, gfn);
+ if (access && *access != FULL_SPP_ACCESS) {
+ vcpu->run->exit_reason = KVM_EXIT_SPP;
+ vcpu->run->spp.addr = gfn;
+ vcpu->run->spp.ins_len =
+ kvm_x86_ops->get_inst_len(vcpu);
+ return true;
+ }
+ }
+ }
+
+ return false;
+}
+
static int emulator_read_write_onepage(unsigned long addr, void *val,
unsigned int bytes,
struct x86_exception *exception,
@@ -5761,6 +5792,9 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
return X86EMUL_PROPAGATE_FAULT;
}

+ if (write && is_emulator_spp_protected(vcpu, gpa, bytes))
+ return X86EMUL_UNHANDLEABLE;
+
if (!ret && ops->read_write_emulate(vcpu, gpa, val, bytes))
return X86EMUL_CONTINUE;

@@ -6837,6 +6871,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
return 1;

if (r == EMULATION_FAILED) {
+ if (vcpu->run->exit_reason == KVM_EXIT_SPP)
+ return 0;
+
if (reexecute_instruction(vcpu, cr2, write_fault_to_spt,
emulation_type))
return 1;
--
2.17.2