[PATCH 5.14 42/48] KVM: x86: reset pdptrs_from_userspace when exiting smm

Greg Kroah-Hartman
2021-10-08T11:39:21Z

From: Maxim Levitsky <mlevitsk@redhat.com>

[ Upstream commit 37687c403a641f251cb2ef2e7830b88aa0647ba9 ]

When exiting SMM, pdpts are loaded again from the guest memory.

This fixes a theoretical bug, when exit from SMM triggers entry to the
nested guest which re-uses some of the migration
code which uses this flag as a workaround for a legacy userspace.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210913140954.165665-4-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/x86.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6d5d6e93f5c4..07d3d8aa50a9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7659,6 +7659,13 @@ static void kvm_smm_changed(struct kvm_vcpu *vcpu, bool entering_smm)

/* Process a latched INIT or SMI, if any. */
kvm_make_request(KVM_REQ_EVENT, vcpu);
+
+ /*
+ * Even if KVM_SET_SREGS2 loaded PDPTRs out of band,
+ * on SMM exit we still need to reload them from
+ * guest memory
+ */
+ vcpu->arch.pdptrs_from_userspace = false;
}

kvm_mmu_reset_context(vcpu);
--
2.33.0