From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+fb0b6a7e8713aeb0319c@syzkaller.appspotmail.com
Subject: [PATCH 5/9] KVM: x86: Move (most) SMM hflags modifications into kvm_smm_changed()
Date: Wed, 9 Jun 2021 11:56:15 -0700 [thread overview]
Message-ID: <20210609185619.992058-6-seanjc@google.com> (raw)
In-Reply-To: <20210609185619.992058-1-seanjc@google.com>
Move the core of SMM hflags modifications into kvm_smm_changed() and use
kvm_smm_changed() in enter_smm(). Clear HF_SMM_INSIDE_NMI_MASK for
leaving SMM but do not set it for entering SMM. If the vCPU is executing
outside of SMM, the flag should unequivocally be cleared, e.g. this
technically fixes a benign bug where the flag could be left set after
KVM_SET_VCPU_EVENTS, but the reverse is not true as NMI blocking depends
on pre-SMM state or userspace input.
Note, this adds an extra kvm_mmu_reset_context() to enter_smm(). The
extra/early reset isn't strictly necessary, and in a way can never be
necessary since the vCPU/MMU context is in a half-baked state until the
final context reset at the end of the function. But, enter_smm() is not
a hot path, and exploding on an invalid root_hpa is probably better than
having a stale SMM flag in the MMU role; it's at least no worse.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 76ba28865824..13a33c962657 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4457,7 +4457,7 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
memset(&events->reserved, 0, sizeof(events->reserved));
}
-static void kvm_smm_changed(struct kvm_vcpu *vcpu);
+static void kvm_smm_changed(struct kvm_vcpu *vcpu, bool entering_smm);
static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
struct kvm_vcpu_events *events)
@@ -4517,13 +4517,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
vcpu->arch.apic->sipi_vector = events->sipi_vector;
if (events->flags & KVM_VCPUEVENT_VALID_SMM) {
- if (!!(vcpu->arch.hflags & HF_SMM_MASK) != events->smi.smm) {
- if (events->smi.smm)
- vcpu->arch.hflags |= HF_SMM_MASK;
- else
- vcpu->arch.hflags &= ~HF_SMM_MASK;
- kvm_smm_changed(vcpu);
- }
+ if (!!(vcpu->arch.hflags & HF_SMM_MASK) != events->smi.smm)
+ kvm_smm_changed(vcpu, events->smi.smm);
vcpu->arch.smi_pending = events->smi.pending;
@@ -7108,8 +7103,7 @@ static void emulator_exiting_smm(struct x86_emulate_ctxt *ctxt)
{
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
- vcpu->arch.hflags &= ~(HF_SMM_MASK | HF_SMM_INSIDE_NMI_MASK);
- kvm_smm_changed(vcpu);
+ kvm_smm_changed(vcpu, false);
}
static int emulator_pre_leave_smm(struct x86_emulate_ctxt *ctxt,
@@ -7438,9 +7432,13 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
static int complete_emulated_mmio(struct kvm_vcpu *vcpu);
static int complete_emulated_pio(struct kvm_vcpu *vcpu);
-static void kvm_smm_changed(struct kvm_vcpu *vcpu)
+static void kvm_smm_changed(struct kvm_vcpu *vcpu, bool entering_smm)
{
- if (!(vcpu->arch.hflags & HF_SMM_MASK)) {
+ if (entering_smm) {
+ vcpu->arch.hflags |= HF_SMM_MASK;
+ } else {
+ vcpu->arch.hflags &= ~(HF_SMM_MASK | HF_SMM_INSIDE_NMI_MASK);
+
/* This is a good place to trace that we are exiting SMM. */
trace_kvm_enter_smm(vcpu->vcpu_id, vcpu->arch.smbase, false);
@@ -8912,7 +8910,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
*/
static_call(kvm_x86_pre_enter_smm)(vcpu, buf);
- vcpu->arch.hflags |= HF_SMM_MASK;
+ kvm_smm_changed(vcpu, true);
kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, buf, sizeof(buf));
if (static_call(kvm_x86_get_nmi_mask)(vcpu))
--
2.32.0.rc1.229.g3e70b5a671-goog
next prev parent reply other threads:[~2021-06-09 18:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 18:56 [PATCH 0/9] KVM: x86: Fix NULL pointer #GP due to RSM bug Sean Christopherson
2021-06-09 18:56 ` [PATCH 1/9] KVM: x86: Immediately reset the MMU context when the SMM flag is cleared Sean Christopherson
2021-06-10 13:19 ` Paolo Bonzini
2021-06-09 18:56 ` [PATCH 2/9] KVM: x86: Emulate triple fault shutdown if RSM emulation fails Sean Christopherson
2021-06-10 8:26 ` Vitaly Kuznetsov
2021-06-10 13:29 ` Paolo Bonzini
2021-06-10 15:28 ` Sean Christopherson
2021-06-10 15:30 ` Sean Christopherson
2021-06-11 11:42 ` Vitaly Kuznetsov
2021-06-10 13:23 ` Paolo Bonzini
2021-06-09 18:56 ` [PATCH 3/9] KVM: x86: Replace .set_hflags() with dedicated .exiting_smm() helper Sean Christopherson
2021-06-09 18:56 ` [PATCH 4/9] KVM: x86: Invoke kvm_smm_changed() immediately after clearing SMM flag Sean Christopherson
2021-06-09 18:56 ` Sean Christopherson [this message]
2021-06-09 18:56 ` [PATCH 6/9] KVM: x86: Move "entering SMM" tracepoint into kvm_smm_changed() Sean Christopherson
2021-06-09 18:56 ` [PATCH 7/9] KVM: x86: Rename SMM tracepoint to make it reflect reality Sean Christopherson
2021-06-09 18:56 ` [PATCH 8/9] KVM: x86: Drop .post_leave_smm(), i.e. the manual post-RSM MMU reset Sean Christopherson
2021-06-09 18:56 ` [PATCH 9/9] KVM: x86: Drop "pre_" from enter/leave_smm() helpers Sean Christopherson
2021-06-10 13:28 ` [PATCH 0/9] KVM: x86: Fix NULL pointer #GP due to RSM bug Paolo Bonzini
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