[PATCH 01/16] KVM: Initialize gfn_to_pfn_cache locks in dedicated helper

From: Paolo Bonzini
Date: Thu Oct 27 2022 - 12:21:04 EST

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Previous message: Paolo Bonzini: "[PATCH 16/16] KVM: selftests: Mark "guest_saw_irq" as volatile in xen_shinfo_test"
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From: Michal Luczaj <mhal@xxxxxxx>

Move the gfn_to_pfn_cache lock initialization to another helper and
call the new helper during VM/vCPU creation. There are race
conditions possible due to kvm_gfn_to_pfn_cache_init()'s
ability to re-initialize the cache's locks.

For example: a race between ioctl(KVM_XEN_HVM_EVTCHN_SEND) and
kvm_gfn_to_pfn_cache_init() leads to a corrupted shinfo gpc lock.

(thread 1) | (thread 2)
|
kvm_xen_set_evtchn_fast |
read_lock_irqsave(&gpc->lock, ...) |
| kvm_gfn_to_pfn_cache_init
| rwlock_init(&gpc->lock)
read_unlock_irqrestore(&gpc->lock, ...) |

Rename "cache_init" and "cache_destroy" to activate+deactivate to
avoid implying that the cache really is destroyed/freed.

Note, there more races in the newly named kvm_gpc_activate() that will
be addressed separately.

Fixes: 982ed0de4753 ("KVM: Reinstate gfn_to_pfn_cache with invalidation support")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
[sean: call out that this is a bug fix]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20221013211234.1318131-2-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 12 +++++----
arch/x86/kvm/xen.c | 57 +++++++++++++++++++++-------------------
include/linux/kvm_host.h | 24 ++++++++++++-----
virt/kvm/pfncache.c | 21 ++++++++-------
4 files changed, 66 insertions(+), 48 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 104b72df33d6..521b433f978c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2315,11 +2315,11 @@ static void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time,

/* we verify if the enable bit is set... */
if (system_time & 1) {
- kvm_gfn_to_pfn_cache_init(vcpu->kvm, &vcpu->arch.pv_time, vcpu,
- KVM_HOST_USES_PFN, system_time & ~1ULL,
- sizeof(struct pvclock_vcpu_time_info));
+ kvm_gpc_activate(vcpu->kvm, &vcpu->arch.pv_time, vcpu,
+ KVM_HOST_USES_PFN, system_time & ~1ULL,
+ sizeof(struct pvclock_vcpu_time_info));
} else {
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm, &vcpu->arch.pv_time);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.pv_time);
}

return;
@@ -3388,7 +3388,7 @@ static int kvm_pv_enable_async_pf_int(struct kvm_vcpu *vcpu, u64 data)

static void kvmclock_reset(struct kvm_vcpu *vcpu)
{
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm, &vcpu->arch.pv_time);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.pv_time);
vcpu->arch.time = 0;
}

@@ -11829,6 +11829,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.regs_avail = ~0;
vcpu->arch.regs_dirty = ~0;

+ kvm_gpc_init(&vcpu->arch.pv_time);
+
if (!irqchip_in_kernel(vcpu->kvm) || kvm_vcpu_is_reset_bsp(vcpu))
vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
else
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 93c628d3e3a9..b2be60c6efa4 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -42,13 +42,13 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
int idx = srcu_read_lock(&kvm->srcu);

if (gfn == GPA_INVALID) {
- kvm_gfn_to_pfn_cache_destroy(kvm, gpc);
+ kvm_gpc_deactivate(kvm, gpc);
goto out;
}

do {
- ret = kvm_gfn_to_pfn_cache_init(kvm, gpc, NULL, KVM_HOST_USES_PFN,
- gpa, PAGE_SIZE);
+ ret = kvm_gpc_activate(kvm, gpc, NULL, KVM_HOST_USES_PFN, gpa,
+ PAGE_SIZE);
if (ret)
goto out;

@@ -554,15 +554,15 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
offsetof(struct compat_vcpu_info, time));

if (data->u.gpa == GPA_INVALID) {
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm, &vcpu->arch.xen.vcpu_info_cache);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_info_cache);
r = 0;
break;
}

- r = kvm_gfn_to_pfn_cache_init(vcpu->kvm,
- &vcpu->arch.xen.vcpu_info_cache,
- NULL, KVM_HOST_USES_PFN, data->u.gpa,
- sizeof(struct vcpu_info));
+ r = kvm_gpc_activate(vcpu->kvm,
+ &vcpu->arch.xen.vcpu_info_cache, NULL,
+ KVM_HOST_USES_PFN, data->u.gpa,
+ sizeof(struct vcpu_info));
if (!r)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

@@ -570,16 +570,16 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)

case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
if (data->u.gpa == GPA_INVALID) {
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
- &vcpu->arch.xen.vcpu_time_info_cache);
+ kvm_gpc_deactivate(vcpu->kvm,
+ &vcpu->arch.xen.vcpu_time_info_cache);
r = 0;
break;
}

- r = kvm_gfn_to_pfn_cache_init(vcpu->kvm,
- &vcpu->arch.xen.vcpu_time_info_cache,
- NULL, KVM_HOST_USES_PFN, data->u.gpa,
- sizeof(struct pvclock_vcpu_time_info));
+ r = kvm_gpc_activate(vcpu->kvm,
+ &vcpu->arch.xen.vcpu_time_info_cache,
+ NULL, KVM_HOST_USES_PFN, data->u.gpa,
+ sizeof(struct pvclock_vcpu_time_info));
if (!r)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
break;
@@ -590,16 +590,15 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
break;
}
if (data->u.gpa == GPA_INVALID) {
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
- &vcpu->arch.xen.runstate_cache);
+ kvm_gpc_deactivate(vcpu->kvm,
+ &vcpu->arch.xen.runstate_cache);
r = 0;
break;
}

- r = kvm_gfn_to_pfn_cache_init(vcpu->kvm,
- &vcpu->arch.xen.runstate_cache,
- NULL, KVM_HOST_USES_PFN, data->u.gpa,
- sizeof(struct vcpu_runstate_info));
+ r = kvm_gpc_activate(vcpu->kvm, &vcpu->arch.xen.runstate_cache,
+ NULL, KVM_HOST_USES_PFN, data->u.gpa,
+ sizeof(struct vcpu_runstate_info));
break;

case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
@@ -1816,7 +1815,12 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
{
vcpu->arch.xen.vcpu_id = vcpu->vcpu_idx;
vcpu->arch.xen.poll_evtchn = 0;
+
timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
+
+ kvm_gpc_init(&vcpu->arch.xen.runstate_cache);
+ kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache);
+ kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache);
}

void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
@@ -1824,18 +1828,17 @@ void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu)
if (kvm_xen_timer_enabled(vcpu))
kvm_xen_stop_timer(vcpu);

- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
- &vcpu->arch.xen.runstate_cache);
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
- &vcpu->arch.xen.vcpu_info_cache);
- kvm_gfn_to_pfn_cache_destroy(vcpu->kvm,
- &vcpu->arch.xen.vcpu_time_info_cache);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.runstate_cache);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_info_cache);
+ kvm_gpc_deactivate(vcpu->kvm, &vcpu->arch.xen.vcpu_time_info_cache);
+
del_timer_sync(&vcpu->arch.xen.poll_timer);
}

void kvm_xen_init_vm(struct kvm *kvm)
{
idr_init(&kvm->arch.xen.evtchn_ports);
+ kvm_gpc_init(&kvm->arch.xen.shinfo_cache);
}

void kvm_xen_destroy_vm(struct kvm *kvm)
@@ -1843,7 +1846,7 @@ void kvm_xen_destroy_vm(struct kvm *kvm)
struct evtchnfd *evtchnfd;
int i;

- kvm_gfn_to_pfn_cache_destroy(kvm, &kvm->arch.xen.shinfo_cache);
+ kvm_gpc_deactivate(kvm, &kvm->arch.xen.shinfo_cache);

idr_for_each_entry(&kvm->arch.xen.evtchn_ports, evtchnfd, i) {
if (!evtchnfd->deliver.port.port)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 00c3448ba7f8..18592bdf4c1b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1240,8 +1240,18 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data,
void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);

/**
- * kvm_gfn_to_pfn_cache_init - prepare a cached kernel mapping and HPA for a
- * given guest physical address.
+ * kvm_gpc_init - initialize gfn_to_pfn_cache.
+ *
+ * @gpc: struct gfn_to_pfn_cache object.
+ *
+ * This sets up a gfn_to_pfn_cache by initializing locks. Note, the cache must
+ * be zero-allocated (or zeroed by the caller before init).
+ */
+void kvm_gpc_init(struct gfn_to_pfn_cache *gpc);
+
+/**
+ * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest
+ * physical address.
*
* @kvm: pointer to kvm instance.
* @gpc: struct gfn_to_pfn_cache object.
@@ -1265,9 +1275,9 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn);
* kvm_gfn_to_pfn_cache_check() to ensure that the cache is valid before
* accessing the target page.
*/
-int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
- struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
- gpa_t gpa, unsigned long len);
+int kvm_gpc_activate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
+ struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
+ gpa_t gpa, unsigned long len);

/**
* kvm_gfn_to_pfn_cache_check - check validity of a gfn_to_pfn_cache.
@@ -1324,7 +1334,7 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
void kvm_gfn_to_pfn_cache_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);

/**
- * kvm_gfn_to_pfn_cache_destroy - destroy and unlink a gfn_to_pfn_cache.
+ * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.
*
* @kvm: pointer to kvm instance.
* @gpc: struct gfn_to_pfn_cache object.
@@ -1332,7 +1342,7 @@ void kvm_gfn_to_pfn_cache_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
* This removes a cache from the @kvm's list to be processed on MMU notifier
* invocation.
*/
-void kvm_gfn_to_pfn_cache_destroy(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
+void kvm_gpc_deactivate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);

void kvm_sigset_activate(struct kvm_vcpu *vcpu);
void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 68ff41d39545..08f97cf97264 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -346,17 +346,20 @@ void kvm_gfn_to_pfn_cache_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
}
EXPORT_SYMBOL_GPL(kvm_gfn_to_pfn_cache_unmap);

+void kvm_gpc_init(struct gfn_to_pfn_cache *gpc)
+{
+ rwlock_init(&gpc->lock);
+ mutex_init(&gpc->refresh_lock);
+}
+EXPORT_SYMBOL_GPL(kvm_gpc_init);

-int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
- struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
- gpa_t gpa, unsigned long len)
+int kvm_gpc_activate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
+ struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,
+ gpa_t gpa, unsigned long len)
{
WARN_ON_ONCE(!usage || (usage & KVM_GUEST_AND_HOST_USE_PFN) != usage);

if (!gpc->active) {
- rwlock_init(&gpc->lock);
- mutex_init(&gpc->refresh_lock);
-
gpc->khva = NULL;
gpc->pfn = KVM_PFN_ERR_FAULT;
gpc->uhva = KVM_HVA_ERR_BAD;
@@ -371,9 +374,9 @@ int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
}
return kvm_gfn_to_pfn_cache_refresh(kvm, gpc, gpa, len);
}
-EXPORT_SYMBOL_GPL(kvm_gfn_to_pfn_cache_init);
+EXPORT_SYMBOL_GPL(kvm_gpc_activate);

-void kvm_gfn_to_pfn_cache_destroy(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
+void kvm_gpc_deactivate(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
{
if (gpc->active) {
spin_lock(&kvm->gpc_lock);
@@ -384,4 +387,4 @@ void kvm_gfn_to_pfn_cache_destroy(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
gpc->active = false;
}
}
-EXPORT_SYMBOL_GPL(kvm_gfn_to_pfn_cache_destroy);
+EXPORT_SYMBOL_GPL(kvm_gpc_deactivate);
--
2.31.1

Next message: Darrick J. Wong: "Re: [tip:x86/core] [kallsyms] f138918162: WARNING:CPU:#PID:#at_fs/xfs/xfs_message.c:#xfs_buf_alert_ratelimited.cold-#[xfs]"
Previous message: Paolo Bonzini: "[PATCH 16/16] KVM: selftests: Mark "guest_saw_irq" as volatile in xen_shinfo_test"
In reply to: Paolo Bonzini: "[PATCH 16/16] KVM: selftests: Mark "guest_saw_irq" as volatile in xen_shinfo_test"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]