It's not allowed to fire duplicate notification for same GFN on
x86 platform, with help of a hash table. This mechanism is going
to be used by arm64 and this makes the code generic and shareable
by multiple platforms.
* As this mechanism isn't needed by all platforms, a new kernel
config option (CONFIG_ASYNC_PF_SLOT) is introduced so that it
can be disabled at compiling time.
* The code is basically copied from x86 platform and the functions
are renamed to reflect the fact: (a) the input parameters are
vCPU and GFN. (b) The operations are resetting, searching, adding
and removing.
* Helper stub is also added on !CONFIG_KVM_ASYNC_PF because we're
going to use IS_ENABLED() instead of #ifdef on arm64 when the
asynchronous page fault is supported.
This is preparatory work to use the newly introduced functions on x86
platform and arm64 in subsequent patches.
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
include/linux/kvm_host.h | 18 +++++++++
virt/kvm/Kconfig | 3 ++
virt/kvm/async_pf.c | 85 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 106 insertions(+)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a5f990f6dc35..a9685c2b2250 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -298,6 +298,9 @@ struct kvm_vcpu {
#ifdef CONFIG_KVM_ASYNC_PF
struct {
+#ifdef CONFIG_KVM_ASYNC_PF_SLOT
+ gfn_t gfns[ASYNC_PF_PER_VCPU];
+#endif
u32 queued;
struct list_head queue;
struct list_head done;
@@ -339,6 +342,13 @@ struct kvm_async_pf {
bool notpresent_injected;
};
+#ifdef CONFIG_KVM_ASYNC_PF_SLOT
+void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu);
+void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn);
+void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn);
+bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn);
+#endif
+
static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
{
return !list_empty_careful(&vcpu->async_pf.done);
@@ -350,6 +360,14 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
unsigned long hva, struct kvm_arch_async_pf *arch);
int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
#else
+static inline void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu) { }
+static inline void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn) { }
+static inline void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn) { }
+static inline bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ return false;
+}
+
static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
{
return false;
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 62b39149b8c8..59b518c8c205 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -23,6 +23,9 @@ config KVM_MMIO
config KVM_ASYNC_PF
bool
+config KVM_ASYNC_PF_SLOT
+ bool
+
# Toggle to switch between direct notification and batch job
config KVM_ASYNC_PF_SYNC
bool
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index d145a61a046a..0d1fdb2932af 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -13,12 +13,97 @@
#include <linux/module.h>
#include <linux/mmu_context.h>
#include <linux/sched/mm.h>
+#ifdef CONFIG_KVM_ASYNC_PF_SLOT
+#include <linux/hash.h>
+#endif
#include "async_pf.h"
#include <trace/events/kvm.h>
static struct kmem_cache *async_pf_cache;
+#ifdef CONFIG_KVM_ASYNC_PF_SLOT
+static inline u32 kvm_async_pf_hash(gfn_t gfn)
+{
+ BUILD_BUG_ON(!is_power_of_2(ASYNC_PF_PER_VCPU));
+
+ return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU));
+}
+
+static inline u32 kvm_async_pf_next_slot(u32 key)
+{
+ return (key + 1) & (ASYNC_PF_PER_VCPU - 1);
+}
+
+static u32 kvm_async_pf_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ u32 key = kvm_async_pf_hash(gfn);
+ int i;
+
+ for (i = 0; i < ASYNC_PF_PER_VCPU &&
+ (vcpu->async_pf.gfns[key] != gfn &&
+ vcpu->async_pf.gfns[key] != ~0); i++)
+ key = kvm_async_pf_next_slot(key);
+
+ return key;
+}
+
+void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu)
+{
+ int i;
+
+ for (i = 0; i < ASYNC_PF_PER_VCPU; i++)
+ vcpu->async_pf.gfns[i] = ~0;
+}
+
+void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ u32 key = kvm_async_pf_hash(gfn);
+
+ while (vcpu->async_pf.gfns[key] != ~0)
+ key = kvm_async_pf_next_slot(key);
+
+ vcpu->async_pf.gfns[key] = gfn;
+}
+
+void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ u32 i, j, k;
+
+ i = j = kvm_async_pf_slot(vcpu, gfn);
+
+ if (WARN_ON_ONCE(vcpu->async_pf.gfns[i] != gfn))
+ return;
+
+ while (true) {
+ vcpu->async_pf.gfns[i] = ~0;
+
+ do {
+ j = kvm_async_pf_next_slot(j);
+ if (vcpu->async_pf.gfns[j] == ~0)
+ return;
+
+ k = kvm_async_pf_hash(vcpu->async_pf.gfns[j]);
+ /*
+ * k lies cyclically in ]i,j]
+ * | i.k.j |
+ * |....j i.k.| or |.k..j i...|
+ */
+ } while ((i <= j) ? (i < k && k <= j) : (i < k || k <= j));
+
+ vcpu->async_pf.gfns[i] = vcpu->async_pf.gfns[j];
+ i = j;
+ }
+}
+
+bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ u32 key = kvm_async_pf_slot(vcpu, gfn);
+
+ return vcpu->async_pf.gfns[key] == gfn;
+}
+#endif /* CONFIG_KVM_ASYNC_PF_SLOT */
+
int kvm_async_pf_init(void)
{
async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
--
2.23.0
