From: Chao Peng <chao.p.peng@linux.intel.com>
Currently in mmu_notifier invalidate path, hva range is recorded and
then checked against by mmu_notifier_retry_hva() in the page fault
handling path. However, for the to be introduced private memory, a page
fault may not have a hva associated, checking gfn(gpa) makes more sense.
For existing hva based shared memory, gfn is expected to also work. The
only downside is when aliasing multiple gfns to a single hva, the
current algorithm of checking multiple ranges could result in a much
larger range being rejected. Such aliasing should be uncommon, so the
impact is expected small.
Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
[sean: convert vmx_set_apic_access_page_addr() to gfn-based API]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/mmu.c | 10 ++++++----
arch/x86/kvm/vmx/vmx.c | 11 +++++------
include/linux/kvm_host.h | 33 ++++++++++++++++++++------------
virt/kvm/kvm_main.c | 41 +++++++++++++++++++++++++++++++---------
4 files changed, 64 insertions(+), 31 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index f7901cb4d2fa..d33657d61d80 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3056,7 +3056,7 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
*
* There are several ways to safely use this helper:
*
- * - Check mmu_invalidate_retry_hva() after grabbing the mapping level, before
+ * - Check mmu_invalidate_retry_gfn() after grabbing the mapping level, before
* consuming it. In this case, mmu_lock doesn't need to be held during the
* lookup, but it does need to be held while checking the MMU notifier.
*
@@ -4358,7 +4358,7 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
return true;
return fault->slot &&
- mmu_invalidate_retry_hva(vcpu->kvm, fault->mmu_seq, fault->hva);
+ mmu_invalidate_retry_gfn(vcpu->kvm, fault->mmu_seq, fault->gfn);
}
static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
@@ -6245,7 +6245,9 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
write_lock(&kvm->mmu_lock);
- kvm_mmu_invalidate_begin(kvm, 0, -1ul);
+ kvm_mmu_invalidate_begin(kvm);
+
+ kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end);
flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end);
@@ -6255,7 +6257,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
if (flush)
kvm_flush_remote_tlbs_range(kvm, gfn_start, gfn_end - gfn_start);
- kvm_mmu_invalidate_end(kvm, 0, -1ul);
+ kvm_mmu_invalidate_end(kvm);
write_unlock(&kvm->mmu_lock);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 72e3943f3693..6e502ba93141 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6757,10 +6757,10 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
return;
/*
- * Grab the memslot so that the hva lookup for the mmu_notifier retry
- * is guaranteed to use the same memslot as the pfn lookup, i.e. rely
- * on the pfn lookup's validation of the memslot to ensure a valid hva
- * is used for the retry check.
+ * Explicitly grab the memslot using KVM's internal slot ID to ensure
+ * KVM doesn't unintentionally grab a userspace memslot. It _should_
+ * be impossible for userspace to create a memslot for the APIC when
+ * APICv is enabled, but paranoia won't hurt in this case.
*/
slot = id_to_memslot(slots, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT);
if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
@@ -6785,8 +6785,7 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
return;
read_lock(&vcpu->kvm->mmu_lock);
- if (mmu_invalidate_retry_hva(kvm, mmu_seq,
- gfn_to_hva_memslot(slot, gfn))) {
+ if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn)) {
kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
read_unlock(&vcpu->kvm->mmu_lock);
goto out;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fb6c6109fdca..11d091688346 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -787,8 +787,8 @@ struct kvm {
struct mmu_notifier mmu_notifier;
unsigned long mmu_invalidate_seq;
long mmu_invalidate_in_progress;
- unsigned long mmu_invalidate_range_start;
- unsigned long mmu_invalidate_range_end;
+ gfn_t mmu_invalidate_range_start;
+ gfn_t mmu_invalidate_range_end;
#endif
struct list_head devices;
u64 manual_dirty_log_protect;
@@ -1392,10 +1392,9 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc);
void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
#endif
-void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
- unsigned long end);
-void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
- unsigned long end);
+void kvm_mmu_invalidate_begin(struct kvm *kvm);
+void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end);
+void kvm_mmu_invalidate_end(struct kvm *kvm);
long kvm_arch_dev_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg);
@@ -1970,9 +1969,9 @@ static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq)
return 0;
}
-static inline int mmu_invalidate_retry_hva(struct kvm *kvm,
+static inline int mmu_invalidate_retry_gfn(struct kvm *kvm,
unsigned long mmu_seq,
- unsigned long hva)
+ gfn_t gfn)
{
lockdep_assert_held(&kvm->mmu_lock);
/*
@@ -1981,10 +1980,20 @@ static inline int mmu_invalidate_retry_hva(struct kvm *kvm,
* that might be being invalidated. Note that it may include some false
* positives, due to shortcuts when handing concurrent invalidations.
*/
- if (unlikely(kvm->mmu_invalidate_in_progress) &&
- hva >= kvm->mmu_invalidate_range_start &&
- hva < kvm->mmu_invalidate_range_end)
- return 1;
+ if (unlikely(kvm->mmu_invalidate_in_progress)) {
+ /*
+ * Dropping mmu_lock after bumping mmu_invalidate_in_progress
+ * but before updating the range is a KVM bug.
+ */
+ if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA ||
+ kvm->mmu_invalidate_range_end == INVALID_GPA))
+ return 1;
+
+ if (gfn >= kvm->mmu_invalidate_range_start &&
+ gfn < kvm->mmu_invalidate_range_end)
+ return 1;
+ }
+
if (kvm->mmu_invalidate_seq != mmu_seq)
return 1;
return 0;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5a97e6c7d9c2..1a577a25de47 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -543,9 +543,7 @@ static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
typedef bool (*gfn_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range);
-typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start,
- unsigned long end);
-
+typedef void (*on_lock_fn_t)(struct kvm *kvm);
typedef void (*on_unlock_fn_t)(struct kvm *kvm);
struct kvm_mmu_notifier_range {
@@ -637,7 +635,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
locked = true;
KVM_MMU_LOCK(kvm);
if (!IS_KVM_NULL_FN(range->on_lock))
- range->on_lock(kvm, range->start, range->end);
+ range->on_lock(kvm);
+
if (IS_KVM_NULL_FN(range->handler))
break;
}
@@ -742,16 +741,29 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
kvm_handle_hva_range(mn, address, address + 1, arg, kvm_change_spte_gfn);
}
-void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
- unsigned long end)
+void kvm_mmu_invalidate_begin(struct kvm *kvm)
{
+ lockdep_assert_held_write(&kvm->mmu_lock);
/*
* The count increase must become visible at unlock time as no
* spte can be established without taking the mmu_lock and
* count is also read inside the mmu_lock critical section.
*/
kvm->mmu_invalidate_in_progress++;
+
if (likely(kvm->mmu_invalidate_in_progress == 1)) {
+ kvm->mmu_invalidate_range_start = INVALID_GPA;
+ kvm->mmu_invalidate_range_end = INVALID_GPA;
+ }
+}
+
+void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+ lockdep_assert_held_write(&kvm->mmu_lock);
+
+ WARN_ON_ONCE(!kvm->mmu_invalidate_in_progress);
+
+ if (likely(kvm->mmu_invalidate_range_start == INVALID_GPA)) {
kvm->mmu_invalidate_range_start = start;
kvm->mmu_invalidate_range_end = end;
} else {
@@ -771,6 +783,12 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
}
}
+static bool kvm_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
+{
+ kvm_mmu_invalidate_range_add(kvm, range->start, range->end);
+ return kvm_unmap_gfn_range(kvm, range);
+}
+
static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
@@ -778,7 +796,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
const struct kvm_mmu_notifier_range hva_range = {
.start = range->start,
.end = range->end,
- .handler = kvm_unmap_gfn_range,
+ .handler = kvm_mmu_unmap_gfn_range,
.on_lock = kvm_mmu_invalidate_begin,
.on_unlock = kvm_arch_guest_memory_reclaimed,
.flush_on_ret = true,
@@ -817,8 +835,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
return 0;
}
-void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
- unsigned long end)
+void kvm_mmu_invalidate_end(struct kvm *kvm)
{
/*
* This sequence increase will notify the kvm page fault that
@@ -834,6 +851,12 @@ void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
*/
kvm->mmu_invalidate_in_progress--;
KVM_BUG_ON(kvm->mmu_invalidate_in_progress < 0, kvm);
+
+ /*
+ * Assert that at least one range was added between start() and end().
+ * Not adding a range isn't fatal, but it is a KVM bug.
+ */
+ WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA);
}
static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
--
2.42.0.820.g83a721a137-googOn Fri, Oct 27, 2023 at 11:21:45AM -0700, Sean Christopherson wrote:
> From: Chao Peng <chao.p.peng@linux.intel.com>
>
> Currently in mmu_notifier invalidate path, hva range is recorded and
> then checked against by mmu_notifier_retry_hva() in the page fault
^
should be mmu_invalidate_retry_hva().
Besides this, Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Thanks
On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> From: Chao Peng <chao.p.peng@linux.intel.com>
>
> Currently in mmu_notifier invalidate path, hva range is recorded and
> then checked against by mmu_notifier_retry_hva() in the page fault
> handling path. However, for the to be introduced private memory, a page
^^^^^^^^^^^^^^^^^^^^^^^^
Is there a missing word here?
> fault may not have a hva associated, checking gfn(gpa) makes more sense.
>
> For existing hva based shared memory, gfn is expected to also work. The
> only downside is when aliasing multiple gfns to a single hva, the
> current algorithm of checking multiple ranges could result in a much
> larger range being rejected. Such aliasing should be uncommon, so the
> impact is expected small.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Cc: Xu Yilun <yilun.xu@intel.com>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> Reviewed-by: Fuad Tabba <tabba@google.com>
> Tested-by: Fuad Tabba <tabba@google.com>
> [sean: convert vmx_set_apic_access_page_addr() to gfn-based API]
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 10 ++++++----
> arch/x86/kvm/vmx/vmx.c | 11 +++++------
> include/linux/kvm_host.h | 33 ++++++++++++++++++++------------
> virt/kvm/kvm_main.c | 41 +++++++++++++++++++++++++++++++---------
> 4 files changed, 64 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index f7901cb4d2fa..d33657d61d80 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3056,7 +3056,7 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
> *
> * There are several ways to safely use this helper:
> *
> - * - Check mmu_invalidate_retry_hva() after grabbing the mapping level, before
> + * - Check mmu_invalidate_retry_gfn() after grabbing the mapping level, before
> * consuming it. In this case, mmu_lock doesn't need to be held during the
> * lookup, but it does need to be held while checking the MMU notifier.
> *
> @@ -4358,7 +4358,7 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
> return true;
>
> return fault->slot &&
> - mmu_invalidate_retry_hva(vcpu->kvm, fault->mmu_seq, fault->hva);
> + mmu_invalidate_retry_gfn(vcpu->kvm, fault->mmu_seq, fault->gfn);
> }
>
> static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> @@ -6245,7 +6245,9 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
>
> write_lock(&kvm->mmu_lock);
>
> - kvm_mmu_invalidate_begin(kvm, 0, -1ul);
> + kvm_mmu_invalidate_begin(kvm);
> +
> + kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end);
>
> flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end);
>
> @@ -6255,7 +6257,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> if (flush)
> kvm_flush_remote_tlbs_range(kvm, gfn_start, gfn_end - gfn_start);
>
> - kvm_mmu_invalidate_end(kvm, 0, -1ul);
> + kvm_mmu_invalidate_end(kvm);
>
> write_unlock(&kvm->mmu_lock);
> }
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 72e3943f3693..6e502ba93141 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6757,10 +6757,10 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
> return;
>
> /*
> - * Grab the memslot so that the hva lookup for the mmu_notifier retry
> - * is guaranteed to use the same memslot as the pfn lookup, i.e. rely
> - * on the pfn lookup's validation of the memslot to ensure a valid hva
> - * is used for the retry check.
> + * Explicitly grab the memslot using KVM's internal slot ID to ensure
> + * KVM doesn't unintentionally grab a userspace memslot. It _should_
> + * be impossible for userspace to create a memslot for the APIC when
> + * APICv is enabled, but paranoia won't hurt in this case.
> */
> slot = id_to_memslot(slots, APIC_ACCESS_PAGE_PRIVATE_MEMSLOT);
> if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
> @@ -6785,8 +6785,7 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
> return;
>
> read_lock(&vcpu->kvm->mmu_lock);
> - if (mmu_invalidate_retry_hva(kvm, mmu_seq,
> - gfn_to_hva_memslot(slot, gfn))) {
> + if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn)) {
> kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
> read_unlock(&vcpu->kvm->mmu_lock);
> goto out;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index fb6c6109fdca..11d091688346 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -787,8 +787,8 @@ struct kvm {
> struct mmu_notifier mmu_notifier;
> unsigned long mmu_invalidate_seq;
> long mmu_invalidate_in_progress;
> - unsigned long mmu_invalidate_range_start;
> - unsigned long mmu_invalidate_range_end;
> + gfn_t mmu_invalidate_range_start;
> + gfn_t mmu_invalidate_range_end;
> #endif
> struct list_head devices;
> u64 manual_dirty_log_protect;
> @@ -1392,10 +1392,9 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc);
> void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
> #endif
>
> -void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
> - unsigned long end);
> -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
> - unsigned long end);
> +void kvm_mmu_invalidate_begin(struct kvm *kvm);
> +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end);
What is the reason to separate range_add() from begin()?
> +void kvm_mmu_invalidate_end(struct kvm *kvm);
>
> long kvm_arch_dev_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg);
> @@ -1970,9 +1969,9 @@ static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq)
> return 0;
> }
>
> -static inline int mmu_invalidate_retry_hva(struct kvm *kvm,
> +static inline int mmu_invalidate_retry_gfn(struct kvm *kvm,
> unsigned long mmu_seq,
> - unsigned long hva)
> + gfn_t gfn)
> {
> lockdep_assert_held(&kvm->mmu_lock);
> /*
> @@ -1981,10 +1980,20 @@ static inline int mmu_invalidate_retry_hva(struct kvm *kvm,
> * that might be being invalidated. Note that it may include some false
> * positives, due to shortcuts when handing concurrent invalidations.
> */
> - if (unlikely(kvm->mmu_invalidate_in_progress) &&
> - hva >= kvm->mmu_invalidate_range_start &&
> - hva < kvm->mmu_invalidate_range_end)
> - return 1;
> + if (unlikely(kvm->mmu_invalidate_in_progress)) {
> + /*
> + * Dropping mmu_lock after bumping mmu_invalidate_in_progress
> + * but before updating the range is a KVM bug.
> + */
> + if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA ||
> + kvm->mmu_invalidate_range_end == INVALID_GPA))
> + return 1;
> +
> + if (gfn >= kvm->mmu_invalidate_range_start &&
> + gfn < kvm->mmu_invalidate_range_end)
> + return 1;
> + }
> +
> if (kvm->mmu_invalidate_seq != mmu_seq)
> return 1;
> return 0;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 5a97e6c7d9c2..1a577a25de47 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -543,9 +543,7 @@ static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
>
> typedef bool (*gfn_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range);
>
> -typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start,
> - unsigned long end);
> -
> +typedef void (*on_lock_fn_t)(struct kvm *kvm);
> typedef void (*on_unlock_fn_t)(struct kvm *kvm);
>
> struct kvm_mmu_notifier_range {
> @@ -637,7 +635,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
> locked = true;
> KVM_MMU_LOCK(kvm);
> if (!IS_KVM_NULL_FN(range->on_lock))
> - range->on_lock(kvm, range->start, range->end);
> + range->on_lock(kvm);
> +
> if (IS_KVM_NULL_FN(range->handler))
> break;
> }
> @@ -742,16 +741,29 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
> kvm_handle_hva_range(mn, address, address + 1, arg, kvm_change_spte_gfn);
> }
>
> -void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
> - unsigned long end)
> +void kvm_mmu_invalidate_begin(struct kvm *kvm)
> {
> + lockdep_assert_held_write(&kvm->mmu_lock);
> /*
> * The count increase must become visible at unlock time as no
> * spte can be established without taking the mmu_lock and
> * count is also read inside the mmu_lock critical section.
> */
> kvm->mmu_invalidate_in_progress++;
> +
> if (likely(kvm->mmu_invalidate_in_progress == 1)) {
> + kvm->mmu_invalidate_range_start = INVALID_GPA;
> + kvm->mmu_invalidate_range_end = INVALID_GPA;
I don't think this is incorrect, but I was a little suprised to see this
here rather than in end() when mmu_invalidate_in_progress decrements to
0.
> + }
> +}
> +
> +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end)
> +{
> + lockdep_assert_held_write(&kvm->mmu_lock);
Does this compile/function on KVM architectures with
!KVM_HAVE_MMU_RWLOCK? I assumed we would get an email from the buildbot
if it didn't compile but I don't know if buildbot builds with lockdep
enabled.
On this topic, I wonder if we should just bit the bullet and convert all
architectures to a rwlock_t.
> +
> + WARN_ON_ONCE(!kvm->mmu_invalidate_in_progress);
> +
> + if (likely(kvm->mmu_invalidate_range_start == INVALID_GPA)) {
> kvm->mmu_invalidate_range_start = start;
> kvm->mmu_invalidate_range_end = end;
> } else {
> @@ -771,6 +783,12 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start,
> }
> }
>
> +static bool kvm_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
> +{
> + kvm_mmu_invalidate_range_add(kvm, range->start, range->end);
> + return kvm_unmap_gfn_range(kvm, range);
> +}
> +
> static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
> const struct mmu_notifier_range *range)
> {
> @@ -778,7 +796,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
> const struct kvm_mmu_notifier_range hva_range = {
> .start = range->start,
> .end = range->end,
> - .handler = kvm_unmap_gfn_range,
> + .handler = kvm_mmu_unmap_gfn_range,
> .on_lock = kvm_mmu_invalidate_begin,
> .on_unlock = kvm_arch_guest_memory_reclaimed,
> .flush_on_ret = true,
> @@ -817,8 +835,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
> return 0;
> }
>
> -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
> - unsigned long end)
> +void kvm_mmu_invalidate_end(struct kvm *kvm)
> {
> /*
> * This sequence increase will notify the kvm page fault that
> @@ -834,6 +851,12 @@ void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
Let's add a lockdep_assert_held_write(&kvm->mmu_lock) here too while
we're at it?
> */
> kvm->mmu_invalidate_in_progress--;
> KVM_BUG_ON(kvm->mmu_invalidate_in_progress < 0, kvm);
> +
> + /*
> + * Assert that at least one range was added between start() and end().
> + * Not adding a range isn't fatal, but it is a KVM bug.
> + */
> + WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA);
> }
>
> static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
> --
> 2.42.0.820.g83a721a137-goog
>
On Mon, Oct 30, 2023 at 9:53 AM David Matlack <dmatlack@google.com> wrote: > > On 2023-10-27 11:21 AM, Sean Christopherson wrote: > > From: Chao Peng <chao.p.peng@linux.intel.com> > > > > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end); > > What is the reason to separate range_add() from begin()? Nevermind, I see how it's needed in kvm_mmu_unmap_gfn_range().
On Mon, Oct 30, 2023 at 5:53 PM David Matlack <dmatlack@google.com> wrote:
>
> On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> > From: Chao Peng <chao.p.peng@linux.intel.com>
> >
> > Currently in mmu_notifier invalidate path, hva range is recorded and
> > then checked against by mmu_notifier_retry_hva() in the page fault
> > handling path. However, for the to be introduced private memory, a page
> ^^^^^^^^^^^^^^^^^^^^^^^^
>
> Is there a missing word here?
No but there could be missing hyphens ("for the to-be-introduced
private memory"); possibly a "soon" could help parsing and that is
what you were talking about?
> > if (likely(kvm->mmu_invalidate_in_progress == 1)) {
> > + kvm->mmu_invalidate_range_start = INVALID_GPA;
> > + kvm->mmu_invalidate_range_end = INVALID_GPA;
>
> I don't think this is incorrect, but I was a little suprised to see this
> here rather than in end() when mmu_invalidate_in_progress decrements to
> 0.
I think that would be incorrect on the very first start?
> > + }
> > +}
> > +
> > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end)
> > +{
> > + lockdep_assert_held_write(&kvm->mmu_lock);
>
> Does this compile/function on KVM architectures with
> !KVM_HAVE_MMU_RWLOCK?
Yes:
#define lockdep_assert_held_write(l) \
lockdep_assert(lockdep_is_held_type(l, 0))
where 0 is the lock-held type used by lock_acquire_exclusive. In turn
is what you get for a spinlock or mutex, in addition to a rwlock or
rwsem that is taken for write.
Instead, lockdep_assert_held() asserts that the lock is taken without
asserting a particular lock-held type.
> > @@ -834,6 +851,12 @@ void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start,
>
> Let's add a lockdep_assert_held_write(&kvm->mmu_lock) here too while
> we're at it?
Yes, good idea.
Paolo
On Mon, Oct 30, 2023 at 10:01 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On Mon, Oct 30, 2023 at 5:53 PM David Matlack <dmatlack@google.com> wrote:
> >
> > On 2023-10-27 11:21 AM, Sean Christopherson wrote:
> > > From: Chao Peng <chao.p.peng@linux.intel.com>
> > >
> > > Currently in mmu_notifier invalidate path, hva range is recorded and
> > > then checked against by mmu_notifier_retry_hva() in the page fault
> > > handling path. However, for the to be introduced private memory, a page
> > ^^^^^^^^^^^^^^^^^^^^^^^^
> >
> > Is there a missing word here?
>
> No but there could be missing hyphens ("for the to-be-introduced
> private memory"); possibly a "soon" could help parsing and that is
> what you were talking about?
Ah that explains it :)
>
> > > if (likely(kvm->mmu_invalidate_in_progress == 1)) {
> > > + kvm->mmu_invalidate_range_start = INVALID_GPA;
> > > + kvm->mmu_invalidate_range_end = INVALID_GPA;
> >
> > I don't think this is incorrect, but I was a little suprised to see this
> > here rather than in end() when mmu_invalidate_in_progress decrements to
> > 0.
>
> I think that would be incorrect on the very first start?
Good point. KVM could initialize start/end before registering
notifiers, but that's extra code.
On 10/27/23 20:21, Sean Christopherson wrote: > From: Chao Peng <chao.p.peng@linux.intel.com> Currently in mmu_notifier > invalidate path, hva range is recorded and then checked against by > mmu_notifier_retry_hva() in the page fault handling path. However, for > the to be introduced private memory, a page fault may not have a hva > associated, checking gfn(gpa) makes more sense. For existing hva based > shared memory, gfn is expected to also work. The only downside is when > aliasing multiple gfns to a single hva, the current algorithm of > checking multiple ranges could result in a much larger range being > rejected. Such aliasing should be uncommon, so the impact is expected > small. Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Paolo
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