diff mbox series

[v12,04/20] KVM: pfncache: add a mark-dirty helper

Message ID 20240115125707.1183-5-paul@xen.org (mailing list archive)
State New, archived
Headers show
Series KVM: xen: update shared_info and vcpu_info handling | expand

Commit Message

Paul Durrant Jan. 15, 2024, 12:56 p.m. UTC 
From: Paul Durrant <pdurrant@amazon.com>

At the moment pages are marked dirty by open-coded calls to
mark_page_dirty_in_slot(), directly deferefencing the gpa and memslot
from the cache. After a subsequent patch these may not always be set
so add a helper now so that caller will protected from the need to know
about this detail.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org

v8:
 - Make the helper a static inline.
---
 arch/x86/kvm/x86.c       |  2 +-
 arch/x86/kvm/xen.c       |  6 +++---
 include/linux/kvm_host.h | 11 +++++++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

Comments

Sean Christopherson Feb. 7, 2024, 3:20 a.m. UTC | #1 
On Mon, Jan 15, 2024, Paul Durrant wrote:
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7e7fd25b09b3..f3bb9e0a81fe 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1399,6 +1399,17 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
>   */
>  void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>  
> +/**
> + * kvm_gpc_mark_dirty - mark a cached page as dirty.
> + *
> + * @gpc:	   struct gfn_to_pfn_cache object.
> + */
> +static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)

Any objection to kvm_gpc_mark_dirty_in_slot()?  I want to make it clear this only
marks the gfn dirty in the memslot, i.e. that it doesn't mark the underlying page
as dirty.
Paul Durrant Feb. 7, 2024, 8:47 a.m. UTC | #2 
On 07/02/2024 03:20, Sean Christopherson wrote:
> On Mon, Jan 15, 2024, Paul Durrant wrote:
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index 7e7fd25b09b3..f3bb9e0a81fe 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -1399,6 +1399,17 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
>>    */
>>   void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>>   
>> +/**
>> + * kvm_gpc_mark_dirty - mark a cached page as dirty.
>> + *
>> + * @gpc:	   struct gfn_to_pfn_cache object.
>> + */
>> +static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
> 
> Any objection to kvm_gpc_mark_dirty_in_slot()?  I want to make it clear this only
> marks the gfn dirty in the memslot, i.e. that it doesn't mark the underlying page
> as dirty.

Ok, that sounds fair.

   Paul
Sean Christopherson Feb. 9, 2024, 3:58 p.m. UTC | #3 
On Mon, Jan 15, 2024, Paul Durrant wrote:
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 7e7fd25b09b3..f3bb9e0a81fe 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1399,6 +1399,17 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
>   */
>  void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>  
> +/**
> + * kvm_gpc_mark_dirty - mark a cached page as dirty.
> + *
> + * @gpc:	   struct gfn_to_pfn_cache object.
> + */
> +static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
> +{
> +	lockdep_assert_held(&gpc->lock);
> +	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);

Can you opportunistically have this pre-check gpc->memslot?  __kvm_gpc_refresh()
should nullify gpc->memslot when using an hva.  That way, you don't need to
explicitly check for the "invalid gfn" case here (or you could, but WARN_ON_ONCE()
if the memslot is non-NULL and the gfn is invalid?).
Paul Durrant Feb. 9, 2024, 4:05 p.m. UTC | #4 
On 09/02/2024 15:58, Sean Christopherson wrote:
> On Mon, Jan 15, 2024, Paul Durrant wrote:
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index 7e7fd25b09b3..f3bb9e0a81fe 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -1399,6 +1399,17 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
>>    */
>>   void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
>>   
>> +/**
>> + * kvm_gpc_mark_dirty - mark a cached page as dirty.
>> + *
>> + * @gpc:	   struct gfn_to_pfn_cache object.
>> + */
>> +static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
>> +{
>> +	lockdep_assert_held(&gpc->lock);
>> +	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
> 
> Can you opportunistically have this pre-check gpc->memslot?  __kvm_gpc_refresh()
> should nullify gpc->memslot when using an hva.  That way, you don't need to
> explicitly check for the "invalid gfn" case here (or you could, but WARN_ON_ONCE()
> if the memslot is non-NULL and the gfn is invalid?).

Ok, sure.
diff mbox series

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 27e23714e960..0a0ac91a494f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3156,7 +3156,7 @@  static void kvm_setup_guest_pvclock(struct kvm_vcpu *v,
 
 	guest_hv_clock->version = ++vcpu->hv_clock.version;
 
-	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+	kvm_gpc_mark_dirty(gpc);
 	read_unlock_irqrestore(&gpc->lock, flags);
 
 	trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock);
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index b63bf54bb376..34c48d0029c1 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -453,11 +453,11 @@  static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic)
 	}
 
 	if (user_len2) {
-		mark_page_dirty_in_slot(v->kvm, gpc2->memslot, gpc2->gpa >> PAGE_SHIFT);
+		kvm_gpc_mark_dirty(gpc2);
 		read_unlock(&gpc2->lock);
 	}
 
-	mark_page_dirty_in_slot(v->kvm, gpc1->memslot, gpc1->gpa >> PAGE_SHIFT);
+	kvm_gpc_mark_dirty(gpc1);
 	read_unlock_irqrestore(&gpc1->lock, flags);
 }
 
@@ -565,7 +565,7 @@  void kvm_xen_inject_pending_events(struct kvm_vcpu *v)
 		WRITE_ONCE(vi->evtchn_upcall_pending, 1);
 	}
 
-	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+	kvm_gpc_mark_dirty(gpc);
 	read_unlock_irqrestore(&gpc->lock, flags);
 
 	/* For the per-vCPU lapic vector, deliver it as MSI. */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7e7fd25b09b3..f3bb9e0a81fe 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1399,6 +1399,17 @@  int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);
  */
 void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);
 
+/**
+ * kvm_gpc_mark_dirty - mark a cached page as dirty.
+ *
+ * @gpc:	   struct gfn_to_pfn_cache object.
+ */
+static inline void kvm_gpc_mark_dirty(struct gfn_to_pfn_cache *gpc)
+{
+	lockdep_assert_held(&gpc->lock);
+	mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);
+}
+
 void kvm_sigset_activate(struct kvm_vcpu *vcpu);
 void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);