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From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Christophe de Dinechin <dinechin@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Kevin Tian <kevin.tian@intel.com>,
	peterx@redhat.com,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Yan Zhao <yan.y.zhao@intel.com>
Subject: [PATCH v9 06/14] KVM: Make dirty ring exclusive to dirty bitmap log
Date: Sat, 23 May 2020 18:56:51 -0400
Message-ID: <20200523225659.1027044-7-peterx@redhat.com> (raw)
In-Reply-To: <20200523225659.1027044-1-peterx@redhat.com>

There's no good reason to use both the dirty bitmap logging and the
new dirty ring buffer to track dirty bits.  We should be able to even
support both of them at the same time, but it could complicate things
which could actually help little.  Let's simply make it the rule
before we enable dirty ring on any arch, that we don't allow these two
interfaces to be used together.

The big world switch would be KVM_CAP_DIRTY_LOG_RING capability
enablement.  That's where we'll switch from the default dirty logging
way to the dirty ring way.  As long as kvm->dirty_ring_size is setup
correctly, we'll once and for all switch to the dirty ring buffer mode
for the current virtual machine.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 Documentation/virt/kvm/api.rst |  7 +++++++
 virt/kvm/kvm_main.c            | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aa54a34077b7..d56f86ba05a0 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6225,3 +6225,10 @@ make sure all the existing dirty gfns are flushed to the dirty rings.
 
 The dirty ring can gets full.  When it happens, the KVM_RUN of the
 vcpu will return with exit reason KVM_EXIT_DIRTY_LOG_FULL.
+
+NOTE: the capability KVM_CAP_DIRTY_LOG_RING and the corresponding
+ioctl KVM_RESET_DIRTY_RINGS are mutual exclusive to the existing ioctl
+KVM_GET_DIRTY_LOG.  After enabling KVM_CAP_DIRTY_LOG_RING with an
+acceptable dirty ring size, the virtual machine will switch to the
+dirty ring tracking mode.  Further ioctls to either KVM_GET_DIRTY_LOG
+or KVM_CLEAR_DIRTY_LOG will fail.
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index daca53ed5a74..9639cf8d8c9c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1355,6 +1355,10 @@ int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
 	unsigned long n;
 	unsigned long any = 0;
 
+	/* Dirty ring tracking is exclusive to dirty log tracking */
+	if (kvm->dirty_ring_size)
+		return -EINVAL;
+
 	*memslot = NULL;
 	*is_dirty = 0;
 
@@ -1416,6 +1420,10 @@ static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
 	unsigned long *dirty_bitmap_buffer;
 	bool flush;
 
+	/* Dirty ring tracking is exclusive to dirty log tracking */
+	if (kvm->dirty_ring_size)
+		return -EINVAL;
+
 	as_id = log->slot >> 16;
 	id = (u16)log->slot;
 	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
@@ -1524,6 +1532,10 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm,
 	unsigned long *dirty_bitmap_buffer;
 	bool flush;
 
+	/* Dirty ring tracking is exclusive to dirty log tracking */
+	if (kvm->dirty_ring_size)
+		return -EINVAL;
+
 	as_id = log->slot >> 16;
 	id = (u16)log->slot;
 	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
-- 
2.26.2


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-23 22:56 [PATCH v9 00/14] KVM: Dirty ring interface Peter Xu
2020-05-23 22:56 ` [PATCH v9 01/14] KVM: X86: Change parameter for fast_page_fault tracepoint Peter Xu
2020-05-23 22:56 ` [PATCH v9 02/14] KVM: Cache as_id in kvm_memory_slot Peter Xu
2020-05-23 22:56 ` [PATCH v9 03/14] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR] Peter Xu
2020-05-23 22:56 ` [PATCH v9 04/14] KVM: Pass in kvm pointer into mark_page_dirty_in_slot() Peter Xu
2020-05-23 22:56 ` [PATCH v9 05/14] KVM: X86: Implement ring-based dirty memory tracking Peter Xu
2020-05-25  2:48   ` kbuild test robot
2020-05-25 15:26     ` Peter Xu
     [not found]   ` <202005252245.ZeOB8qNJ%lkp@intel.com>
2020-05-25 15:33     ` Peter Xu
2020-05-23 22:56 ` Peter Xu [this message]
2020-05-23 22:56 ` [PATCH v9 07/14] KVM: Don't allocate dirty bitmap if dirty ring is enabled Peter Xu
2020-05-26 15:05   ` kbuild test robot
2020-05-26 15:21     ` Peter Xu
2020-05-23 22:56 ` [PATCH v9 08/14] KVM: selftests: Always clear dirty bitmap after iteration Peter Xu
2020-05-23 22:56 ` [PATCH v9 09/14] KVM: selftests: Sync uapi/linux/kvm.h to tools/ Peter Xu
2020-05-23 22:56 ` [PATCH v9 10/14] KVM: selftests: Use a single binary for dirty/clear log test Peter Xu
2020-05-23 22:56 ` [PATCH v9 11/14] KVM: selftests: Introduce after_vcpu_run hook for dirty " Peter Xu
2020-05-23 22:56 ` [PATCH v9 12/14] KVM: selftests: Add dirty ring buffer test Peter Xu
2020-05-23 23:06 ` [PATCH v9 13/14] KVM: selftests: Let dirty_log_test async for dirty ring test Peter Xu
2020-05-23 23:06 ` [PATCH v9 14/14] KVM: selftests: Add "-c" parameter to dirty log test Peter Xu
2020-05-23 23:14 ` [PATCH v9 00/14] KVM: Dirty ring interface Peter Xu

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