linux-kernel - [PATCH v1 1/5] KVM: arm64: Enable ring-based dirty memory tracking

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Date:   Fri, 19 Aug 2022 08:55:57 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org, peterx@...hat.com,
        pbonzini@...hat.com, corbet@....net, maz@...nel.org,
        james.morse@....com, alexandru.elisei@....com,
        suzuki.poulose@....com, oliver.upton@...ux.dev,
        catalin.marinas@....com, will@...nel.org, shuah@...nel.org,
        seanjc@...gle.com, drjones@...hat.com, dmatlack@...gle.com,
        bgardon@...gle.com, ricarkol@...gle.com, zhenyzha@...hat.com,
        shan.gavin@...il.com
Subject: [PATCH v1 1/5] KVM: arm64: Enable ring-based dirty memory tracking

The ring-based dirty memory tracking has been available and enabled
on x86 for a while. The feature is beneficial when the number of
dirty pages is small in a checkpointing system or live migration
scenario. More details can be found from fb04a1eddb1a ("KVM: X86:
Implement ring-based dirty memory tracking").

This enables the ring-based dirty memory tracking on ARM64. It's
notable that no extra reserved ring entries are needed on ARM64
because the huge pages are always split into base pages when page
dirty tracking is enabled.

Signed-off-by: Gavin Shan <gshan@...hat.com>
---
 Documentation/virt/kvm/api.rst    | 2 +-
 arch/arm64/include/uapi/asm/kvm.h | 1 +
 arch/arm64/kvm/Kconfig            | 1 +
 arch/arm64/kvm/arm.c              | 8 ++++++++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index abd7c32126ce..19fa1ac017ed 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8022,7 +8022,7 @@ regardless of what has actually been exposed through the CPUID leaf.
 8.29 KVM_CAP_DIRTY_LOG_RING
 ---------------------------
 
-:Architectures: x86
+:Architectures: x86, arm64
 :Parameters: args[0] - size of the dirty log ring
 
 KVM is capable of tracking dirty memory using ring buffers that are
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 3bb134355874..7e04b0b8d2b2 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -43,6 +43,7 @@
 #define __KVM_HAVE_VCPU_EVENTS
 
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
+#define KVM_DIRTY_LOG_PAGE_OFFSET 64
 
 #define KVM_REG_SIZE(id)						\
 	(1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 815cc118c675..0309b2d0f2da 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -32,6 +32,7 @@ menuconfig KVM
 	select KVM_VFIO
 	select HAVE_KVM_EVENTFD
 	select HAVE_KVM_IRQFD
+	select HAVE_KVM_DIRTY_RING
 	select HAVE_KVM_MSI
 	select HAVE_KVM_IRQCHIP
 	select HAVE_KVM_IRQ_ROUTING
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 986cee6fbc7f..3de6b9b39db7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -866,6 +866,14 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		if (!ret)
 			ret = 1;
 
+		/* Force vcpu exit if its dirty ring is soft-full */
+		if (unlikely(vcpu->kvm->dirty_ring_size &&
+			     kvm_dirty_ring_soft_full(&vcpu->dirty_ring))) {
+			vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
+			trace_kvm_dirty_ring_exit(vcpu);
+			ret = 0;
+		}
+
 		if (ret > 0)
 			ret = check_vcpu_requests(vcpu);
 
-- 
2.23.0