linux-kernel - [PATCH v2 2/5] KVM: arm64: Enable ring-based dirty memory tracking

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Message-Id: <20220916045135.154505-3-gshan@redhat.com>
Date:   Fri, 16 Sep 2022 12:51:32 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        catalin.marinas@....com, linux-kselftest@...r.kernel.org,
        bgardon@...gle.com, shuah@...nel.org, corbet@....net,
        maz@...nel.org, drjones@...hat.com, will@...nel.org,
        zhenyzha@...hat.com, dmatlack@...gle.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, peterx@...hat.com, oliver.upton@...ux.dev,
        shan.gavin@...il.com
Subject: [PATCH v2 2/5] KVM: arm64: Enable ring-based dirty memory tracking

This enables the ring-based dirty memory tracking on ARM64. The
feature is configured by CONFIG_HAVE_KVM_DIRTY_RING, detected and
enabled by KVM_CAP_DIRTY_LOG_RING. A ring buffer is created on every
VCPU when the feature is enabled. Each entry in the ring buffer is
described by 'struct kvm_dirty_gfn'.

A ring buffer entry is pushed when a page becomes dirty on host,
and pulled by userspace after the ring buffer is mapped at physical
page offset KVM_DIRTY_LOG_PAGE_OFFSET. The specific VCPU is enforced
to exit if its ring buffer becomes softly full. Besides, the ring
buffer can be reset by ioctl command KVM_RESET_DIRTY_RINGS to release
those pulled ring buffer entries.

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 316917b98707..a7a857f1784d 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 2ff0ef62abad..76816f8e082b 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -747,6 +747,14 @@ static int check_vcpu_requests(struct kvm_vcpu *vcpu)
 
 		if (kvm_check_request(KVM_REQ_SUSPEND, vcpu))
 			return kvm_vcpu_suspend(vcpu);
+
+		if (kvm_check_request(KVM_REQ_RING_SOFT_FULL, vcpu) &&
+		    kvm_dirty_ring_soft_full(&vcpu->dirty_ring)) {
+			kvm_make_request(KVM_REQ_RING_SOFT_FULL, vcpu);
+			vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
+			trace_kvm_dirty_ring_exit(vcpu);
+			return 0;
+		}
 	}
 
 	return 1;
-- 
2.23.0