[PATCH v4 0/4] Improve dirty ring warning report

[PATCH v4 0/4] Improve dirty ring warning report

[Gavin Shan]

It has been known case where no running VCPU context exists when the
vgic/its tables are saved. There are other two unknown cases where we
don't have the running VCPU context: (a) restore VGICv3 LPI pending
status. (b) restoring VGICv3 pending tables.

PATCH[1]     includes 'kvm_mmu.h' to 'vgic.h'
PATCH[2]     adds unified helper vgic_write_guest_lock()
PATCH[3 - 4] allows no-running-vcpu context for (a) and (b)

v3: https://lore.kernel.org/kvmarm/20230126235451.469087-1-gshan@redhat.com/T/#t
v2: https://lore.kernel.org/kvmarm/Y9Lg1ESUVJov0WpH@google.com/T/#t
v1: https://lore.kernel.org/kvmarm/20230116040405.260935-1-gshan@redhat.com/T/#t

Changelog
=========
v4:
  * s/vgic3/VGICv3                                             (Zenghui)
  * s/save_tables_in_progress/write_tables_in_progress         (Zenghui)
v3:
  * Pick Oliver's r-bs
  * Include 'kvm_mmu.h' to 'vgic.h'                            (Oliver)
v2:
  * Add unified helper vgic_write_guest_lock()                 (Oliver)
  * Dropped two patches to refactor mark_page_dirty_in_slot()  (Sean)

Gavin Shan (4):
  KVM: arm64: Include kvm_mmu.h from vgic.h
  KVM: arm64: Add helper vgic_write_guest_lock()
  KVM: arm64: Allow no running vcpu on restoring VGICv3 LPI pending
    status
  KVM: arm64: Allow no running vcpu on saving VGICv3 pending table

 Documentation/virt/kvm/api.rst        | 10 +++++++---
 arch/arm64/kvm/vgic/vgic-debug.c      |  1 -
 arch/arm64/kvm/vgic/vgic-init.c       |  1 -
 arch/arm64/kvm/vgic/vgic-its.c        | 14 +++++---------
 arch/arm64/kvm/vgic/vgic-kvm-device.c |  1 -
 arch/arm64/kvm/vgic/vgic-mmio-v3.c    |  1 -
 arch/arm64/kvm/vgic/vgic-v2.c         |  1 -
 arch/arm64/kvm/vgic/vgic-v3.c         |  5 ++---
 arch/arm64/kvm/vgic/vgic.h            | 14 ++++++++++++++
 include/kvm/arm_vgic.h                |  2 +-
 10 files changed, 29 insertions(+), 21 deletions(-)

-- 
2.23.0

[PATCH v4 1/4] KVM: arm64: Include kvm_mmu.h from vgic.h

[Gavin Shan]

We need a unified helper in 'kvm/vgic/vgic.h' to write guest memory. In
the helper, the check of no-running-vcpu context for dirty ring will be
applied. kvm_write_guest_lock(), defined in 'include/asm/kvm_mmu.h', is
going to be dereferenced by the unified helper.

Include 'include/asm/kvm_mmu.h' to 'kvm/vgic/vgic.h' to avoid including
the former header file when the later one is needed. With the change,
the duplicate inclusions of 'include/asm/kvm_mmu.h' are removed.

No functional change intended.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Gavin Shan <gshan@redhat.com>
---
 arch/arm64/kvm/vgic/vgic-debug.c      | 1 -
 arch/arm64/kvm/vgic/vgic-init.c       | 1 -
 arch/arm64/kvm/vgic/vgic-its.c        | 1 -
 arch/arm64/kvm/vgic/vgic-kvm-device.c | 1 -
 arch/arm64/kvm/vgic/vgic-mmio-v3.c    | 1 -
 arch/arm64/kvm/vgic/vgic-v2.c         | 1 -
 arch/arm64/kvm/vgic/vgic-v3.c         | 1 -
 arch/arm64/kvm/vgic/vgic.h            | 1 +
 8 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-debug.c b/arch/arm64/kvm/vgic/vgic-debug.c
index 78cde687383c..69201c2dfc6c 100644
--- a/arch/arm64/kvm/vgic/vgic-debug.c
+++ b/arch/arm64/kvm/vgic/vgic-debug.c
@@ -10,7 +10,6 @@
 #include <linux/kvm_host.h>
 #include <linux/seq_file.h>
 #include <kvm/arm_vgic.h>
-#include <asm/kvm_mmu.h>
 #include "vgic.h"
 
 /*
diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index f6d4f4052555..de389a5bec45 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -9,7 +9,6 @@
 #include <linux/kvm_host.h>
 #include <kvm/arm_vgic.h>
 #include <asm/kvm_emulate.h>
-#include <asm/kvm_mmu.h>
 #include "vgic.h"
 
 /*
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 94a666dd1443..ad4bb69ab83e 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -18,7 +18,6 @@
 
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_arm.h>
-#include <asm/kvm_mmu.h>
 
 #include "vgic.h"
 #include "vgic-mmio.h"
diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index edeac2380591..552668a91bd9 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -8,7 +8,6 @@
 #include <linux/kvm_host.h>
 #include <kvm/arm_vgic.h>
 #include <linux/uaccess.h>
-#include <asm/kvm_mmu.h>
 #include <asm/cputype.h>
 #include "vgic.h"
 
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index 91201f743033..8ba04f4fa63d 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -13,7 +13,6 @@
 
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_arm.h>
-#include <asm/kvm_mmu.h>
 
 #include "vgic.h"
 #include "vgic-mmio.h"
diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
index 645648349c99..d8604fdfdfcd 100644
--- a/arch/arm64/kvm/vgic/vgic-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-v2.c
@@ -7,7 +7,6 @@
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 #include <kvm/arm_vgic.h>
-#include <asm/kvm_mmu.h>
 
 #include "vgic.h"
 
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 2074521d4a8c..5dfbd03e5e1a 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -7,7 +7,6 @@
 #include <linux/kvm_host.h>
 #include <kvm/arm_vgic.h>
 #include <asm/kvm_hyp.h>
-#include <asm/kvm_mmu.h>
 #include <asm/kvm_asm.h>
 
 #include "vgic.h"
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index 0c8da72953f0..056425e3a490 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -6,6 +6,7 @@
 #define __KVM_ARM_VGIC_NEW_H__
 
 #include <linux/irqchip/arm-gic-common.h>
+#include <asm/kvm_mmu.h>
 
 #define PRODUCT_ID_KVM		0x4b	/* ASCII code K */
 #define IMPLEMENTER_ARM		0x43b
-- 
2.23.0

Re: [PATCH v4 1/4] KVM: arm64: Include kvm_mmu.h from vgic.h

[Oliver Upton]

On Sat, Jan 28, 2023 at 07:51:47AM +0800, Gavin Shan wrote:
> We need a unified helper in 'kvm/vgic/vgic.h' to write guest memory. In
> the helper, the check of no-running-vcpu context for dirty ring will be
> applied. kvm_write_guest_lock(), defined in 'include/asm/kvm_mmu.h', is
> going to be dereferenced by the unified helper.
> 
> Include 'include/asm/kvm_mmu.h' to 'kvm/vgic/vgic.h' to avoid including
> the former header file when the later one is needed. With the change,
> the duplicate inclusions of 'include/asm/kvm_mmu.h' are removed.
> 
> No functional change intended.
> 
> Suggested-by: Oliver Upton <oliver.upton@linux.dev>

No, I did not suggest for you to do this. I had suggested you just
include asm/kvm_mmu.h from the vgic header, not to go and remove it from
all the files that include vgic.h.

Who cares if kvm_mmu.h gets included twice? Include guards exist for this
exact reason.

-- 
Thanks,
Oliver

Re: [PATCH v4 1/4] KVM: arm64: Include kvm_mmu.h from vgic.h

[Gavin Shan]

Hi Oliver,

On 1/28/23 11:14 AM, Oliver Upton wrote:
> On Sat, Jan 28, 2023 at 07:51:47AM +0800, Gavin Shan wrote:
>> We need a unified helper in 'kvm/vgic/vgic.h' to write guest memory. In
>> the helper, the check of no-running-vcpu context for dirty ring will be
>> applied. kvm_write_guest_lock(), defined in 'include/asm/kvm_mmu.h', is
>> going to be dereferenced by the unified helper.
>>
>> Include 'include/asm/kvm_mmu.h' to 'kvm/vgic/vgic.h' to avoid including
>> the former header file when the later one is needed. With the change,
>> the duplicate inclusions of 'include/asm/kvm_mmu.h' are removed.
>>
>> No functional change intended.
>>
>> Suggested-by: Oliver Upton <oliver.upton@linux.dev>
> 
> No, I did not suggest for you to do this. I had suggested you just
> include asm/kvm_mmu.h from the vgic header, not to go and remove it from
> all the files that include vgic.h.
> 
> Who cares if kvm_mmu.h gets included twice? Include guards exist for this
> exact reason.
> 

Ok, I misundertood your suggestion. Could you drop PATCH[v4 1/4] and include
'kvm_mmu.h' to 'vgic.h'? Otherwise, I need to respin for v5. Please let me
know your preference.

Thanks,
Gavin

[PATCH v4 2/4] KVM: arm64: Add helper vgic_write_guest_lock()

[Gavin Shan]

Currently, the unknown no-running-vcpu sites are reported when a
dirty page is tracked by mark_page_dirty_in_slot(). Until now, the
only known no-running-vcpu site is saving vgic/its tables through
KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_SAVE_TABLES} command on KVM device
"kvm-arm-vgic-its". Unfortunately, there are more unknown sites to
be handled and no-running-vcpu context will be allowed in these
sites: (1) KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_RESTORE_TABLES} command
on KVM device "kvm-arm-vgic-its" to restore vgic/its tables. The
VGICv3 LPI pending status could be restored. (2) Save VGICv3 pending
table through KVM_DEV_ARM_{VGIC_GRP_CTRL, VGIC_SAVE_PENDING_TABLES}
command on KVM device "kvm-arm-vgic-v3".

To handle those unknown cases, an unified handler vgic_write_guest_lock()
is introduced. struct vgic_dist::save_its_tables_in_progress is also
renamed to struct vgic_dist::write_tables_in_progress.

No functional change intended.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/vgic/vgic-its.c | 13 +++++--------
 arch/arm64/kvm/vgic/vgic.h     | 13 +++++++++++++
 include/kvm/arm_vgic.h         |  2 +-
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index ad4bb69ab83e..bad8ed6dcaa4 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -2186,7 +2186,7 @@ static int vgic_its_save_ite(struct vgic_its *its, struct its_device *dev,
 	       ((u64)ite->irq->intid << KVM_ITS_ITE_PINTID_SHIFT) |
 		ite->collection->collection_id;
 	val = cpu_to_le64(val);
-	return kvm_write_guest_lock(kvm, gpa, &val, ite_esz);
+	return vgic_write_guest_lock(kvm, gpa, &val, ite_esz);
 }
 
 /**
@@ -2338,7 +2338,7 @@ static int vgic_its_save_dte(struct vgic_its *its, struct its_device *dev,
 	       (itt_addr_field << KVM_ITS_DTE_ITTADDR_SHIFT) |
 		(dev->num_eventid_bits - 1));
 	val = cpu_to_le64(val);
-	return kvm_write_guest_lock(kvm, ptr, &val, dte_esz);
+	return vgic_write_guest_lock(kvm, ptr, &val, dte_esz);
 }
 
 /**
@@ -2525,7 +2525,7 @@ static int vgic_its_save_cte(struct vgic_its *its,
 	       ((u64)collection->target_addr << KVM_ITS_CTE_RDBASE_SHIFT) |
 	       collection->collection_id);
 	val = cpu_to_le64(val);
-	return kvm_write_guest_lock(its->dev->kvm, gpa, &val, esz);
+	return vgic_write_guest_lock(its->dev->kvm, gpa, &val, esz);
 }
 
 /*
@@ -2606,7 +2606,7 @@ static int vgic_its_save_collection_table(struct vgic_its *its)
 	 */
 	val = 0;
 	BUG_ON(cte_esz > sizeof(val));
-	ret = kvm_write_guest_lock(its->dev->kvm, gpa, &val, cte_esz);
+	ret = vgic_write_guest_lock(its->dev->kvm, gpa, &val, cte_esz);
 	return ret;
 }
 
@@ -2742,7 +2742,6 @@ static int vgic_its_has_attr(struct kvm_device *dev,
 static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
 {
 	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
-	struct vgic_dist *dist = &kvm->arch.vgic;
 	int ret = 0;
 
 	if (attr == KVM_DEV_ARM_VGIC_CTRL_INIT) /* Nothing to do */
@@ -2762,9 +2761,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
 		vgic_its_reset(kvm, its);
 		break;
 	case KVM_DEV_ARM_ITS_SAVE_TABLES:
-		dist->save_its_tables_in_progress = true;
 		ret = abi->save_tables(its);
-		dist->save_its_tables_in_progress = false;
 		break;
 	case KVM_DEV_ARM_ITS_RESTORE_TABLES:
 		ret = abi->restore_tables(its);
@@ -2791,7 +2788,7 @@ bool kvm_arch_allow_write_without_running_vcpu(struct kvm *kvm)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
 
-	return dist->save_its_tables_in_progress;
+	return dist->write_tables_in_progress;
 }
 
 static int vgic_its_set_attr(struct kvm_device *dev,
diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index 056425e3a490..e578a296e7e0 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -132,6 +132,19 @@ static inline bool vgic_irq_is_multi_sgi(struct vgic_irq *irq)
 	return vgic_irq_get_lr_count(irq) > 1;
 }
 
+static inline int vgic_write_guest_lock(struct kvm *kvm, gpa_t gpa,
+					const void *data, unsigned long len)
+{
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	int ret;
+
+	dist->write_tables_in_progress = true;
+	ret = kvm_write_guest_lock(kvm, gpa, data, len);
+	dist->write_tables_in_progress = false;
+
+	return ret;
+}
+
 /*
  * This struct provides an intermediate representation of the fields contained
  * in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 9270cd87da3f..f009c04b3066 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -263,7 +263,7 @@ struct vgic_dist {
 	struct vgic_io_device	dist_iodev;
 
 	bool			has_its;
-	bool			save_its_tables_in_progress;
+	bool			write_tables_in_progress;
 
 	/*
 	 * Contains the attributes and gpa of the LPI configuration table.
-- 
2.23.0

[PATCH v4 3/4] KVM: arm64: Allow no running vcpu on restoring VGICv3 LPI pending status

[Gavin Shan]

We don't have a running VCPU context to restore VGICv3 LPI pending status
due to command KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_RESTORE_TABLES} on KVM
device "kvm-arm-vgic-its".

Use vgic_write_guest_lock() to restore VGICv3 LPI pending status.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
---
 Documentation/virt/kvm/api.rst | 8 +++++---
 arch/arm64/kvm/vgic/vgic-v3.c  | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9807b05a1b57..5dc3598afbe2 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8070,9 +8070,11 @@ considering the state as complete. VMM needs to ensure that the dirty
 state is final and avoid missing dirty pages from another ioctl ordered
 after the bitmap collection.
 
-NOTE: One example of using the backup bitmap is saving arm64 vgic/its
-tables through KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_SAVE_TABLES} command on
-KVM device "kvm-arm-vgic-its" when dirty ring is enabled.
+NOTE: Multiple examples of using the backup bitmap: (1) save vgic/its
+tables through command KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_SAVE_TABLES} on
+KVM device "kvm-arm-vgic-its". (2) restore vgic/its tables through
+command KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_RESTORE_TABLES} on KVM device
+"kvm-arm-vgic-its". VGICv3 LPI pending status is restored.
 
 8.30 KVM_CAP_XEN_HVM
 --------------------
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 5dfbd03e5e1a..c94e4d7520fc 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -338,7 +338,7 @@ int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
 	if (status) {
 		/* clear consumed data */
 		val &= ~(1 << bit_nr);
-		ret = kvm_write_guest_lock(kvm, ptr, &val, 1);
+		ret = vgic_write_guest_lock(kvm, ptr, &val, 1);
 		if (ret)
 			return ret;
 	}
-- 
2.23.0

[PATCH v4 4/4] KVM: arm64: Allow no running vcpu on saving VGICv3 pending table

[Gavin Shan]

We don't have a running VCPU context to save VGICv3 pending table due
to KVM_DEV_ARM_VGIC_{GRP_CTRL, SAVE_PENDING_TABLES} command on KVM
device "kvm-arm-vgic-v3". The unknown case is caught by kvm-unit-tests.

   # ./kvm-unit-tests/tests/its-pending-migration
   WARNING: CPU: 120 PID: 7973 at arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3325 \
   mark_page_dirty_in_slot+0x60/0xe0
    :
   mark_page_dirty_in_slot+0x60/0xe0
   __kvm_write_guest_page+0xcc/0x100
   kvm_write_guest+0x7c/0xb0
   vgic_v3_save_pending_tables+0x148/0x2a0
   vgic_set_common_attr+0x158/0x240
   vgic_v3_set_attr+0x4c/0x5c
   kvm_device_ioctl+0x100/0x160
   __arm64_sys_ioctl+0xa8/0xf0
   invoke_syscall.constprop.0+0x7c/0xd0
   el0_svc_common.constprop.0+0x144/0x160
   do_el0_svc+0x34/0x60
   el0_svc+0x3c/0x1a0
   el0t_64_sync_handler+0xb4/0x130
   el0t_64_sync+0x178/0x17c

Use vgic_write_guest_lock() to save VGICv3 pending table.

Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
---
 Documentation/virt/kvm/api.rst | 4 +++-
 arch/arm64/kvm/vgic/vgic-v3.c  | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 5dc3598afbe2..d653e13954d9 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8074,7 +8074,9 @@ NOTE: Multiple examples of using the backup bitmap: (1) save vgic/its
 tables through command KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_SAVE_TABLES} on
 KVM device "kvm-arm-vgic-its". (2) restore vgic/its tables through
 command KVM_DEV_ARM_{VGIC_GRP_CTRL, ITS_RESTORE_TABLES} on KVM device
-"kvm-arm-vgic-its". VGICv3 LPI pending status is restored.
+"kvm-arm-vgic-its". VGICv3 LPI pending status is restored. (3) save
+VGICv3 pending table through KVM_DEV_ARM_VGIC_{GRP_CTRL, SAVE_PENDING_TABLES}
+command on KVM device "kvm-arm-vgic-v3".
 
 8.30 KVM_CAP_XEN_HVM
 --------------------
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index c94e4d7520fc..558ccc805fff 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -436,7 +436,7 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
 		else
 			val &= ~(1 << bit_nr);
 
-		ret = kvm_write_guest_lock(kvm, ptr, &val, 1);
+		ret = vgic_write_guest_lock(kvm, ptr, &val, 1);
 		if (ret)
 			goto out;
 	}
-- 
2.23.0