[PATCH v4 0/2] KVM: s390: make use of ultravisor AIV support

[PATCH v4 0/2] KVM: s390: make use of ultravisor AIV support

[Michael Mueller]

This patch enables the ultravisor adapter interruption vitualization
support.

Changes in v4:
- All vcpus are pulled out of SIE and disbled before the control
  blocks are changed to disable/enable the gisa and re-enabled
  afterwards instead of taking the vcpu specific lock.

Changes in v3:
- cache and test GISA descriptor only once in kvm_s390_gisa_enable()
- modified some comments
- removed some whitespace issues

Changes in v2:
- moved GISA disable into "put CPUs in PV mode" routine
- moved GISA enable into "pull CPUs out of PV mode" routine 

[1] https://lore.kernel.org/lkml/ae7c65d8-f632-a7f4-926a-50b9660673a1@linux.ibm.com/T/#mcb67699bf458ba7482f6b7529afe589d1dbb5930
[2] https://lore.kernel.org/all/20220208165310.3905815-1-mimu@linux.ibm.com/
[3] https://lore.kernel.org/all/20220209152217.1793281-2-mimu@linux.ibm.com/

Michael Mueller (2):
  KVM: s390: pv: pull all vcpus out of SIE before converting to/from pv
    vcpu
  KVM: s390: pv: make use of ultravisor AIV support

 arch/s390/include/asm/uv.h |  1 +
 arch/s390/kvm/interrupt.c  | 54 +++++++++++++++++++++++++++++++++-----
 arch/s390/kvm/kvm-s390.c   | 19 +++++++++-----
 arch/s390/kvm/kvm-s390.h   | 11 ++++++++
 4 files changed, 72 insertions(+), 13 deletions(-)

-- 
2.32.0

[PATCH v4 1/2] KVM: s390: pv: pull all vcpus out of SIE before converting to/from pv vcpu

[Michael Mueller]

That will allow to modify the control blocks without locking the vcpus.
A kvm-unit-test surfaced a possible DEADLOCK situation when guest cpus are
executing intercepted instructions at this time.

[  319.799638] ======================================================
[  319.799639] WARNING: possible circular locking dependency detected
[  319.799641] 5.17.0-rc5-08427-gfd14b6309198 #4661 Not tainted
[  319.799643] ------------------------------------------------------
[  319.799644] qemu-system-s39/14220 is trying to acquire lock:
[  319.799646] 00000000b30c0b50 (&kvm->lock){+.+.}-{3:3}, at: kvm_s390_set_tod_clock+0x36/0x250
[  319.799659]
               but task is already holding lock:
[  319.799660] 00000000b5beda60 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x9a/0x958
[  319.799665]
               which lock already depends on the new lock.

[  319.799667]
               the existing dependency chain (in reverse order) is:
[  319.799668]
               -> #1 (&vcpu->mutex){+.+.}-{3:3}:
[  319.799671]        __mutex_lock+0x8a/0x798
[  319.799677]        mutex_lock_nested+0x32/0x40
[  319.799679]        kvm_arch_vm_ioctl+0x1902/0x2c58
[  319.799682]        kvm_vm_ioctl+0x5b0/0xa80
[  319.799685]        __s390x_sys_ioctl+0xbe/0x100
[  319.799688]        __do_syscall+0x1da/0x208
[  319.799689]        system_call+0x82/0xb0
[  319.799692]
               -> #0 (&kvm->lock){+.+.}-{3:3}:
[  319.799694]        __lock_acquire+0x1916/0x2e70
[  319.799699]        lock_acquire+0x164/0x388
[  319.799702]        __mutex_lock+0x8a/0x798
[  319.799757]        mutex_lock_nested+0x32/0x40
[  319.799759]        kvm_s390_set_tod_clock+0x36/0x250
[  319.799761]        kvm_s390_handle_b2+0x6cc/0x26f0
[  319.799764]        kvm_handle_sie_intercept+0x1fe/0xe98
[  319.799765]        kvm_arch_vcpu_ioctl_run+0xec8/0x1880
[  319.799768]        kvm_vcpu_ioctl+0x29e/0x958
[  319.799769]        __s390x_sys_ioctl+0xbe/0x100
[  319.799771]        __do_syscall+0x1da/0x208
[  319.799773]        system_call+0x82/0xb0
[  319.799774]
               other info that might help us debug this:

[  319.799776]  Possible unsafe locking scenario:

[  319.799777]        CPU0                    CPU1
[  319.799778]        ----                    ----
[  319.799779]   lock(&vcpu->mutex);
[  319.799780]                                lock(&kvm->lock);
[  319.799782]                                lock(&vcpu->mutex);
[  319.799783]   lock(&kvm->lock);
[  319.799784]
                *** DEADLOCK ***

[  319.799785] 2 locks held by qemu-system-s39/14220:
[  319.799787]  #0: 00000000b5beda60 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x9a/0x958
[  319.799791]  #1: 00000000b30c4588 (&kvm->srcu){....}-{0:0}, at: kvm_arch_vcpu_ioctl_run+0x6f2/0x1880
[  319.799796]
               stack backtrace:
[  319.799798] CPU: 5 PID: 14220 Comm: qemu-system-s39 Not tainted 5.17.0-rc5-08427-gfd14b6309198 #4661
[  319.799801] Hardware name: IBM 8561 T01 701 (LPAR)
[  319.799802] Call Trace:
[  319.799803]  [<000000020d7410de>] dump_stack_lvl+0x76/0x98
[  319.799808]  [<000000020cbbd268>] check_noncircular+0x140/0x160
[  319.799811]  [<000000020cbc0efe>] __lock_acquire+0x1916/0x2e70
[  319.799813]  [<000000020cbc2dbc>] lock_acquire+0x164/0x388
[  319.799816]  [<000000020d75013a>] __mutex_lock+0x8a/0x798
[  319.799818]  [<000000020d75087a>] mutex_lock_nested+0x32/0x40
[  319.799820]  [<000000020cb029a6>] kvm_s390_set_tod_clock+0x36/0x250
[  319.799823]  [<000000020cb14d14>] kvm_s390_handle_b2+0x6cc/0x26f0
[  319.799825]  [<000000020cb09b6e>] kvm_handle_sie_intercept+0x1fe/0xe98
[  319.799827]  [<000000020cb06c28>] kvm_arch_vcpu_ioctl_run+0xec8/0x1880
[  319.799829]  [<000000020caeddc6>] kvm_vcpu_ioctl+0x29e/0x958
[  319.799831]  [<000000020ce4e82e>] __s390x_sys_ioctl+0xbe/0x100
[  319.799833]  [<000000020d744a72>] __do_syscall+0x1da/0x208
[  319.799835]  [<000000020d757322>] system_call+0x82/0xb0
[  319.799836] INFO: lockdep is turned off.

Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2296b1ff1e02..b75ea3e57172 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2185,15 +2185,15 @@ static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
 	 * behind.
 	 * We want to return the first failure rc and rrc, though.
 	 */
+	kvm_s390_vcpu_block_all(kvm);
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		mutex_lock(&vcpu->mutex);
 		if (kvm_s390_pv_destroy_cpu(vcpu, &rc, &rrc) && !ret) {
 			*rcp = rc;
 			*rrcp = rrc;
 			ret = -EIO;
 		}
-		mutex_unlock(&vcpu->mutex);
 	}
+	kvm_s390_vcpu_unblock_all(kvm);
 	return ret;
 }
 
@@ -2205,13 +2205,13 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
 
 	struct kvm_vcpu *vcpu;
 
+	kvm_s390_vcpu_block_all(kvm);
 	kvm_for_each_vcpu(i, vcpu, kvm) {
-		mutex_lock(&vcpu->mutex);
 		r = kvm_s390_pv_create_cpu(vcpu, rc, rrc);
-		mutex_unlock(&vcpu->mutex);
 		if (r)
 			break;
 	}
+	kvm_s390_vcpu_unblock_all(kvm);
 	if (r)
 		kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
 	return r;
-- 
2.32.0

[PATCH v4 2/2] KVM: s390: pv: make use of ultravisor AIV support

[Michael Mueller]

This patch enables the ultravisor adapter interruption vitualization
support indicated by UV feature BIT_UV_FEAT_AIV. This allows ISC
interruption injection directly into the GISA IPM for PV kvm guests.

Hardware that does not support this feature will continue to use the
UV interruption interception method to deliver ISC interruptions to
PV kvm guests. For this purpose, the ECA_AIV bit for all guest cpus
will be cleared and the GISA will be disabled during PV CPU setup.

In addition a check in __inject_io() has been removed. That reduces the
required instructions for interruption handling for PV and traditional
kvm guests.

Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
---
 arch/s390/include/asm/uv.h |  1 +
 arch/s390/kvm/interrupt.c  | 54 +++++++++++++++++++++++++++++++++-----
 arch/s390/kvm/kvm-s390.c   | 11 +++++---
 arch/s390/kvm/kvm-s390.h   | 11 ++++++++
 4 files changed, 68 insertions(+), 9 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 86218382d29c..a2d376b8bce3 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -80,6 +80,7 @@ enum uv_cmds_inst {
 
 enum uv_feat_ind {
 	BIT_UV_FEAT_MISC = 0,
+	BIT_UV_FEAT_AIV = 1,
 };
 
 struct uv_cb_header {
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index db933c252dbc..c3b2c7650b48 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1901,13 +1901,12 @@ static int __inject_io(struct kvm *kvm, struct kvm_s390_interrupt_info *inti)
 	isc = int_word_to_isc(inti->io.io_int_word);
 
 	/*
-	 * Do not make use of gisa in protected mode. We do not use the lock
-	 * checking variant as this is just a performance optimization and we
-	 * do not hold the lock here. This is ok as the code will pick
-	 * interrupts from both "lists" for delivery.
+	 * We do not use the lock checking variant as this is just a
+	 * performance optimization and we do not hold the lock here.
+	 * This is ok as the code will pick interrupts from both "lists"
+	 * for delivery.
 	 */
-	if (!kvm_s390_pv_get_handle(kvm) &&
-	    gi->origin && inti->type & KVM_S390_INT_IO_AI_MASK) {
+	if (gi->origin && inti->type & KVM_S390_INT_IO_AI_MASK) {
 		VM_EVENT(kvm, 4, "%s isc %1u", "inject: I/O (AI/gisa)", isc);
 		gisa_set_ipm_gisc(gi->origin, isc);
 		kfree(inti);
@@ -3171,9 +3170,33 @@ void kvm_s390_gisa_init(struct kvm *kvm)
 	VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin);
 }
 
+void kvm_s390_gisa_enable(struct kvm *kvm)
+{
+	struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+	struct kvm_vcpu *vcpu;
+	unsigned long i;
+	u32 gisa_desc;
+
+	if (gi->origin)
+		return;
+	kvm_s390_gisa_init(kvm);
+	gisa_desc = kvm_s390_get_gisa_desc(kvm);
+	if (!gisa_desc)
+		return;
+	kvm_s390_vcpu_block_all(kvm);
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		vcpu->arch.sie_block->gd = gisa_desc;
+		vcpu->arch.sie_block->eca |= ECA_AIV;
+		VCPU_EVENT(vcpu, 3, "AIV gisa format-%u enabled for cpu %03u",
+			   vcpu->arch.sie_block->gd & 0x3, vcpu->vcpu_id);
+	}
+	kvm_s390_vcpu_unblock_all(kvm);
+}
+
 void kvm_s390_gisa_destroy(struct kvm *kvm)
 {
 	struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+	struct kvm_s390_gisa *gisa = gi->origin;
 
 	if (!gi->origin)
 		return;
@@ -3184,6 +3207,25 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
 		cpu_relax();
 	hrtimer_cancel(&gi->timer);
 	gi->origin = NULL;
+	VM_EVENT(kvm, 3, "gisa 0x%pK destroyed", gisa);
+}
+
+void kvm_s390_gisa_disable(struct kvm *kvm)
+{
+	struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+	struct kvm_vcpu *vcpu;
+	unsigned long i;
+
+	if (!gi->origin)
+		return;
+	kvm_s390_vcpu_block_all(kvm);
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		vcpu->arch.sie_block->eca &= ~ECA_AIV;
+		vcpu->arch.sie_block->gd = 0U;
+		VCPU_EVENT(vcpu, 3, "AIV disabled for cpu %03u", vcpu->vcpu_id);
+	}
+	kvm_s390_vcpu_unblock_all(kvm);
+	kvm_s390_gisa_destroy(kvm);
 }
 
 /**
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b75ea3e57172..e2827c0ed642 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2194,6 +2194,9 @@ static int kvm_s390_cpus_from_pv(struct kvm *kvm, u16 *rcp, u16 *rrcp)
 		}
 	}
 	kvm_s390_vcpu_unblock_all(kvm);
+	/* Ensure that we re-enable gisa if the non-PV guest used it but the PV guest did not. */
+	if (use_gisa)
+		kvm_s390_gisa_enable(kvm);
 	return ret;
 }
 
@@ -2205,6 +2208,10 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
 
 	struct kvm_vcpu *vcpu;
 
+	/* Disable the GISA if the ultravisor does not support AIV. */
+	if (!test_bit_inv(BIT_UV_FEAT_AIV, &uv_info.uv_feature_indications))
+		kvm_s390_gisa_disable(kvm);
+
 	kvm_s390_vcpu_block_all(kvm);
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		r = kvm_s390_pv_create_cpu(vcpu, rc, rrc);
@@ -3263,9 +3270,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.sie_block->icpua = vcpu->vcpu_id;
 	spin_lock_init(&vcpu->arch.local_int.lock);
-	vcpu->arch.sie_block->gd = (u32)(u64)vcpu->kvm->arch.gisa_int.origin;
-	if (vcpu->arch.sie_block->gd && sclp.has_gisaf)
-		vcpu->arch.sie_block->gd |= GISA_FORMAT1;
+	vcpu->arch.sie_block->gd = kvm_s390_get_gisa_desc(vcpu->kvm);
 	seqcount_init(&vcpu->arch.cputm_seqcount);
 
 	vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 098831e815e6..4ba8fc30d87a 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -231,6 +231,15 @@ static inline unsigned long kvm_s390_get_gfn_end(struct kvm_memslots *slots)
 	return ms->base_gfn + ms->npages;
 }
 
+static inline u32 kvm_s390_get_gisa_desc(struct kvm *kvm)
+{
+	u32 gd = (u32)(u64)kvm->arch.gisa_int.origin;
+
+	if (gd && sclp.has_gisaf)
+		gd |= GISA_FORMAT1;
+	return gd;
+}
+
 /* implemented in pv.c */
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
 int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
@@ -450,6 +459,8 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu,
 void kvm_s390_gisa_init(struct kvm *kvm);
 void kvm_s390_gisa_clear(struct kvm *kvm);
 void kvm_s390_gisa_destroy(struct kvm *kvm);
+void kvm_s390_gisa_disable(struct kvm *kvm);
+void kvm_s390_gisa_enable(struct kvm *kvm);
 int kvm_s390_gib_init(u8 nisc);
 void kvm_s390_gib_destroy(void);
 
-- 
2.32.0

Re: [PATCH v4 0/2] KVM: s390: make use of ultravisor AIV support

[Michael Mueller]

On 23.02.22 11:19, Michael Mueller wrote:
> This patch enables the ultravisor adapter interruption vitualization
> support.
> 
> Changes in v4:
> - All vcpus are pulled out of SIE and disbled before the control
>    blocks are changed to disable/enable the gisa and re-enabled
>    afterwards instead of taking the vcpu specific lock.


Christian,

I'm pulling back this v4 and ask for v3 to be re-applied as it turned
out that the described issue is related to kvm_s390_set_tod_clock()
being called in SIE intercepted context.

> 
> Changes in v3:
> - cache and test GISA descriptor only once in kvm_s390_gisa_enable()
> - modified some comments
> - removed some whitespace issues
> 
> Changes in v2:
> - moved GISA disable into "put CPUs in PV mode" routine
> - moved GISA enable into "pull CPUs out of PV mode" routine
> 
> [1] https://lore.kernel.org/lkml/ae7c65d8-f632-a7f4-926a-50b9660673a1@linux.ibm.com/T/#mcb67699bf458ba7482f6b7529afe589d1dbb5930
> [2] https://lore.kernel.org/all/20220208165310.3905815-1-mimu@linux.ibm.com/
> [3] https://lore.kernel.org/all/20220209152217.1793281-2-mimu@linux.ibm.com/
> 
> Michael Mueller (2):
>    KVM: s390: pv: pull all vcpus out of SIE before converting to/from pv
>      vcpu
>    KVM: s390: pv: make use of ultravisor AIV support
> 
>   arch/s390/include/asm/uv.h |  1 +
>   arch/s390/kvm/interrupt.c  | 54 +++++++++++++++++++++++++++++++++-----
>   arch/s390/kvm/kvm-s390.c   | 19 +++++++++-----
>   arch/s390/kvm/kvm-s390.h   | 11 ++++++++
>   4 files changed, 72 insertions(+), 13 deletions(-)
>