[PATCH v4 0/4] iommu/s390: add support for IOMMU passthrough

[PATCH v4 0/4] iommu/s390: add support for IOMMU passthrough

[Matthew Rosato]

This series introduces the ability for certain devices on s390 to bypass
a layer of IOMMU via the iommu.passthrough=1 option.  In order to enable
this, the concept of an identity domain is added to s390-iommu.  On s390,
IOMMU passthrough is only allowed if indicated via a special bit in s390
CLP data for the associated device group, otherwise we must fall back to
dma-iommu.

Changes for v4:
- Additional patch to handle IOAT registration within s390-iommu.  This
  fixes an issue with re-registration of identity domain during events
  like zpci_hot_reset_device
- Fixup page alignment for bus_dma_region setup
- Dropped a few review/test tags due to above changes

Changes for v3:
- Rebase onto 6.13
- fixed bus_dma_region size (Niklas) 

Changes for v2:
- Remove ARCH_HAS_PHYS_TO_DMA, use bus_dma_region
- Remove use of def_domain_type, use 1 of 2 ops chosen at init

Matthew Rosato (4):
  s390/pci: check for relaxed translation capability
  s390/pci: store DMA offset in bus_dma_region
  iommu/s390: handle IOAT registration based on domain
  iommu/s390: implement iommu passthrough via identity domain

 arch/s390/include/asm/pci.h     |   4 +-
 arch/s390/include/asm/pci_clp.h |   4 +-
 arch/s390/kvm/pci.c             |  17 +---
 arch/s390/pci/pci.c             |  35 ++++----
 arch/s390/pci/pci_bus.c         |  18 +++++
 arch/s390/pci/pci_clp.c         |   1 +
 arch/s390/pci/pci_sysfs.c       |  11 +--
 drivers/iommu/s390-iommu.c      | 138 ++++++++++++++++++++++++++------
 8 files changed, 161 insertions(+), 67 deletions(-)

-- 
2.48.1

[PATCH v4 1/4] s390/pci: check for relaxed translation capability

[Matthew Rosato]

For each zdev, record whether or not CLP indicates relaxed translation
capability for the associated device group.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 arch/s390/include/asm/pci.h     | 2 +-
 arch/s390/include/asm/pci_clp.h | 4 +++-
 arch/s390/pci/pci_clp.c         | 1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 474e1f8d1d3c..8fe4c7a72c0b 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -144,7 +144,7 @@ struct zpci_dev {
 	u8		util_str_avail	: 1;
 	u8		irqs_registered	: 1;
 	u8		tid_avail	: 1;
-	u8		reserved	: 1;
+	u8		rtr_avail	: 1; /* Relaxed translation allowed */
 	unsigned int	devfn;		/* DEVFN part of the RID*/
 
 	u8 pfip[CLP_PFIP_NR_SEGMENTS];	/* pci function internal path */
diff --git a/arch/s390/include/asm/pci_clp.h b/arch/s390/include/asm/pci_clp.h
index 3fff2f7095c8..7ebff39c84b3 100644
--- a/arch/s390/include/asm/pci_clp.h
+++ b/arch/s390/include/asm/pci_clp.h
@@ -156,7 +156,9 @@ struct clp_rsp_query_pci_grp {
 	u16			:  4;
 	u16 noi			: 12;	/* number of interrupts */
 	u8 version;
-	u8			:  6;
+	u8			:  2;
+	u8 rtr			:  1;	/* Relaxed translation requirement */
+	u8			:  3;
 	u8 frame		:  1;
 	u8 refresh		:  1;	/* TLB refresh mode */
 	u16			:  3;
diff --git a/arch/s390/pci/pci_clp.c b/arch/s390/pci/pci_clp.c
index 14bf7e8d06b7..27248686e588 100644
--- a/arch/s390/pci/pci_clp.c
+++ b/arch/s390/pci/pci_clp.c
@@ -112,6 +112,7 @@ static void clp_store_query_pci_fngrp(struct zpci_dev *zdev,
 	zdev->version = response->version;
 	zdev->maxstbl = response->maxstbl;
 	zdev->dtsm = response->dtsm;
+	zdev->rtr_avail = response->rtr;
 
 	switch (response->version) {
 	case 1:
-- 
2.48.1

[PATCH v4 2/4] s390/pci: store DMA offset in bus_dma_region

[Matthew Rosato]

PCI devices on s390 have a DMA offset that is reported via CLP.  In
preparation for allowing identity domains, setup the bus_dma_region
for all PCI devices using the reported CLP value.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 arch/s390/pci/pci_bus.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
index 857afbc4828f..b5c35b8e47a4 100644
--- a/arch/s390/pci/pci_bus.c
+++ b/arch/s390/pci/pci_bus.c
@@ -19,6 +19,7 @@
 #include <linux/jump_label.h>
 #include <linux/pci.h>
 #include <linux/printk.h>
+#include <linux/dma-direct.h>
 
 #include <asm/pci_clp.h>
 #include <asm/pci_dma.h>
@@ -283,10 +284,27 @@ static struct zpci_bus *zpci_bus_alloc(int topo, bool topo_is_tid)
 	return zbus;
 }
 
+static void pci_dma_range_setup(struct pci_dev *pdev)
+{
+	struct zpci_dev *zdev = to_zpci(pdev);
+	struct bus_dma_region *map;
+
+	map = kzalloc(sizeof(*map), GFP_KERNEL);
+	if (!map)
+		return;
+
+	map->cpu_start = 0;
+	map->dma_start = PAGE_ALIGN(zdev->start_dma);
+	map->size = max(PAGE_ALIGN_DOWN(zdev->end_dma + 1) - map->dma_start, 0);
+	pdev->dev.dma_range_map = map;
+}
+
 void pcibios_bus_add_device(struct pci_dev *pdev)
 {
 	struct zpci_dev *zdev = to_zpci(pdev);
 
+	pci_dma_range_setup(pdev);
+
 	/*
 	 * With pdev->no_vf_scan the common PCI probing code does not
 	 * perform PF/VF linking.
-- 
2.48.1

Re: [PATCH v4 2/4] s390/pci: store DMA offset in bus_dma_region

[Niklas Schnelle]

On Fri, 2025-02-07 at 15:53 -0500, Matthew Rosato wrote:
> PCI devices on s390 have a DMA offset that is reported via CLP.  In
> preparation for allowing identity domains, setup the bus_dma_region
> for all PCI devices using the reported CLP value.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  arch/s390/pci/pci_bus.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
> index 857afbc4828f..b5c35b8e47a4 100644
> --- a/arch/s390/pci/pci_bus.c
> +++ b/arch/s390/pci/pci_bus.c
> @@ -19,6 +19,7 @@
>  #include <linux/jump_label.h>
>  #include <linux/pci.h>
>  #include <linux/printk.h>
> +#include <linux/dma-direct.h>
>  
>  #include <asm/pci_clp.h>
>  #include <asm/pci_dma.h>
> @@ -283,10 +284,27 @@ static struct zpci_bus *zpci_bus_alloc(int topo, bool topo_is_tid)
>  	return zbus;
>  }
>  
> +static void pci_dma_range_setup(struct pci_dev *pdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(pdev);
> +	struct bus_dma_region *map;
> +
> +	map = kzalloc(sizeof(*map), GFP_KERNEL);
> +	if (!map)
> +		return;
> +
> +	map->cpu_start = 0;
> +	map->dma_start = PAGE_ALIGN(zdev->start_dma);
> +	map->size = max(PAGE_ALIGN_DOWN(zdev->end_dma + 1) - map->dma_start, 0);

Ugh, this is my fault as I suggested it, but this max() doesn't work
here. The zdev->end_dma is unsigned and so is map->dma_start so if the
former is smaller underflow will occur and the max() won't save us.
It's largely a theoretical issue since zdev->end_dma + 1 should always
be larger than zdev->start_dma, but now the max() looks like we thought
of that, but then it doesn't work.

If we handle it maybe just go with:

aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
if (aligned_end >= map->dma_start)
     map->size = aligned_end - map->dma_start;
else
     map->size = 0;


> +	pdev->dev.dma_range_map = map;
> +}
> +
>  void pcibios_bus_add_device(struct pci_dev *pdev)
>  {
>  	struct zpci_dev *zdev = to_zpci(pdev);
>  
> +	pci_dma_range_setup(pdev);
> +
>  	/*
>  	 * With pdev->no_vf_scan the common PCI probing code does not
>  	 * perform PF/VF linking.

Re: [PATCH v4 2/4] s390/pci: store DMA offset in bus_dma_region

[Matthew Rosato]

>> +static void pci_dma_range_setup(struct pci_dev *pdev)
>> +{
>> +	struct zpci_dev *zdev = to_zpci(pdev);
>> +	struct bus_dma_region *map;
>> +
>> +	map = kzalloc(sizeof(*map), GFP_KERNEL);
>> +	if (!map)
>> +		return;
>> +
>> +	map->cpu_start = 0;
>> +	map->dma_start = PAGE_ALIGN(zdev->start_dma);
>> +	map->size = max(PAGE_ALIGN_DOWN(zdev->end_dma + 1) - map->dma_start, 0);
> 
> Ugh, this is my fault as I suggested it, but this max() doesn't work
> here. The zdev->end_dma is unsigned and so is map->dma_start so if the
> former is smaller underflow will occur and the max() won't save us.
> It's largely a theoretical issue since zdev->end_dma + 1 should always
> be larger than zdev->start_dma, but now the max() looks like we thought
> of that, but then it doesn't work.
> 
> If we handle it maybe just go with:
> 
> aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
> if (aligned_end >= map->dma_start)
>      map->size = aligned_end - map->dma_start;
> else
>      map->size = 0;
> 


Given that it's not really something that's supposed to happen, would it make sense then to add a 

WARN_ON_ONCE(map->size == 0);

At the end of this?

Re: [PATCH v4 2/4] s390/pci: store DMA offset in bus_dma_region

[Niklas Schnelle]

On Wed, 2025-02-12 at 10:23 -0500, Matthew Rosato wrote:
> > > +static void pci_dma_range_setup(struct pci_dev *pdev)
> > > +{
> > > +	struct zpci_dev *zdev = to_zpci(pdev);
> > > +	struct bus_dma_region *map;
> > > +
> > > +	map = kzalloc(sizeof(*map), GFP_KERNEL);
> > > +	if (!map)
> > > +		return;
> > > +
> > > +	map->cpu_start = 0;
> > > +	map->dma_start = PAGE_ALIGN(zdev->start_dma);
> > > +	map->size = max(PAGE_ALIGN_DOWN(zdev->end_dma + 1) - map->dma_start, 0);
> > 
> > Ugh, this is my fault as I suggested it, but this max() doesn't work
> > here. The zdev->end_dma is unsigned and so is map->dma_start so if the
> > former is smaller underflow will occur and the max() won't save us.
> > It's largely a theoretical issue since zdev->end_dma + 1 should always
> > be larger than zdev->start_dma, but now the max() looks like we thought
> > of that, but then it doesn't work.
> > 
> > If we handle it maybe just go with:
> > 
> > aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
> > if (aligned_end >= map->dma_start)
> >      map->size = aligned_end - map->dma_start;
> > else
> >      map->size = 0;
> > 
> 
> 
> Given that it's not really something that's supposed to happen, would it make sense then to add a 
> 
> WARN_ON_ONCE(map->size == 0);
> 
> At the end of this?


Yes that makes sense to me

[PATCH v4 3/4] iommu/s390: handle IOAT registration based on domain

[Matthew Rosato]

At this point, the dma_table is really a property of the s390-iommu
domain.  Rather than checking its contents elsewhere in the codebase,
move the code that registers the table with firmware into
s390-iommu and make a decision what to register with firmware based
upon the type of domain in use for the device in question.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 arch/s390/include/asm/pci.h |  2 ++
 arch/s390/kvm/pci.c         | 17 ++-------------
 arch/s390/pci/pci.c         | 35 +++++++++++++++++-------------
 arch/s390/pci/pci_sysfs.c   | 11 +---------
 drivers/iommu/s390-iommu.c  | 43 +++++++++++++++++++++++++++++++++++--
 5 files changed, 66 insertions(+), 42 deletions(-)

diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 8fe4c7a72c0b..7cc6a7cc66e7 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -217,6 +217,7 @@ extern struct airq_iv *zpci_aif_sbv;
 struct zpci_dev *zpci_create_device(u32 fid, u32 fh, enum zpci_state state);
 int zpci_add_device(struct zpci_dev *zdev);
 int zpci_enable_device(struct zpci_dev *);
+int zpci_reenable_device(struct zpci_dev *zdev);
 int zpci_disable_device(struct zpci_dev *);
 int zpci_scan_configured_device(struct zpci_dev *zdev, u32 fh);
 int zpci_deconfigure_device(struct zpci_dev *zdev);
@@ -245,6 +246,7 @@ void update_uid_checking(bool new);
 /* IOMMU Interface */
 int zpci_init_iommu(struct zpci_dev *zdev);
 void zpci_destroy_iommu(struct zpci_dev *zdev);
+int zpci_iommu_register_ioat(struct zpci_dev *zdev, u8 *status);
 
 #ifdef CONFIG_PCI
 static inline bool zpci_use_mio(struct zpci_dev *zdev)
diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 9b9e7fdd5380..8c40154ff50f 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -433,7 +433,6 @@ static void kvm_s390_pci_dev_release(struct zpci_dev *zdev)
 static int kvm_s390_pci_register_kvm(void *opaque, struct kvm *kvm)
 {
 	struct zpci_dev *zdev = opaque;
-	u8 status;
 	int rc;
 
 	if (!zdev)
@@ -480,13 +479,7 @@ static int kvm_s390_pci_register_kvm(void *opaque, struct kvm *kvm)
 	 */
 	zdev->gisa = (u32)virt_to_phys(&kvm->arch.sie_page2->gisa);
 
-	rc = zpci_enable_device(zdev);
-	if (rc)
-		goto clear_gisa;
-
-	/* Re-register the IOMMU that was already created */
-	rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-				virt_to_phys(zdev->dma_table), &status);
+	rc = zpci_reenable_device(zdev);
 	if (rc)
 		goto clear_gisa;
 
@@ -516,7 +509,6 @@ static void kvm_s390_pci_unregister_kvm(void *opaque)
 {
 	struct zpci_dev *zdev = opaque;
 	struct kvm *kvm;
-	u8 status;
 
 	if (!zdev)
 		return;
@@ -550,12 +542,7 @@ static void kvm_s390_pci_unregister_kvm(void *opaque)
 			goto out;
 	}
 
-	if (zpci_enable_device(zdev))
-		goto out;
-
-	/* Re-register the IOMMU that was already created */
-	zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-			   virt_to_phys(zdev->dma_table), &status);
+	zpci_reenable_device(zdev);
 
 out:
 	spin_lock(&kvm->arch.kzdev_list_lock);
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 88f72745fa59..fa879351efb5 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -124,14 +124,13 @@ int zpci_register_ioat(struct zpci_dev *zdev, u8 dmaas,
 	struct zpci_fib fib = {0};
 	u8 cc;
 
-	WARN_ON_ONCE(iota & 0x3fff);
 	fib.pba = base;
 	/* Work around off by one in ISM virt device */
 	if (zdev->pft == PCI_FUNC_TYPE_ISM && limit > base)
 		fib.pal = limit + (1 << 12);
 	else
 		fib.pal = limit;
-	fib.iota = iota | ZPCI_IOTA_RTTO_FLAG;
+	fib.iota = iota;
 	fib.gd = zdev->gisa;
 	cc = zpci_mod_fc(req, &fib, status);
 	if (cc)
@@ -690,6 +689,23 @@ int zpci_enable_device(struct zpci_dev *zdev)
 }
 EXPORT_SYMBOL_GPL(zpci_enable_device);
 
+int zpci_reenable_device(struct zpci_dev *zdev)
+{
+	u8 status;
+	int rc;
+
+	rc = zpci_enable_device(zdev);
+	if (rc)
+		return rc;
+
+	rc = zpci_iommu_register_ioat(zdev, &status);
+	if (rc)
+		zpci_disable_device(zdev);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(zpci_reenable_device);
+
 int zpci_disable_device(struct zpci_dev *zdev)
 {
 	u32 fh = zdev->fh;
@@ -739,7 +755,6 @@ EXPORT_SYMBOL_GPL(zpci_disable_device);
  */
 int zpci_hot_reset_device(struct zpci_dev *zdev)
 {
-	u8 status;
 	int rc;
 
 	lockdep_assert_held(&zdev->state_lock);
@@ -758,19 +773,9 @@ int zpci_hot_reset_device(struct zpci_dev *zdev)
 			return rc;
 	}
 
-	rc = zpci_enable_device(zdev);
-	if (rc)
-		return rc;
-
-	if (zdev->dma_table)
-		rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-					virt_to_phys(zdev->dma_table), &status);
-	if (rc) {
-		zpci_disable_device(zdev);
-		return rc;
-	}
+	rc = zpci_reenable_device(zdev);
 
-	return 0;
+	return rc;
 }
 
 /**
diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c
index 2de1ea6c3a8c..0ecad08e1b1e 100644
--- a/arch/s390/pci/pci_sysfs.c
+++ b/arch/s390/pci/pci_sysfs.c
@@ -52,7 +52,6 @@ static DEVICE_ATTR_RO(mio_enabled);
 
 static int _do_recover(struct pci_dev *pdev, struct zpci_dev *zdev)
 {
-	u8 status;
 	int ret;
 
 	pci_stop_and_remove_bus_device(pdev);
@@ -70,16 +69,8 @@ static int _do_recover(struct pci_dev *pdev, struct zpci_dev *zdev)
 			return ret;
 	}
 
-	ret = zpci_enable_device(zdev);
-	if (ret)
-		return ret;
+	ret = zpci_reenable_device(zdev);
 
-	if (zdev->dma_table) {
-		ret = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-					 virt_to_phys(zdev->dma_table), &status);
-		if (ret)
-			zpci_disable_device(zdev);
-	}
 	return ret;
 }
 
diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index fbdeded3d48b..007ccfdad495 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -381,6 +381,46 @@ static void zdev_s390_domain_update(struct zpci_dev *zdev,
 	spin_unlock_irqrestore(&zdev->dom_lock, flags);
 }
 
+static int s390_iommu_domain_reg_ioat(struct zpci_dev *zdev,
+				      struct iommu_domain *domain, u8 *status)
+{
+	struct s390_domain *s390_domain;
+	int rc = 0;
+	u64 iota;
+
+	switch (domain->type) {
+	case IOMMU_DOMAIN_IDENTITY:
+		rc = zpci_register_ioat(zdev, 0, zdev->start_dma,
+					zdev->end_dma, 0, status);
+		break;
+	case IOMMU_DOMAIN_BLOCKED:
+		/* Nothing to do in this case */
+		break;
+	default:
+		s390_domain = to_s390_domain(domain);
+		iota = virt_to_phys(s390_domain->dma_table) |
+		       ZPCI_IOTA_RTTO_FLAG;
+		rc = zpci_register_ioat(zdev, 0, zdev->start_dma,
+					zdev->end_dma, iota, status);
+	}
+
+	return rc;
+}
+
+int zpci_iommu_register_ioat(struct zpci_dev *zdev, u8 *status)
+{
+	unsigned long flags;
+	int rc;
+
+	spin_lock_irqsave(&zdev->dom_lock, flags);
+
+	rc = s390_iommu_domain_reg_ioat(zdev, zdev->s390_domain, status);
+
+	spin_unlock_irqrestore(&zdev->dom_lock, flags);
+
+	return rc;
+}
+
 static int blocking_domain_attach_device(struct iommu_domain *domain,
 					 struct device *dev)
 {
@@ -422,8 +462,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 	blocking_domain_attach_device(&blocking_domain, dev);
 
 	/* If we fail now DMA remains blocked via blocking domain */
-	cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-				virt_to_phys(s390_domain->dma_table), &status);
+	cc = s390_iommu_domain_reg_ioat(zdev, domain, &status);
 	if (cc && status != ZPCI_PCI_ST_FUNC_NOT_AVAIL)
 		return -EIO;
 	zdev->dma_table = s390_domain->dma_table;
-- 
2.48.1

Re: [PATCH v4 3/4] iommu/s390: handle IOAT registration based on domain

[Niklas Schnelle]

On Fri, 2025-02-07 at 15:53 -0500, Matthew Rosato wrote:
> At this point, the dma_table is really a property of the s390-iommu
> domain.  Rather than checking its contents elsewhere in the codebase,
> move the code that registers the table with firmware into
> s390-iommu and make a decision what to register with firmware based
> upon the type of domain in use for the device in question.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  arch/s390/include/asm/pci.h |  2 ++
>  arch/s390/kvm/pci.c         | 17 ++-------------
>  arch/s390/pci/pci.c         | 35 +++++++++++++++++-------------
>  arch/s390/pci/pci_sysfs.c   | 11 +---------
>  drivers/iommu/s390-iommu.c  | 43 +++++++++++++++++++++++++++++++++++--
>  5 files changed, 66 insertions(+), 42 deletions(-)
> 
> 
--8<---
>  int zpci_hot_reset_device(struct zpci_dev *zdev)
>  {
> -	u8 status;
>  	int rc;
>  
>  	lockdep_assert_held(&zdev->state_lock);
> @@ -758,19 +773,9 @@ int zpci_hot_reset_device(struct zpci_dev *zdev)
>  			return rc;
>  	}
>  
> -	rc = zpci_enable_device(zdev);
> -	if (rc)
> -		return rc;
> -
> -	if (zdev->dma_table)
> -		rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> -					virt_to_phys(zdev->dma_table), &status);
> -	if (rc) {
> -		zpci_disable_device(zdev);
> -		return rc;
> -	}
> +	rc = zpci_reenable_device(zdev);
>  
> -	return 0;
> +	return rc;

I can confirm that this change to re-do the I/O address translation re-
registration fixes the below zpci_hot_reset_device() test which  in an
iommu.passthrough=1 guest was causing host IOMMU violations in v3:

# echo 'bus' > /sys/bus/pci/devices/2003\:00\:00.0/reset_method
# echo 1 > /sys/bus/pci/devices/2003\:00\:00.0/reset

>  }
> 
---8<---
>  
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index fbdeded3d48b..007ccfdad495 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -381,6 +381,46 @@ static void zdev_s390_domain_update(struct zpci_dev *zdev,
>  	spin_unlock_irqrestore(&zdev->dom_lock, flags);
>  }
>  
> +static int s390_iommu_domain_reg_ioat(struct zpci_dev *zdev,
> +				      struct iommu_domain *domain, u8 *status)
> +{
> +	struct s390_domain *s390_domain;
> +	int rc = 0;
> +	u64 iota;
> +
> +	switch (domain->type) {
> +	case IOMMU_DOMAIN_IDENTITY:
> +		rc = zpci_register_ioat(zdev, 0, zdev->start_dma,
> +					zdev->end_dma, 0, status);
> +		break;
> +	case IOMMU_DOMAIN_BLOCKED:
> +		/* Nothing to do in this case */
> +		break;
> +	default:
> +		s390_domain = to_s390_domain(domain);
> +		iota = virt_to_phys(s390_domain->dma_table) |
> +		       ZPCI_IOTA_RTTO_FLAG;
> +		rc = zpci_register_ioat(zdev, 0, zdev->start_dma,
> +					zdev->end_dma, iota, status);
> +	}
> +
> +	return rc;
> +}
> +
> +int zpci_iommu_register_ioat(struct zpci_dev *zdev, u8 *status)
> +{
> +	unsigned long flags;
> +	int rc;
> +
> +	spin_lock_irqsave(&zdev->dom_lock, flags);
> +
> +	rc = s390_iommu_domain_reg_ioat(zdev, zdev->s390_domain, status);
> +
> +	spin_unlock_irqrestore(&zdev->dom_lock, flags);
> +
> +	return rc;
> +}
> +
> 

I really like how this takes out more of the IOMMU details from non-
IOMMU code. Definitely an improvement in terms of on its own. As stated
above I tested that this fixes the one issue I stumbled over in testing
the previous version. So feel free to add:

Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>

[PATCH v4 4/4] iommu/s390: implement iommu passthrough via identity domain

[Matthew Rosato]

Enabled via the kernel command-line 'iommu.passthrough=1' option.

Introduce the concept of identity domains to s390-iommu, which relies on
the bus_dma_region to offset identity mappings to the start of the DMA
aperture advertized by CLP.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 drivers/iommu/s390-iommu.c | 95 +++++++++++++++++++++++++++++---------
 1 file changed, 72 insertions(+), 23 deletions(-)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 007ccfdad495..e1c76e0f9c2b 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -16,7 +16,7 @@
 
 #include "dma-iommu.h"
 
-static const struct iommu_ops s390_iommu_ops;
+static const struct iommu_ops s390_iommu_ops, s390_iommu_rtr_ops;
 
 static struct kmem_cache *dma_region_table_cache;
 static struct kmem_cache *dma_page_table_cache;
@@ -432,9 +432,11 @@ static int blocking_domain_attach_device(struct iommu_domain *domain,
 		return 0;
 
 	s390_domain = to_s390_domain(zdev->s390_domain);
-	spin_lock_irqsave(&s390_domain->list_lock, flags);
-	list_del_rcu(&zdev->iommu_list);
-	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+	if (zdev->dma_table) {
+		spin_lock_irqsave(&s390_domain->list_lock, flags);
+		list_del_rcu(&zdev->iommu_list);
+		spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+	}
 
 	zpci_unregister_ioat(zdev, 0);
 	zdev->dma_table = NULL;
@@ -762,7 +764,13 @@ int zpci_init_iommu(struct zpci_dev *zdev)
 	if (rc)
 		goto out_err;
 
-	rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops, NULL);
+	if (zdev->rtr_avail) {
+		rc = iommu_device_register(&zdev->iommu_dev,
+					   &s390_iommu_rtr_ops, NULL);
+	} else {
+		rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops,
+					   NULL);
+	}
 	if (rc)
 		goto out_sysfs;
 
@@ -826,6 +834,39 @@ static int __init s390_iommu_init(void)
 }
 subsys_initcall(s390_iommu_init);
 
+static int s390_attach_dev_identity(struct iommu_domain *domain,
+				    struct device *dev)
+{
+	struct zpci_dev *zdev = to_zpci_dev(dev);
+	u8 status;
+	int cc;
+
+	blocking_domain_attach_device(&blocking_domain, dev);
+
+	/* If we fail now DMA remains blocked via blocking domain */
+	cc = s390_iommu_domain_reg_ioat(zdev, domain, &status);
+
+	/*
+	 * If the device is undergoing error recovery the reset code
+	 * will re-establish the new domain.
+	 */
+	if (cc && status != ZPCI_PCI_ST_FUNC_NOT_AVAIL)
+		return -EIO;
+
+	zdev_s390_domain_update(zdev, domain);
+
+	return 0;
+}
+
+static const struct iommu_domain_ops s390_identity_ops = {
+	.attach_dev = s390_attach_dev_identity,
+};
+
+static struct iommu_domain s390_identity_domain = {
+	.type = IOMMU_DOMAIN_IDENTITY,
+	.ops = &s390_identity_ops,
+};
+
 static struct iommu_domain blocking_domain = {
 	.type = IOMMU_DOMAIN_BLOCKED,
 	.ops = &(const struct iommu_domain_ops) {
@@ -833,23 +874,31 @@ static struct iommu_domain blocking_domain = {
 	}
 };
 
-static const struct iommu_ops s390_iommu_ops = {
-	.blocked_domain		= &blocking_domain,
-	.release_domain		= &blocking_domain,
-	.capable = s390_iommu_capable,
-	.domain_alloc_paging = s390_domain_alloc_paging,
-	.probe_device = s390_iommu_probe_device,
-	.device_group = generic_device_group,
-	.pgsize_bitmap = SZ_4K,
-	.get_resv_regions = s390_iommu_get_resv_regions,
-	.default_domain_ops = &(const struct iommu_domain_ops) {
-		.attach_dev	= s390_iommu_attach_device,
-		.map_pages	= s390_iommu_map_pages,
-		.unmap_pages	= s390_iommu_unmap_pages,
-		.flush_iotlb_all = s390_iommu_flush_iotlb_all,
-		.iotlb_sync      = s390_iommu_iotlb_sync,
-		.iotlb_sync_map  = s390_iommu_iotlb_sync_map,
-		.iova_to_phys	= s390_iommu_iova_to_phys,
-		.free		= s390_domain_free,
+#define S390_IOMMU_COMMON_OPS() \
+	.blocked_domain		= &blocking_domain, \
+	.release_domain		= &blocking_domain, \
+	.capable = s390_iommu_capable, \
+	.domain_alloc_paging = s390_domain_alloc_paging, \
+	.probe_device = s390_iommu_probe_device, \
+	.device_group = generic_device_group, \
+	.pgsize_bitmap = SZ_4K, \
+	.get_resv_regions = s390_iommu_get_resv_regions, \
+	.default_domain_ops = &(const struct iommu_domain_ops) { \
+		.attach_dev	= s390_iommu_attach_device, \
+		.map_pages	= s390_iommu_map_pages, \
+		.unmap_pages	= s390_iommu_unmap_pages, \
+		.flush_iotlb_all = s390_iommu_flush_iotlb_all, \
+		.iotlb_sync      = s390_iommu_iotlb_sync, \
+		.iotlb_sync_map  = s390_iommu_iotlb_sync_map, \
+		.iova_to_phys	= s390_iommu_iova_to_phys, \
+		.free		= s390_domain_free, \
 	}
+
+static const struct iommu_ops s390_iommu_ops = {
+	S390_IOMMU_COMMON_OPS()
+};
+
+static const struct iommu_ops s390_iommu_rtr_ops = {
+	.identity_domain	= &s390_identity_domain,
+	S390_IOMMU_COMMON_OPS()
 };
-- 
2.48.1

Re: [PATCH v4 4/4] iommu/s390: implement iommu passthrough via identity domain

[Niklas Schnelle]

On Fri, 2025-02-07 at 15:53 -0500, Matthew Rosato wrote:
> Enabled via the kernel command-line 'iommu.passthrough=1' option.
> 
> Introduce the concept of identity domains to s390-iommu, which relies on
> the bus_dma_region to offset identity mappings to the start of the DMA
> aperture advertized by CLP.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>  drivers/iommu/s390-iommu.c | 95 +++++++++++++++++++++++++++++---------
>  1 file changed, 72 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> index 007ccfdad495..e1c76e0f9c2b 100644
> --- a/drivers/iommu/s390-iommu.c
> +++ b/drivers/iommu/s390-iommu.c
> @@ -16,7 +16,7 @@
>  
>  #include "dma-iommu.h"
>  
> -static const struct iommu_ops s390_iommu_ops;
> +static const struct iommu_ops s390_iommu_ops, s390_iommu_rtr_ops;
>  
>  static struct kmem_cache *dma_region_table_cache;
>  static struct kmem_cache *dma_page_table_cache;
> @@ -432,9 +432,11 @@ static int blocking_domain_attach_device(struct iommu_domain *domain,
>  		return 0;
>  
>  	s390_domain = to_s390_domain(zdev->s390_domain);
> -	spin_lock_irqsave(&s390_domain->list_lock, flags);
> -	list_del_rcu(&zdev->iommu_list);
> -	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> +	if (zdev->dma_table) {
> +		spin_lock_irqsave(&s390_domain->list_lock, flags);
> +		list_del_rcu(&zdev->iommu_list);
> +		spin_unlock_irqrestore(&s390_domain->list_lock, flags);
> +	}
>  
>  	zpci_unregister_ioat(zdev, 0);
>  	zdev->dma_table = NULL;
> @@ -762,7 +764,13 @@ int zpci_init_iommu(struct zpci_dev *zdev)
>  	if (rc)
>  		goto out_err;
>  
> -	rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops, NULL);
> +	if (zdev->rtr_avail) {
> +		rc = iommu_device_register(&zdev->iommu_dev,
> +					   &s390_iommu_rtr_ops, NULL);
> +	} else {
> +		rc = iommu_device_register(&zdev->iommu_dev, &s390_iommu_ops,
> +					   NULL);
> +	}
>  	if (rc)
>  		goto out_sysfs;
>  
> @@ -826,6 +834,39 @@ static int __init s390_iommu_init(void)
>  }
>  subsys_initcall(s390_iommu_init);
>  
> +static int s390_attach_dev_identity(struct iommu_domain *domain,
> +				    struct device *dev)
> +{
> +	struct zpci_dev *zdev = to_zpci_dev(dev);
> +	u8 status;
> +	int cc;
> +
> +	blocking_domain_attach_device(&blocking_domain, dev);
> +
> +	/* If we fail now DMA remains blocked via blocking domain */
> +	cc = s390_iommu_domain_reg_ioat(zdev, domain, &status);
> +
> +	/*
> +	 * If the device is undergoing error recovery the reset code
> +	 * will re-establish the new domain.
> +	 */
> +	if (cc && status != ZPCI_PCI_ST_FUNC_NOT_AVAIL)
> +		return -EIO;
> +
> +	zdev_s390_domain_update(zdev, domain);
> +
> +	return 0;
> +}
> +
> +static const struct iommu_domain_ops s390_identity_ops = {
> +	.attach_dev = s390_attach_dev_identity,
> +};
> +
> +static struct iommu_domain s390_identity_domain = {
> +	.type = IOMMU_DOMAIN_IDENTITY,
> +	.ops = &s390_identity_ops,
> +};
> +
>  static struct iommu_domain blocking_domain = {
>  	.type = IOMMU_DOMAIN_BLOCKED,
>  	.ops = &(const struct iommu_domain_ops) {
> @@ -833,23 +874,31 @@ static struct iommu_domain blocking_domain = {
>  	}
>  };
>  
> -static const struct iommu_ops s390_iommu_ops = {
> -	.blocked_domain		= &blocking_domain,
> -	.release_domain		= &blocking_domain,
> -	.capable = s390_iommu_capable,
> -	.domain_alloc_paging = s390_domain_alloc_paging,
> -	.probe_device = s390_iommu_probe_device,
> -	.device_group = generic_device_group,
> -	.pgsize_bitmap = SZ_4K,
> -	.get_resv_regions = s390_iommu_get_resv_regions,
> -	.default_domain_ops = &(const struct iommu_domain_ops) {
> -		.attach_dev	= s390_iommu_attach_device,
> -		.map_pages	= s390_iommu_map_pages,
> -		.unmap_pages	= s390_iommu_unmap_pages,
> -		.flush_iotlb_all = s390_iommu_flush_iotlb_all,
> -		.iotlb_sync      = s390_iommu_iotlb_sync,
> -		.iotlb_sync_map  = s390_iommu_iotlb_sync_map,
> -		.iova_to_phys	= s390_iommu_iova_to_phys,
> -		.free		= s390_domain_free,
> +#define S390_IOMMU_COMMON_OPS() \
> +	.blocked_domain		= &blocking_domain, \
> +	.release_domain		= &blocking_domain, \
> +	.capable = s390_iommu_capable, \
> +	.domain_alloc_paging = s390_domain_alloc_paging, \
> +	.probe_device = s390_iommu_probe_device, \
> +	.device_group = generic_device_group, \
> +	.pgsize_bitmap = SZ_4K, \
> +	.get_resv_regions = s390_iommu_get_resv_regions, \
> +	.default_domain_ops = &(const struct iommu_domain_ops) { \
> +		.attach_dev	= s390_iommu_attach_device, \
> +		.map_pages	= s390_iommu_map_pages, \
> +		.unmap_pages	= s390_iommu_unmap_pages, \
> +		.flush_iotlb_all = s390_iommu_flush_iotlb_all, \
> +		.iotlb_sync      = s390_iommu_iotlb_sync, \
> +		.iotlb_sync_map  = s390_iommu_iotlb_sync_map, \
> +		.iova_to_phys	= s390_iommu_iova_to_phys, \
> +		.free		= s390_domain_free, \
>  	}
> +
> +static const struct iommu_ops s390_iommu_ops = {
> +	S390_IOMMU_COMMON_OPS()
> +};
> +
> +static const struct iommu_ops s390_iommu_rtr_ops = {
> +	.identity_domain	= &s390_identity_domain,
> +	S390_IOMMU_COMMON_OPS()
>  };

Looks good to me here and worked well in my tests too. Thank you!

Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>