Re: [PATCH v2 20/30] KVM: s390: pci: provide routines for enabling/disabling IOAT assist

[Pierre Morel <pmorel@linux.ibm.com>]

On 1/14/22 21:31, Matthew Rosato wrote:
> These routines will be wired into the vfio_pci_zdev ioctl handlers to
> respond to requests to enable / disable a device for PCI I/O Address
> Translation assistance.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>   arch/s390/include/asm/kvm_pci.h |  15 ++++
>   arch/s390/include/asm/pci_dma.h |   2 +
>   arch/s390/kvm/pci.c             | 139 ++++++++++++++++++++++++++++++++
>   arch/s390/kvm/pci.h             |   2 +
>   4 files changed, 158 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index 01fe14fffd7a..770849f13a70 100644
> --- a/arch/s390/include/asm/kvm_pci.h
> +++ b/arch/s390/include/asm/kvm_pci.h
> @@ -16,11 +16,21 @@
>   #include <linux/kvm_host.h>
>   #include <linux/kvm.h>
>   #include <linux/pci.h>
> +#include <linux/mutex.h>
>   #include <asm/pci_insn.h>
> +#include <asm/pci_dma.h>
> +
> +struct kvm_zdev_ioat {
> +	unsigned long *head[ZPCI_TABLE_PAGES];
> +	unsigned long **seg;
> +	unsigned long ***pt;
> +	struct mutex lock;

Can we please rename the mutex ioat_lock to have a unique name easy to 
follow for maintenance.
Can you please add a description about when the lock should be used?

> +};
>   
>   struct kvm_zdev {
>   	struct zpci_dev *zdev;
>   	struct kvm *kvm;
> +	struct kvm_zdev_ioat ioat;
>   	struct zpci_fib fib;
>   };
>   
> @@ -33,6 +43,11 @@ int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
>   			    bool assist);
>   int kvm_s390_pci_aif_disable(struct zpci_dev *zdev);
>   
> +int kvm_s390_pci_ioat_probe(struct zpci_dev *zdev);
> +int kvm_s390_pci_ioat_enable(struct zpci_dev *zdev, u64 iota);
> +int kvm_s390_pci_ioat_disable(struct zpci_dev *zdev);
> +u8 kvm_s390_pci_get_dtsm(struct zpci_dev *zdev);
> +
>   int kvm_s390_pci_interp_probe(struct zpci_dev *zdev);
>   int kvm_s390_pci_interp_enable(struct zpci_dev *zdev);
>   int kvm_s390_pci_interp_disable(struct zpci_dev *zdev);
> diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
> index 91e63426bdc5..69e616d0712c 100644
> --- a/arch/s390/include/asm/pci_dma.h
> +++ b/arch/s390/include/asm/pci_dma.h
> @@ -50,6 +50,8 @@ enum zpci_ioat_dtype {
>   #define ZPCI_TABLE_ALIGN		ZPCI_TABLE_SIZE
>   #define ZPCI_TABLE_ENTRY_SIZE		(sizeof(unsigned long))
>   #define ZPCI_TABLE_ENTRIES		(ZPCI_TABLE_SIZE / ZPCI_TABLE_ENTRY_SIZE)
> +#define ZPCI_TABLE_PAGES		(ZPCI_TABLE_SIZE >> PAGE_SHIFT)
> +#define ZPCI_TABLE_ENTRIES_PAGES	(ZPCI_TABLE_ENTRIES * ZPCI_TABLE_PAGES)
>   
>   #define ZPCI_TABLE_BITS			11
>   #define ZPCI_PT_BITS			8
> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> index 7ed9abc476b6..39c13c25a700 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -13,12 +13,15 @@
>   #include <asm/pci.h>
>   #include <asm/pci_insn.h>
>   #include <asm/pci_io.h>
> +#include <asm/pci_dma.h>
>   #include <asm/sclp.h>
>   #include "pci.h"
>   #include "kvm-s390.h"
>   
>   struct zpci_aift *aift;
>   
> +#define shadow_ioat_init zdev->kzdev->ioat.head[0]
> +
>   static inline int __set_irq_noiib(u16 ctl, u8 isc)
>   {
>   	union zpci_sic_iib iib = {{0}};
> @@ -344,6 +347,135 @@ int kvm_s390_pci_aif_disable(struct zpci_dev *zdev)
>   }
>   EXPORT_SYMBOL_GPL(kvm_s390_pci_aif_disable);
>   
> +int kvm_s390_pci_ioat_probe(struct zpci_dev *zdev)
> +{
> +	/* Must have a KVM association registered */

may be add something like : "The ioat structure is embeded in kzdev"

> +	if (!zdev->kzdev || !zdev->kzdev->kvm)

Why do we need to check for kvm ?
Having kzdev is already tested by the unique caller.

> +		return -EINVAL;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvm_s390_pci_ioat_probe);
> +
> +int kvm_s390_pci_ioat_enable(struct zpci_dev *zdev, u64 iota)
> +{
> +	gpa_t gpa = (gpa_t)(iota & ZPCI_RTE_ADDR_MASK);
> +	struct kvm_zdev_ioat *ioat;
> +	struct page *page;
> +	struct kvm *kvm;
> +	unsigned int idx;
> +	void *iaddr;
> +	int i, rc = 0;

no need to initialize rc

> +
> +	if (shadow_ioat_init)
> +		return -EINVAL;
> +
> +	/* Ensure supported type specified */
> +	if ((iota & ZPCI_IOTA_RTTO_FLAG) != ZPCI_IOTA_RTTO_FLAG)
> +		return -EINVAL;
> +
> +	kvm = zdev->kzdev->kvm;
> +	ioat = &zdev->kzdev->ioat;
> +	mutex_lock(&ioat->lock);
> +	idx = srcu_read_lock(&kvm->srcu);
> +	for (i = 0; i < ZPCI_TABLE_PAGES; i++) {
> +		page = gfn_to_page(kvm, gpa_to_gfn(gpa));
> +		if (is_error_page(page)) {
> +			srcu_read_unlock(&kvm->srcu, idx);
> +			rc = -EIO;
> +			goto out;

			goto unpin ?

> +		}
> +		iaddr = page_to_virt(page) + (gpa & ~PAGE_MASK);
> +		ioat->head[i] = (unsigned long *)iaddr;
> +		gpa += PAGE_SIZE;
> +	}
> +	srcu_read_unlock(&kvm->srcu, idx);
> +
> +	zdev->kzdev->ioat.seg = kcalloc(ZPCI_TABLE_ENTRIES_PAGES,
> +					sizeof(unsigned long *), GFP_KERNEL);

What about:

         ioat->seg = kcalloc(ZPCI_TABLE_ENTRIES_PAGES,
                             sizeof(*ioat->seg), GFP_KERNEL);
	if (!ioat->seg)
...
	ioat->pt = ...
?

> +	if (!zdev->kzdev->ioat.seg)
> +		goto unpin;
> +	zdev->kzdev->ioat.pt = kcalloc(ZPCI_TABLE_ENTRIES,
> +				       sizeof(unsigned long **), GFP_KERNEL);
> +	if (!zdev->kzdev->ioat.pt)
> +		goto free_seg;
> +
> +out:
> +	mutex_unlock(&ioat->lock);
> +	return rc;

	return 0 ?

> +
> +free_seg:
> +	kfree(zdev->kzdev->ioat.seg);

kfree(ioat->seg) ?
rc = -ENOMEM;

> +unpin:
> +	for (i = 0; i < ZPCI_TABLE_PAGES; i++) {
> +		kvm_release_pfn_dirty((u64)ioat->head[i] >> PAGE_SHIFT);
> +		ioat->head[i] = 0;
> +	}
> +	mutex_unlock(&ioat->lock);
> +	return -ENOMEM;

	return rc;

> +}
...snip...

-- 
Pierre Morel
IBM Lab Boeblingen