Re: [PATCH 22/32] KVM: s390: pci: provide routines for enabling/disabling IOAT assist

Pierre Morel
2021-12-14T17:45:55Z

On 12/7/21 21:57, 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 | 133 ++++++++++++++++++++++++++++++++
> arch/s390/kvm/pci.h | 2 +
> 4 files changed, 152 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index 54a0afdbe7d0..254275399f21 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;
> +};
>
> struct kvm_zdev {
> struct zpci_dev *zdev;
> struct kvm *kvm;
> + struct kvm_zdev_ioat ioat;
> struct zpci_fib fib;
> };
>
> @@ -33,6 +43,11 @@ extern int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
> bool assist);
> extern int kvm_s390_pci_aif_disable(struct zpci_dev *zdev);
>
> +extern int kvm_s390_pci_ioat_probe(struct zpci_dev *zdev);
> +extern int kvm_s390_pci_ioat_enable(struct zpci_dev *zdev, u64 iota);
> +extern int kvm_s390_pci_ioat_disable(struct zpci_dev *zdev);
> +extern u8 kvm_s390_pci_get_dtsm(struct zpci_dev *zdev);
> +
> extern int kvm_s390_pci_interp_probe(struct zpci_dev *zdev);
> extern int kvm_s390_pci_interp_enable(struct zpci_dev *zdev);
> extern 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 3b8e89d4578a..e1d3c1d3fc8a 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 3a29398dd53b..a1c0c0881332 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -12,6 +12,7 @@
> #include <asm/kvm_pci.h>
> #include <asm/pci.h>
> #include <asm/pci_insn.h>
> +#include <asm/pci_dma.h>
> #include <asm/sclp.h>
> #include "pci.h"
> #include "kvm-s390.h"
> @@ -315,6 +316,131 @@ 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)
> +{
> + 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;
> +
> + if (!zdev->kzdev || !zdev->kzdev->kvm || zdev->kzdev->ioat.head[0])
> + return -EINVAL;

The only caller already checked zdev->kzdev.
Could we use a macro to replace zdev->kzdev->ioat.head[0] ?
like
#define shadow_pgtbl_initialized zdev->kzdev->ioat.head[0]

Would be clearer for me.

> +
> + /* 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;
> + }
> + 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);
> + 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;
> +
> +free_seg:
> + kfree(zdev->kzdev->ioat.seg);
> +unpin:
> + for (i = 0; i < ZPCI_TABLE_PAGES; i++) {
> + kvm_release_pfn_dirty((u64)ioat->head[i] >> PAGE_SHIFT);

I did not find when the pages are pinned.

> + ioat->head[i] = 0;
> + }
> + mutex_unlock(&ioat->lock);
> + return -ENOMEM;
> +}
> +EXPORT_SYMBOL_GPL(kvm_s390_pci_ioat_enable);
> +

...snip...
>

--
Pierre Morel
IBM Lab Boeblingen