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Message-ID: <5de7c3ef-9c25-56d3-cc46-e002f8742dbe@linux.ibm.com>
Date: Tue, 25 Jan 2022 09:47:55 -0500
From: Matthew Rosato <mjrosato@...ux.ibm.com>
To: Pierre Morel <pmorel@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc: alex.williamson@...hat.com, cohuck@...hat.com,
schnelle@...ux.ibm.com, farman@...ux.ibm.com,
borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 20/30] KVM: s390: pci: provide routines for
enabling/disabling IOAT assist
On 1/25/22 8:29 AM, Pierre Morel wrote:
>
>
> 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@...ux.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?
>
OK. The lock is meant to protect the contents of kvm_zdev_ioat -- I'll
think of something to describe it.
>> +};
>> 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.
>
We probably don't need to check for the kzdev because the caller already
did this, agreed there.
But as for checking the kvm association, Alex asked for this in a
comment to v1 (comment was against one of the vfio patches that call
these routines) -- The reason being the probe comes from a userspace
request and can be against any vfio-pci(-zdev) device at any time, and
there's no point in proceeding if this device is not associated with a
KVM guest -- It's possible for the KVM notifier to also pass a null KVM
address -- so I think it's better to just be sure here. In a
well-behaved environment we would never see this (so, another case for
an s390dbf entry)
>> + 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
Agree based on the changes below
>
>> +
>> + 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 ?
Ah, right, in case we hit this error somewhere in the middle of the loop.
>
>> + }
>> + 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 = ...
> ?
Yep, would be fine (seems I forgot about the local *ioat here)
>
>> + 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 ?
Yes, we can do that now that we don't goto out: after is_error_page
>
>> +
>> +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;
And yes, agreed, now that we come here for other reasons (-EIO) we must
return rc here and also set rc=-ENOMEM as you say for the kfree case above.
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