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Message-ID: <6fe34d89-5e38-86ef-ded1-cc1463c95294@linux.ibm.com>
Date: Wed, 26 Jan 2022 09:30:56 +0100
From: Pierre Morel <pmorel@...ux.ibm.com>
To: Matthew Rosato <mjrosato@...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 15:47, Matthew Rosato wrote:
> 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)
I thought the check could be done even if the userspace is not
associated with KVM. But of course OK if Alex asked I would have missed
some point.
--
Pierre Morel
IBM Lab Boeblingen
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