linux-kernel - Re: [PATCH 23/32] KVM: s390: pci: handle refresh of PCI translations

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Date:   Tue, 14 Dec 2021 17:59:31 +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 23/32] KVM: s390: pci: handle refresh of PCI translations



On 12/7/21 21:57, Matthew Rosato wrote:
> Add a routine that will perform a shadow operation between a guest
> and host IOAT.  A subsequent patch will invoke this in response to
> an 04 RPCIT instruction intercept.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>   arch/s390/include/asm/kvm_pci.h |   1 +
>   arch/s390/include/asm/pci_dma.h |   1 +
>   arch/s390/kvm/pci.c             | 191 ++++++++++++++++++++++++++++++++
>   arch/s390/kvm/pci.h             |   4 +-
>   4 files changed, 196 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index 254275399f21..97e3a369135d 100644
> --- a/arch/s390/include/asm/kvm_pci.h
> +++ b/arch/s390/include/asm/kvm_pci.h
> @@ -30,6 +30,7 @@ struct kvm_zdev_ioat {
>   struct kvm_zdev {
>   	struct zpci_dev *zdev;
>   	struct kvm *kvm;
> +	u64 rpcit_count;
>   	struct kvm_zdev_ioat ioat;
>   	struct zpci_fib fib;
>   };
> diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
> index e1d3c1d3fc8a..0ca15e5db3d9 100644
> --- a/arch/s390/include/asm/pci_dma.h
> +++ b/arch/s390/include/asm/pci_dma.h
> @@ -52,6 +52,7 @@ enum zpci_ioat_dtype {
>   #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_ENTRIES_PER_PAGE	(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 a1c0c0881332..858c5ecdc8b9 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -123,6 +123,195 @@ int kvm_s390_pci_aen_init(u8 nisc)
>   	return rc;
>   }

...snip...

> +
> +int kvm_s390_pci_refresh_trans(struct kvm_vcpu *vcpu, unsigned long req,
> +			       unsigned long start, unsigned long size)
> +{
> +	struct zpci_dev *zdev;
> +	u32 fh;
> +	int rc;
> +
> +	/* If the device has a SHM bit on, let userspace take care of this */
> +	fh = req >> 32;
> +	if ((fh & aift.mdd) != 0)
> +		return -EOPNOTSUPP;

I think you should make this check in the caller.

> +
> +	/* Make sure this is a valid device associated with this guest */
> +	zdev = get_zdev_by_fh(fh);
> +	if (!zdev || !zdev->kzdev || zdev->kzdev->kvm != vcpu->kvm)
> +		return -EINVAL;
> +
> +	/* Only proceed if the device is using the assist */
> +	if (zdev->kzdev->ioat.head[0] == 0)
> +		return -EOPNOTSUPP;

Using the assist means using interpretation over using interception and 
legacy vfio-pci. right?

> +
> +	rc = dma_table_shadow(vcpu, zdev, start, size);
> +	if (rc > 0)
> +		rc = zpci_refresh_trans((u64) zdev->fh << 32, start, size);

Here you lose the status reported by the hardware.
You should directly use __rpcit(fn, addr, range, &status);


> +	zdev->kzdev->rpcit_count++;
> +
> +	return rc;
> +}
> +
>   /* Modify PCI: Register floating adapter interruption forwarding */
>   static int kvm_zpci_set_airq(struct zpci_dev *zdev)
>   {
> @@ -590,4 +779,6 @@ void kvm_s390_pci_init(void)
>   {
>   	spin_lock_init(&aift.gait_lock);
>   	mutex_init(&aift.lock);
> +
> +	WARN_ON(zpci_get_mdd(&aift.mdd));
>   }
> diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
> index 3c86888fe1b3..d252a631b693 100644
> --- a/arch/s390/kvm/pci.h
> +++ b/arch/s390/kvm/pci.h
> @@ -33,6 +33,7 @@ struct zpci_aift {
>   	struct kvm_zdev **kzdev;
>   	spinlock_t gait_lock; /* Protects the gait, used during AEN forward */
>   	struct mutex lock; /* Protects the other structures in aift */
> +	u32 mdd;
>   };
>   
>   static inline struct kvm *kvm_s390_pci_si_to_kvm(struct zpci_aift *aift,
> @@ -47,7 +48,8 @@ struct zpci_aift *kvm_s390_pci_get_aift(void);
>   
>   int kvm_s390_pci_aen_init(u8 nisc);
>   void kvm_s390_pci_aen_exit(void);
> -
> +int kvm_s390_pci_refresh_trans(struct kvm_vcpu *vcpu, unsigned long req,
> +			       unsigned long start, unsigned long end);
>   void kvm_s390_pci_init(void);
>   
>   #endif /* __KVM_S390_PCI_H */
> 

-- 
Pierre Morel
IBM Lab Boeblingen