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SubjectRe: [PATCH v9 16/21] KVM: s390: pci: add routines to start/stop interpretive execution
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On 6/6/22 22:33, Matthew Rosato wrote:
> These routines will be invoked at the time an s390x vfio-pci device is
> associated with a KVM (or when the association is removed), allowing
> the zPCI device to enable or disable load/store intepretation mode;
> this requires the host zPCI device to inform firmware of the unique
> token (GISA designation) that is associated with the owning KVM.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 18 ++++
> arch/s390/include/asm/pci.h | 1 +
> arch/s390/kvm/kvm-s390.c | 15 +++
> arch/s390/kvm/pci.c | 162 +++++++++++++++++++++++++++++++
> arch/s390/kvm/pci.h | 5 +
> arch/s390/pci/pci.c | 4 +
> 6 files changed, 205 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 8e381603b6a7..6e83d746bae2 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -19,6 +19,7 @@
> #include <linux/kvm.h>
> #include <linux/seqlock.h>
> #include <linux/module.h>
> +#include <linux/pci.h>
> #include <asm/debug.h>
> #include <asm/cpu.h>
> #include <asm/fpu/api.h>
> @@ -967,6 +968,8 @@ struct kvm_arch{
> DECLARE_BITMAP(idle_mask, KVM_MAX_VCPUS);
> struct kvm_s390_gisa_interrupt gisa_int;
> struct kvm_s390_pv pv;
> + struct list_head kzdev_list;
> + spinlock_t kzdev_list_lock;
> };
>
> #define KVM_HVA_ERR_BAD (-1UL)
> @@ -1017,4 +1020,19 @@ static inline void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
> static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
>
> +#define __KVM_HAVE_ARCH_VM_FREE
> +void kvm_arch_free_vm(struct kvm *kvm);
> +
> +#ifdef CONFIG_VFIO_PCI_ZDEV_KVM
> +int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm);
> +void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev);
> +#else
> +static inline int kvm_s390_pci_register_kvm(struct zpci_dev *dev,
> + struct kvm *kvm)
> +{
> + return -EPERM;
> +}
> +static inline void kvm_s390_pci_unregister_kvm(struct zpci_dev *dev) {}
> +#endif
> +
> #endif
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 322060a75d9f..85eb0ef9d4c3 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -194,6 +194,7 @@ struct zpci_dev {
> /* IOMMU and passthrough */
> struct s390_domain *s390_domain; /* s390 IOMMU domain data */
> struct kvm_zdev *kzdev;
> + struct mutex kzdev_lock;

I guess that since it did not exist before the lock is not there to
protect the zpci_dev struct.
May be add a comment to say what it is protecting.


> };
>
> static inline bool zdev_enabled(struct zpci_dev *zdev)
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index a66da3f66114..4758bb731199 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2790,6 +2790,14 @@ static void sca_dispose(struct kvm *kvm)
> kvm->arch.sca = NULL;
> }
>
> +void kvm_arch_free_vm(struct kvm *kvm)
> +{
> + if (IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM))
> + kvm_s390_pci_clear_list(kvm);
> +
> + __kvm_arch_free_vm(kvm);
> +}
> +
> int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> {
> gfp_t alloc_flags = GFP_KERNEL_ACCOUNT;
> @@ -2872,6 +2880,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>
> kvm_s390_crypto_init(kvm);
>
> + if (IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)) {
> + mutex_lock(&kvm->lock);
> + kvm_s390_pci_init_list(kvm);
> + kvm_s390_vcpu_pci_enable_interp(kvm);
> + mutex_unlock(&kvm->lock);
> + }
> +
> mutex_init(&kvm->arch.float_int.ais_lock);
> spin_lock_init(&kvm->arch.float_int.lock);
> for (i = 0; i < FIRQ_LIST_COUNT; i++)
> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> index b232c8cbaa81..24211741deb0 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -12,7 +12,9 @@
> #include <asm/pci.h>
> #include <asm/pci_insn.h>
> #include <asm/pci_io.h>
> +#include <asm/sclp.h>
> #include "pci.h"
> +#include "kvm-s390.h"
>
> struct zpci_aift *aift;
>
> @@ -423,6 +425,166 @@ static void kvm_s390_pci_dev_release(struct zpci_dev *zdev)
> kfree(kzdev);
> }
>
> +
> +/*
> + * Register device with the specified KVM. If interpetation facilities are
> + * available, enable them and let userspace indicate whether or not they will
> + * be used (specify SHM bit to disable).
> + */
> +int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm)
> +{
> + int rc;
> +
> + if (!zdev)
> + return -EINVAL;
> +
> + mutex_lock(&zdev->kzdev_lock);
> +
> + if (zdev->kzdev || zdev->gisa != 0 || !kvm) {
> + mutex_unlock(&zdev->kzdev_lock);
> + return -EINVAL;
> + }
> +
> + kvm_get_kvm(kvm);
> +
> + mutex_lock(&kvm->lock);

Why do we need to lock KVM here?

just a question, I do not think it is a big problem.

> +
> + rc = kvm_s390_pci_dev_open(zdev);
> + if (rc)
> + goto err;
> +
> + /*
> + * If interpretation facilities aren't available, add the device to
> + * the kzdev list but don't enable for interpretation.
> + */
> + if (!kvm_s390_pci_interp_allowed())
> + goto out;
> +
> + /*
> + * If this is the first request to use an interpreted device, make the
> + * necessary vcpu changes
> + */
> + if (!kvm->arch.use_zpci_interp)
> + kvm_s390_vcpu_pci_enable_interp(kvm);
> +
> + if (zdev_enabled(zdev)) {
> + rc = zpci_disable_device(zdev);
> + if (rc)
> + goto err;
> + }
> +
> + /*
> + * Store information about the identity of the kvm guest allowed to
> + * access this device via interpretation to be used by host CLP
> + */
> + zdev->gisa = (u32)virt_to_phys(&kvm->arch.sie_page2->gisa);
> +
> + rc = zpci_enable_device(zdev);
> + if (rc)
> + goto clear_gisa;
> +
> + /* Re-register the IOMMU that was already created */
> + rc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
> + virt_to_phys(zdev->dma_table));
> + if (rc)
> + goto clear_gisa;
> +
> +out:
> + zdev->kzdev->kvm = kvm;
> +
> + spin_lock(&kvm->arch.kzdev_list_lock);
> + list_add_tail(&zdev->kzdev->entry, &kvm->arch.kzdev_list);
> + spin_unlock(&kvm->arch.kzdev_list_lock);
> +
> + mutex_unlock(&kvm->lock);
> + mutex_unlock(&zdev->kzdev_lock);
> + return 0;
> +
> +clear_gisa:
> + zdev->gisa = 0;
> +err:
> + if (zdev->kzdev)
> + kvm_s390_pci_dev_release(zdev);
> + mutex_unlock(&kvm->lock);
> + mutex_unlock(&zdev->kzdev_lock);
> + kvm_put_kvm(kvm);
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(kvm_s390_pci_register_kvm);
> +
> +void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev)
> +{
> + struct kvm *kvm;
> +
> + if (!zdev)
> + return;
> +
> + mutex_lock(&zdev->kzdev_lock);
> +
> + if (WARN_ON(!zdev->kzdev)) {

When can this happen ?

> + mutex_unlock(&zdev->kzdev_lock);
> + return;
> + }
> +
> + kvm = zdev->kzdev->kvm;
> + mutex_lock(&kvm->lock);
> +
> + /*
> + * A 0 gisa means interpretation was never enabled, just remove the
> + * device from the list.
> + */
> + if (zdev->gisa == 0)
> + goto out;
> +
> + /* Forwarding must be turned off before interpretation */
> + if (zdev->kzdev->fib.fmt0.aibv != 0)
> + kvm_s390_pci_aif_disable(zdev, true);
> +
> + /* Remove the host CLP guest designation */
> + zdev->gisa = 0;
> +
> + if (zdev_enabled(zdev)) {
> + if (zpci_disable_device(zdev))
> + goto out;

NIT debug trace ?

> + }
> +
> + if (zpci_enable_device(zdev))
> + goto out;

NIT debug trace?

Only some questions, otherwise, LGTM

Acked-by: Pierre Morel <pmorel@linux.ibm.com>

--
Pierre Morel
IBM Lab Boeblingen

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