On 15.02.2018 16:43, Janosch Frank wrote:
> Now that we have everything in place, let's allow huge (1m) pmds for
> gmap linking, effectively allowing hugetlbfs backed guests. Transparent
> huge pages and 2g huge pages are *not* supported through this change.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/virtual/kvm/api.txt | 12 ++++++++++++
> arch/s390/include/asm/mmu.h | 2 ++
> arch/s390/include/asm/mmu_context.h | 1 +
> arch/s390/kvm/kvm-s390.c | 17 ++++++++++++++++-
> arch/s390/mm/gmap.c | 8 +++++---
> include/uapi/linux/kvm.h | 1 +
> 6 files changed, 37 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 792fa87..edf248a 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -4270,6 +4270,18 @@ enables QEMU to build error log and branch to guest kernel registered
> machine check handling routine. Without this capability KVM will
> branch to guests' 0x200 interrupt vector.
>
> +7.13 KVM_CAP_S390_HPAGE
> +
> +Architectures: s390
> +Parameters: none
> +
> +With this capability the KVM support for memory backing with 1m pages
> +through hugetlbfs can be enabled. This will disable cmm, cmma, pfmfi
> +and the storage key interpretation.
> +
> +While it is generally possible to create and start a huge page backed
> +VM without this capability, the VM will not be functional.
> +
> 8. Other capabilities.
> ----------------------
>
> diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
> index db35c41a..5ab9452 100644
> --- a/arch/s390/include/asm/mmu.h
> +++ b/arch/s390/include/asm/mmu.h
> @@ -24,6 +24,8 @@ typedef struct {
> unsigned int use_skey:1;
> /* The mmu context uses CMMA. */
> unsigned int use_cmma:1;
> + /* The gmap associated with this context uses huge pages. */
> + unsigned int use_gmap_hpage:1;
> } mm_context_t;
>
> #define INIT_MM_CONTEXT(name) \
> diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
> index 65154ea..79f2159 100644
> --- a/arch/s390/include/asm/mmu_context.h
> +++ b/arch/s390/include/asm/mmu_context.h
> @@ -32,6 +32,7 @@ static inline int init_new_context(struct task_struct *tsk,
> mm->context.has_pgste = 0;
> mm->context.use_skey = 0;
> mm->context.use_cmma = 0;
> + mm->context.use_gmap_hpage = 0;
> #endif
> switch (mm->context.asce_limit) {
> case _REGION2_SIZE:
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index ddf3599..8ea7025 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -406,6 +406,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_S390_CMMA_MIGRATION:
> case KVM_CAP_S390_AIS:
> case KVM_CAP_S390_AIS_MIGRATION:
> + case KVM_CAP_S390_HPAGE:
> r = 1;
> break;
> case KVM_CAP_S390_MEM_OP:
> @@ -604,6 +605,19 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
> VM_EVENT(kvm, 3, "ENABLE: CAP_S390_GS %s",
> r ? "(not available)" : "(success)");
> break;
> + case KVM_CAP_S390_HPAGE:
> + mutex_lock(&kvm->lock);
> + if (kvm->created_vcpus) {
> + r = -EBUSY;
> + }
> + kvm->mm->context.use_gmap_hpage = 1;
> + /* They would complicate matters too much. */
> + kvm->arch.has_skf = 0;
> + kvm->arch.has_cmma = 0;
> + kvm->arch.has_pfmfi = 0;
> + mutex_unlock(&kvm->lock);
> + VM_EVENT(kvm, 3, "%s", "ENABLE: KVM_CAP_S390_HPAGE");
> + break;
> case KVM_CAP_S390_USER_STSI:
> VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_STSI");
> kvm->arch.user_stsi = 1;
> @@ -655,7 +669,8 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
> VM_EVENT(kvm, 3, "%s", "ENABLE: CMMA support");
> mutex_lock(&kvm->lock);
> if (!kvm->created_vcpus) {
> - kvm->arch.has_cmma = 1;
> + if (!kvm->mm->context.use_gmap_hpage)
> + kvm->arch.has_cmma = 1;
> /* Not compatible with cmma. */
> kvm->arch.has_pfmfi = 0;
As Christian said, this should be an XOR.
Either KVM_CAP_S390_HPAGE or CMMA can be enabled, not both (-EINVAL).
> ret = 0;
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 2cafcba..6937853 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2,8 +2,10 @@
> /*
> * KVM guest address space mapping code
> *
> - * Copyright IBM Corp. 2007, 2016
> + * Copyright IBM Corp. 2007, 2016, 2017
> * Author(s): Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> + * David Hildenbrand <david@xxxxxxxxxx>
> + * Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> */
>
> #include <linux/kernel.h>
> @@ -595,8 +597,8 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
> return -EFAULT;
> pmd = pmd_offset(pud, vmaddr);
> VM_BUG_ON(pmd_none(*pmd));
> - /* large pmds cannot yet be handled */
> - if (pmd_large(*pmd))
> + /* Are we allowed to use huge pages? */
> + if (pmd_large(*pmd) && !gmap->mm->context.use_gmap_hpage)
> return -EFAULT;
> /* Link gmap segment table entry location to page table. */
> rc = radix_tree_preload(GFP_KERNEL);
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 0fb5ef9..4e397d7 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -934,6 +934,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_S390_AIS_MIGRATION 150
> #define KVM_CAP_PPC_GET_CPU_CHAR 151
> #define KVM_CAP_S390_BPB 152
> +#define KVM_CAP_S390_HPAGE 153
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
>
--
Thanks,
David / dhildenb
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