On Fri, Jun 15, 2012 at 03:08:22PM -0400, Christoffer Dall wrote:
> From: Christoffer Dall <cd...@cs.columbia.edu>
>
> This commit introduces the framework for guest memory management
> through the use of 2nd stage translation. Each VM has a pointer
> to a level-1 table (the pgd field in struct kvm_arch) which is
> used for the 2nd stage translations. Entries are added when handling
> guest faults (later patch) and the table itself can be allocated and
> freed through the following functions implemented in
> arch/arm/kvm/arm_mmu.c:
> - kvm_alloc_stage2_pgd(struct kvm *kvm);
> - kvm_free_stage2_pgd(struct kvm *kvm);
>
> Further, each entry in TLBs and caches are tagged with a VMID
> identifier in addition to ASIDs. The VMIDs are assigned consecutively
> to VMs in the order that VMs are executed, and caches and tlbs are
> invalidated when the VMID space has been used to allow for more than
> 255 simultaenously running guests.
>
> The 2nd stage pgd is allocated in kvm_arch_init_vm(). The table is
> freed in kvm_arch_destroy_vm(). Both functions are called from the main
> KVM code.
>
> Signed-off-by: Christoffer Dall <c.d...@virtualopensystems.com>
> ---
> arch/arm/include/asm/kvm_arm.h | 2 -
> arch/arm/include/asm/kvm_mmu.h | 5 ++
> arch/arm/kvm/arm.c | 65 ++++++++++++++++++++++---
> arch/arm/kvm/mmu.c | 103
> ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 166 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
> index 7f30cbd..257242f 100644
> --- a/arch/arm/include/asm/kvm_arm.h
> +++ b/arch/arm/include/asm/kvm_arm.h
> @@ -62,7 +62,7 @@
> * SWIO: Turn set/way invalidates into set/way clean+invalidate
> */
> #define HCR_GUEST_MASK (HCR_TSC | HCR_TWI | HCR_VM | HCR_BSU_IS | HCR_FB | \
> - HCR_AMO | HCR_IMO | HCR_FMO | HCR_FMO | HCR_SWIO)
> + HCR_TAC | HCR_AMO | HCR_IMO | HCR_FMO | HCR_SWIO)
>
> /* Hyp System Control Register (HSCTLR) bits */
> #define HSCTLR_TE (1 << 30)
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 1aa1af4..d95662eb 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -34,4 +34,9 @@ int kvm_hyp_pgd_alloc(void);
> pgd_t *kvm_hyp_pgd_get(void);
> void kvm_hyp_pgd_free(void);
>
> +int kvm_alloc_stage2_pgd(struct kvm *kvm);
> +void kvm_free_stage2_pgd(struct kvm *kvm);
> +
> +int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
> +
> #endif /* __ARM_KVM_MMU_H__ */
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index efe130c..81babe9 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -38,6 +38,13 @@
>
> static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
>
> +/* The VMID used in the VTTBR */
> +#define VMID_BITS 8
> +#define VMID_MASK ((1 << VMID_BITS) - 1)
> +#define VMID_FIRST_GENERATION (1 << VMID_BITS)
> +static u64 next_vmid; /* The next available VMID in the
> sequence */
> +DEFINE_SPINLOCK(kvm_vmid_lock);
> +
> int kvm_arch_hardware_enable(void *garbage)
> {
> return 0;
> @@ -70,14 +77,6 @@ void kvm_arch_sync_events(struct kvm *kvm)
> {
> }
>
> -int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> -{
> - if (type)
> - return -EINVAL;
> -
> - return 0;
> -}
> -
> int kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
> {
> return VM_FAULT_SIGBUS;
> @@ -93,10 +92,46 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot,
> unsigned long npages)
> return 0;
> }
>
> +/**
> + * kvm_arch_init_vm - initializes a VM data structure
> + * @kvm: pointer to the KVM struct
> + */
> +int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> +{
> + int ret = 0;
> +
> + if (type)
> + return -EINVAL;
> +
> + ret = kvm_alloc_stage2_pgd(kvm);
> + if (ret)
> + goto out_fail_alloc;
> + mutex_init(&kvm->arch.pgd_mutex);
> +
> + ret = create_hyp_mappings(kvm, kvm + 1);
> + if (ret)
> + goto out_free_stage2_pgd;
> +
> + /* Mark the initial VMID invalid */
> + kvm->arch.vmid = 0;
> +
> + return ret;
> +out_free_stage2_pgd:
> + kvm_free_stage2_pgd(kvm);
> +out_fail_alloc:
> + return ret;
> +}
> +
> +/**
> + * kvm_arch_destroy_vm - destroy the VM data structure
> + * @kvm: pointer to the KVM struct
> + */
> void kvm_arch_destroy_vm(struct kvm *kvm)
> {
> int i;
>
> + kvm_free_stage2_pgd(kvm);
> +
> for (i = 0; i < KVM_MAX_VCPUS; ++i) {
> if (kvm->vcpus[i]) {
> kvm_arch_vcpu_free(kvm->vcpus[i]);
> @@ -172,6 +207,10 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
> unsigned int id)
> if (err)
> goto free_vcpu;
>
> + err = create_hyp_mappings(vcpu, vcpu + 1);
> + if (err)
> + goto free_vcpu;
> +
> return vcpu;
> free_vcpu:
> kmem_cache_free(kvm_vcpu_cache, vcpu);
> @@ -181,6 +220,7 @@ out:
>
> void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
> {
> + kmem_cache_free(kvm_vcpu_cache, vcpu);
> }
>
> void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> @@ -416,6 +456,15 @@ int kvm_arch_init(void *opaque)
> if (err)
> goto out_err;
>
> + /*
> + * The upper 56 bits of VMIDs are used to identify the generation
> + * counter, so VMIDs initialized to 0, having generation == 0, will
> + * never be considered valid and therefor a new VMID must always be
> + * assigned. Whent he VMID generation rolls over, we start from
> + * VMID_FIRST_GENERATION again.
> + */
> + next_vmid = VMID_FIRST_GENERATION;
> +
> return 0;
> out_err:
> return err;
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index a320b56a..b256540 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -159,6 +159,109 @@ out:
> return err;
> }
>
> +/**
> + * kvm_alloc_stage2_pgd - allocate level-1 table for stage-2 translation.
> + * @kvm: The KVM struct pointer for the VM.
> + *
> + * Allocates the 1st level table only of size defined by PGD2_ORDER (can
> + * support either full 40-bit input addresses or limited to 32-bit input
> + * addresses). Clears the allocated pages.
> + */
> +int kvm_alloc_stage2_pgd(struct kvm *kvm)
> +{
> + pgd_t *pgd;
> +
> + if (kvm->arch.pgd != NULL) {
> + kvm_err("kvm_arch already initialized?\n");
> + return -EINVAL;
> + }
> +
> + pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, PGD2_ORDER);
> + if (!pgd)
> + return -ENOMEM;
> +
> + memset(pgd, 0, PTRS_PER_PGD2 * sizeof(pgd_t));
> + kvm->arch.pgd = pgd;
> +
> + return 0;
> +}
> +
> +static void free_guest_pages(pte_t *pte, unsigned long addr)
> +{
> + unsigned int i;
> + struct page *page;
> +
> + for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
Hmm, "addr" is not used.
> + if (!pte_present(*pte))
> + goto next_page;
Why goto instead of:
if(pte_present(*pte)) {
> + page = pfn_to_page(pte_pfn(*pte));
> + put_page(page);
}
> +next_page:
> + pte++;
> + }
> +}
> +
> +static void free_stage2_ptes(pmd_t *pmd, unsigned long addr)
> +{
> + unsigned int i;
> + pte_t *pte;
> + struct page *page;
> +
> + for (i = 0; i < PTRS_PER_PMD; i++, addr += PMD_SIZE) {
> + BUG_ON(pmd_sect(*pmd));
> + if (!pmd_none(*pmd) && pmd_table(*pmd)) {
> + pte = pte_offset_kernel(pmd, addr);
> + free_guest_pages(pte, addr);
> + page = virt_to_page((void *)pte);
> + WARN_ON(atomic_read(&page->_count) != 1);
> + pte_free_kernel(NULL, pte);
> + }
> + pmd++;
> + }
> +}
> +
> +/**
> + * kvm_free_stage2_pgd - free all stage-2 tables
> + * @kvm: The KVM struct pointer for the VM.
> + *
> + * Walks the level-1 page table pointed to by kvm->arch.pgd and frees all
> + * underlying level-2 and level-3 tables before freeing the actual level-1
> table
> + * and setting the struct pointer to NULL.
> + */
> +void kvm_free_stage2_pgd(struct kvm *kvm)
> +{
> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> + unsigned long long i, addr;
> +
> + if (kvm->arch.pgd == NULL)
> + return;
> +
> + /*
> + * We do this slightly different than other places, since we need more
> + * than 32 bits and for instance pgd_addr_end converts to unsigned long.
> + */
> + addr = 0;
> + for (i = 0; i < PTRS_PER_PGD2; i++) {
> + addr = i * (unsigned long long)PGDIR_SIZE;
> + pgd = kvm->arch.pgd + i;
> + pud = pud_offset(pgd, addr);
> +
> + if (pud_none(*pud))
> + continue;
> +
> + BUG_ON(pud_bad(*pud));
> +
> + pmd = pmd_offset(pud, addr);
> + free_stage2_ptes(pmd, addr);
> + pmd_free(NULL, pmd);
> + }
> +
> + free_pages((unsigned long)kvm->arch.pgd, PGD2_ORDER);
> + kvm->arch.pgd = NULL;
> +}
> +
> int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> return -EINVAL;
>
> --
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Gleb.
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