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    Subject[PATCH 33/40] KVM: x86: switch kvm_set_memory_alias to SRCU update
    Date
    From: Marcelo Tosatti <mtosatti@redhat.com>

    Using a similar two-step procedure as for memslots.

    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    ---
    arch/x86/include/asm/kvm_host.h | 4 ++
    arch/x86/kvm/x86.c | 60 +++++++++++++++++++++++++++++++++------
    include/linux/kvm_host.h | 6 ++++
    virt/kvm/kvm_main.c | 4 +-
    4 files changed, 63 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index 7cdcb3d..6c8c7c5 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -368,8 +368,12 @@ struct kvm_mem_alias {
    gfn_t base_gfn;
    unsigned long npages;
    gfn_t target_gfn;
    +#define KVM_ALIAS_INVALID 1UL
    + unsigned long flags;
    };

    +#define KVM_ARCH_HAS_UNALIAS_INSTANTIATION
    +
    struct kvm_mem_aliases {
    struct kvm_mem_alias aliases[KVM_ALIAS_SLOTS];
    int naliases;
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 2d7c040..59f4da4 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -38,6 +38,7 @@
    #include <linux/intel-iommu.h>
    #include <linux/cpufreq.h>
    #include <linux/user-return-notifier.h>
    +#include <linux/srcu.h>
    #include <trace/events/kvm.h>
    #undef TRACE_INCLUDE_FILE
    #define CREATE_TRACE_POINTS
    @@ -2224,11 +2225,32 @@ static int kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
    return kvm->arch.n_alloc_mmu_pages;
    }

    +gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn)
    +{
    + int i;
    + struct kvm_mem_alias *alias;
    + struct kvm_mem_aliases *aliases;
    +
    + aliases = rcu_dereference(kvm->arch.aliases);
    +
    + for (i = 0; i < aliases->naliases; ++i) {
    + alias = &aliases->aliases[i];
    + if (alias->flags & KVM_ALIAS_INVALID)
    + continue;
    + if (gfn >= alias->base_gfn
    + && gfn < alias->base_gfn + alias->npages)
    + return alias->target_gfn + gfn - alias->base_gfn;
    + }
    + return gfn;
    +}
    +
    gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
    {
    int i;
    struct kvm_mem_alias *alias;
    - struct kvm_mem_aliases *aliases = kvm->arch.aliases;
    + struct kvm_mem_aliases *aliases;
    +
    + aliases = rcu_dereference(kvm->arch.aliases);

    for (i = 0; i < aliases->naliases; ++i) {
    alias = &aliases->aliases[i];
    @@ -2249,7 +2271,7 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm,
    {
    int r, n;
    struct kvm_mem_alias *p;
    - struct kvm_mem_aliases *aliases;
    + struct kvm_mem_aliases *aliases, *old_aliases;

    r = -EINVAL;
    /* General sanity checks */
    @@ -2266,28 +2288,48 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm,
    < alias->target_phys_addr)
    goto out;

    + r = -ENOMEM;
    + aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
    + if (!aliases)
    + goto out;
    +
    down_write(&kvm->slots_lock);
    - spin_lock(&kvm->mmu_lock);

    - aliases = kvm->arch.aliases;
    + /* invalidate any gfn reference in case of deletion/shrinking */
    + memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));
    + aliases->aliases[alias->slot].flags |= KVM_ALIAS_INVALID;
    + old_aliases = kvm->arch.aliases;
    + rcu_assign_pointer(kvm->arch.aliases, aliases);
    + synchronize_srcu_expedited(&kvm->srcu);
    + kvm_mmu_zap_all(kvm);
    + kfree(old_aliases);
    +
    + r = -ENOMEM;
    + aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
    + if (!aliases)
    + goto out_unlock;
    +
    + memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));

    p = &aliases->aliases[alias->slot];
    p->base_gfn = alias->guest_phys_addr >> PAGE_SHIFT;
    p->npages = alias->memory_size >> PAGE_SHIFT;
    p->target_gfn = alias->target_phys_addr >> PAGE_SHIFT;
    + p->flags &= ~(KVM_ALIAS_INVALID);

    for (n = KVM_ALIAS_SLOTS; n > 0; --n)
    if (aliases->aliases[n - 1].npages)
    break;
    aliases->naliases = n;

    - spin_unlock(&kvm->mmu_lock);
    - kvm_mmu_zap_all(kvm);
    + old_aliases = kvm->arch.aliases;
    + rcu_assign_pointer(kvm->arch.aliases, aliases);
    + synchronize_srcu_expedited(&kvm->srcu);
    + kfree(old_aliases);
    + r = 0;

    +out_unlock:
    up_write(&kvm->slots_lock);
    -
    - return 0;
    -
    out:
    return r;
    }
    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index 93bd307..20941c0 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -266,6 +266,8 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
    void kvm_disable_largepages(void);
    void kvm_arch_flush_shadow(struct kvm *kvm);
    gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn);
    +gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn);
    +
    struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
    unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
    void kvm_release_page_clean(struct page *page);
    @@ -539,6 +541,10 @@ static inline int mmu_notifier_retry(struct kvm_vcpu *vcpu, unsigned long mmu_se
    }
    #endif

    +#ifndef KVM_ARCH_HAS_UNALIAS_INSTANTIATION
    +#define unalias_gfn_instantiation unalias_gfn
    +#endif
    +
    #ifdef CONFIG_HAVE_KVM_IRQCHIP

    #define KVM_MAX_IRQ_ROUTES 1024
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 2bb24a8..c680f7b 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -859,7 +859,7 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
    int i;
    struct kvm_memslots *slots = rcu_dereference(kvm->memslots);

    - gfn = unalias_gfn(kvm, gfn);
    + gfn = unalias_gfn_instantiation(kvm, gfn);
    for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
    struct kvm_memory_slot *memslot = &slots->memslots[i];

    @@ -896,7 +896,7 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
    {
    struct kvm_memory_slot *slot;

    - gfn = unalias_gfn(kvm, gfn);
    + gfn = unalias_gfn_instantiation(kvm, gfn);
    slot = gfn_to_memslot_unaliased(kvm, gfn);
    if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
    return bad_hva();
    --
    1.6.5.3


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