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    Subject[PATCH 19/36] KVM: ppc: support large host pages
    Date
    From: Hollis Blanchard <hollisb@us.ibm.com>

    KVM on 440 has always been able to handle large guest mappings with 4K host
    pages -- we must, since the guest kernel uses 256MB mappings.

    This patch makes KVM work when the host has large pages too (tested with 64K).

    Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
    Signed-off-by: Avi Kivity <avi@redhat.com>
    ---
    arch/powerpc/include/asm/kvm_ppc.h | 4 +-
    arch/powerpc/kvm/44x_tlb.c | 71 ++++++++++++++++++++++++++++--------
    arch/powerpc/kvm/booke.c | 12 ++++---
    3 files changed, 64 insertions(+), 23 deletions(-)

    diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
    index 844f683..5bb2926 100644
    --- a/arch/powerpc/include/asm/kvm_ppc.h
    +++ b/arch/powerpc/include/asm/kvm_ppc.h
    @@ -52,8 +52,8 @@ extern int kvmppc_emulate_instruction(struct kvm_run *run,
    extern int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu);
    extern void kvmppc_emulate_dec(struct kvm_vcpu *vcpu);

    -extern void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn,
    - u64 asid, u32 flags);
    +extern void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gpa_t gpaddr,
    + u64 asid, u32 flags, u32 max_bytes);
    extern void kvmppc_mmu_priv_switch(struct kvm_vcpu *vcpu, int usermode);
    extern void kvmppc_mmu_switch_pid(struct kvm_vcpu *vcpu, u32 pid);

    diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
    index ee24618..d49dc66 100644
    --- a/arch/powerpc/kvm/44x_tlb.c
    +++ b/arch/powerpc/kvm/44x_tlb.c
    @@ -28,6 +28,13 @@

    #include "44x_tlb.h"

    +#ifndef PPC44x_TLBE_SIZE
    +#define PPC44x_TLBE_SIZE PPC44x_TLB_4K
    +#endif
    +
    +#define PAGE_SIZE_4K (1<<12)
    +#define PAGE_MASK_4K (~(PAGE_SIZE_4K - 1))
    +
    #define PPC44x_TLB_UATTR_MASK \
    (PPC44x_TLB_U0|PPC44x_TLB_U1|PPC44x_TLB_U2|PPC44x_TLB_U3)
    #define PPC44x_TLB_USER_PERM_MASK (PPC44x_TLB_UX|PPC44x_TLB_UR|PPC44x_TLB_UW)
    @@ -179,15 +186,26 @@ void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
    vcpu_44x->shadow_tlb_mod[i] = 1;
    }

    -/* Caller must ensure that the specified guest TLB entry is safe to insert into
    - * the shadow TLB. */
    -void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
    - u32 flags)
    +/**
    + * kvmppc_mmu_map -- create a host mapping for guest memory
    + *
    + * If the guest wanted a larger page than the host supports, only the first
    + * host page is mapped here and the rest are demand faulted.
    + *
    + * If the guest wanted a smaller page than the host page size, we map only the
    + * guest-size page (i.e. not a full host page mapping).
    + *
    + * Caller must ensure that the specified guest TLB entry is safe to insert into
    + * the shadow TLB.
    + */
    +void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gpa_t gpaddr, u64 asid,
    + u32 flags, u32 max_bytes)
    {
    struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
    struct page *new_page;
    struct kvmppc_44x_tlbe *stlbe;
    hpa_t hpaddr;
    + gfn_t gfn;
    unsigned int victim;

    /* Future optimization: don't overwrite the TLB entry containing the
    @@ -198,6 +216,7 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
    stlbe = &vcpu_44x->shadow_tlb[victim];

    /* Get reference to new page. */
    + gfn = gpaddr >> PAGE_SHIFT;
    new_page = gfn_to_page(vcpu->kvm, gfn);
    if (is_error_page(new_page)) {
    printk(KERN_ERR "Couldn't get guest page for gfn %lx!\n", gfn);
    @@ -220,10 +239,25 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
    stlbe->tid = !(asid & 0xff);

    /* Force TS=1 for all guest mappings. */
    - /* For now we hardcode 4KB mappings, but it will be important to
    - * use host large pages in the future. */
    - stlbe->word0 = (gvaddr & PAGE_MASK) | PPC44x_TLB_VALID | PPC44x_TLB_TS
    - | PPC44x_TLB_4K;
    + stlbe->word0 = PPC44x_TLB_VALID | PPC44x_TLB_TS;
    +
    + if (max_bytes >= PAGE_SIZE) {
    + /* Guest mapping is larger than or equal to host page size. We can use
    + * a "native" host mapping. */
    + stlbe->word0 |= (gvaddr & PAGE_MASK) | PPC44x_TLBE_SIZE;
    + } else {
    + /* Guest mapping is smaller than host page size. We must restrict the
    + * size of the mapping to be at most the smaller of the two, but for
    + * simplicity we fall back to a 4K mapping (this is probably what the
    + * guest is using anyways). */
    + stlbe->word0 |= (gvaddr & PAGE_MASK_4K) | PPC44x_TLB_4K;
    +
    + /* 'hpaddr' is a host page, which is larger than the mapping we're
    + * inserting here. To compensate, we must add the in-page offset to the
    + * sub-page. */
    + hpaddr |= gpaddr & (PAGE_MASK ^ PAGE_MASK_4K);
    + }
    +
    stlbe->word1 = (hpaddr & 0xfffffc00) | ((hpaddr >> 32) & 0xf);
    stlbe->word2 = kvmppc_44x_tlb_shadow_attrib(flags,
    vcpu->arch.msr & MSR_PR);
    @@ -322,10 +356,8 @@ static int tlbe_is_host_safe(const struct kvm_vcpu *vcpu,
    int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
    {
    struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
    - u64 eaddr;
    - u64 raddr;
    + gva_t eaddr;
    u64 asid;
    - u32 flags;
    struct kvmppc_44x_tlbe *tlbe;
    unsigned int index;

    @@ -364,15 +396,22 @@ int kvmppc_44x_emul_tlbwe(struct kvm_vcpu *vcpu, u8 ra, u8 rs, u8 ws)
    }

    if (tlbe_is_host_safe(vcpu, tlbe)) {
    + gpa_t gpaddr;
    + u32 flags;
    + u32 bytes;
    +
    eaddr = get_tlb_eaddr(tlbe);
    - raddr = get_tlb_raddr(tlbe);
    + gpaddr = get_tlb_raddr(tlbe);
    +
    + /* Use the advertised page size to mask effective and real addrs. */
    + bytes = get_tlb_bytes(tlbe);
    + eaddr &= ~(bytes - 1);
    + gpaddr &= ~(bytes - 1);
    +
    asid = (tlbe->word0 & PPC44x_TLB_TS) | tlbe->tid;
    flags = tlbe->word2 & 0xffff;

    - /* Create a 4KB mapping on the host. If the guest wanted a
    - * large page, only the first 4KB is mapped here and the rest
    - * are mapped on the fly. */
    - kvmppc_mmu_map(vcpu, eaddr, raddr >> PAGE_SHIFT, asid, flags);
    + kvmppc_mmu_map(vcpu, eaddr, gpaddr, asid, flags, bytes);
    }

    KVMTRACE_5D(GTLB_WRITE, vcpu, index,
    diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
    index ec59a67..924c7b4 100644
    --- a/arch/powerpc/kvm/booke.c
    +++ b/arch/powerpc/kvm/booke.c
    @@ -308,8 +308,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
    * b) the guest used a large mapping which we're faking
    * Either way, we need to satisfy the fault without
    * invoking the guest. */
    - kvmppc_mmu_map(vcpu, eaddr, gfn, gtlbe->tid,
    - gtlbe->word2);
    + kvmppc_mmu_map(vcpu, eaddr, vcpu->arch.paddr_accessed, gtlbe->tid,
    + gtlbe->word2, get_tlb_bytes(gtlbe));
    vcpu->stat.dtlb_virt_miss_exits++;
    r = RESUME_GUEST;
    } else {
    @@ -325,6 +325,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
    case BOOKE_INTERRUPT_ITLB_MISS: {
    struct kvmppc_44x_tlbe *gtlbe;
    unsigned long eaddr = vcpu->arch.pc;
    + gpa_t gpaddr;
    gfn_t gfn;

    r = RESUME_GUEST;
    @@ -340,7 +341,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,

    vcpu->stat.itlb_virt_miss_exits++;

    - gfn = tlb_xlate(gtlbe, eaddr) >> PAGE_SHIFT;
    + gpaddr = tlb_xlate(gtlbe, eaddr);
    + gfn = gpaddr >> PAGE_SHIFT;

    if (kvm_is_visible_gfn(vcpu->kvm, gfn)) {
    /* The guest TLB had a mapping, but the shadow TLB
    @@ -349,8 +351,8 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
    * b) the guest used a large mapping which we're faking
    * Either way, we need to satisfy the fault without
    * invoking the guest. */
    - kvmppc_mmu_map(vcpu, eaddr, gfn, gtlbe->tid,
    - gtlbe->word2);
    + kvmppc_mmu_map(vcpu, eaddr, gpaddr, gtlbe->tid,
    + gtlbe->word2, get_tlb_bytes(gtlbe));
    } else {
    /* Guest mapped and leaped at non-RAM! */
    kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_MACHINE_CHECK);
    --
    1.6.0.3


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