On Mon, Oct 08, 2018 at 04:31:03PM +1100, Paul Mackerras wrote:
> This starts the process of adding the code to support nested HV-style
> virtualization. It defines a new H_SET_PARTITION_TABLE hypercall which
> a nested hypervisor can use to set the base address and size of a
> partition table in its memory (analogous to the PTCR register).
> On the host (level 0 hypervisor) side, the H_SET_PARTITION_TABLE
> hypercall from the guest is handled by code that saves the virtual
> PTCR value for the guest.
>
> This also adds code for creating and destroying nested guests and for
> reading the partition table entry for a nested guest from L1 memory.
> Each nested guest has its own shadow LPID value, different in general
> from the LPID value used by the nested hypervisor to refer to it. The
> shadow LPID value is allocated at nested guest creation time.
>
> Nested hypervisor functionality is only available for a radix guest,
> which therefore means a radix host on a POWER9 (or later) processor.
>
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
> arch/powerpc/include/asm/hvcall.h | 5 +
> arch/powerpc/include/asm/kvm_book3s.h | 10 +-
> arch/powerpc/include/asm/kvm_book3s_64.h | 33 ++++
> arch/powerpc/include/asm/kvm_book3s_asm.h | 3 +
> arch/powerpc/include/asm/kvm_host.h | 5 +
> arch/powerpc/kvm/Makefile | 3 +-
> arch/powerpc/kvm/book3s_hv.c | 31 ++-
> arch/powerpc/kvm/book3s_hv_nested.c | 301 ++++++++++++++++++++++++++++++
> 8 files changed, 384 insertions(+), 7 deletions(-)
> create mode 100644 arch/powerpc/kvm/book3s_hv_nested.c
>
> diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
> index a0b17f9..c95c651 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -322,6 +322,11 @@
> #define H_GET_24X7_DATA 0xF07C
> #define H_GET_PERF_COUNTER_INFO 0xF080
>
> +/* Platform-specific hcalls used for nested HV KVM */
> +#define H_SET_PARTITION_TABLE 0xF800
> +#define H_ENTER_NESTED 0xF804
> +#define H_TLB_INVALIDATE 0xF808
> +
> /* Values for 2nd argument to H_SET_MODE */
> #define H_SET_MODE_RESOURCE_SET_CIABR 1
> #define H_SET_MODE_RESOURCE_SET_DAWR 2
> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> index 91c9779..43f212e 100644
> --- a/arch/powerpc/include/asm/kvm_book3s.h
> +++ b/arch/powerpc/include/asm/kvm_book3s.h
> @@ -274,6 +274,13 @@ static inline void kvmppc_save_tm_sprs(struct kvm_vcpu *vcpu) {}
> static inline void kvmppc_restore_tm_sprs(struct kvm_vcpu *vcpu) {}
> #endif
>
> +long kvmhv_nested_init(void);
> +void kvmhv_nested_exit(void);
> +void kvmhv_vm_nested_init(struct kvm *kvm);
> +long kvmhv_set_partition_table(struct kvm_vcpu *vcpu);
> +void kvmhv_set_ptbl_entry(unsigned int lpid, u64 dw0, u64 dw1);
> +void kvmhv_release_all_nested(struct kvm *kvm);
> +
> void kvmppc_giveup_fac(struct kvm_vcpu *vcpu, ulong fac);
>
> extern int kvm_irq_bypass;
> @@ -387,9 +394,6 @@ extern int kvmppc_h_logical_ci_store(struct kvm_vcpu *vcpu);
> /* TO = 31 for unconditional trap */
> #define INS_TW 0x7fe00008
>
> -/* LPIDs we support with this build -- runtime limit may be lower */
> -#define KVMPPC_NR_LPIDS (LPID_RSVD + 1)
> -
> #define SPLIT_HACK_MASK 0xff000000
> #define SPLIT_HACK_OFFS 0xfb000000
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
> index 5c0e2d9..6d67b6a 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_64.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_64.h
> @@ -23,6 +23,39 @@
> #include <linux/string.h>
> #include <asm/bitops.h>
> #include <asm/book3s/64/mmu-hash.h>
> +#include <asm/cpu_has_feature.h>
> +
> +#ifdef CONFIG_PPC_PSERIES
> +static inline bool kvmhv_on_pseries(void)
> +{
> + return !cpu_has_feature(CPU_FTR_HVMODE);
> +}
> +#else
> +static inline bool kvmhv_on_pseries(void)
> +{
> + return false;
> +}
> +#endif
> +
> +/*
> + * Structure for a nested guest, that is, for a guest that is managed by
> + * one of our guests.
> + */
> +struct kvm_nested_guest {
> + struct kvm *l1_host; /* L1 VM that owns this nested guest */
> + int l1_lpid; /* lpid L1 guest thinks this guest is */
> + int shadow_lpid; /* real lpid of this nested guest */
> + pgd_t *shadow_pgtable; /* our page table for this guest */
> + u64 l1_gr_to_hr; /* L1's addr of part'n-scoped table */
> + u64 process_table; /* process table entry for this guest */
> + long refcnt; /* number of pointers to this struct */
> + struct mutex tlb_lock; /* serialize page faults and tlbies */
> + struct kvm_nested_guest *next;
> +};
> +
> +struct kvm_nested_guest *kvmhv_get_nested(struct kvm *kvm, int l1_lpid,
> + bool create);
> +void kvmhv_put_nested(struct kvm_nested_guest *gp);
>
> /* Power architecture requires HPT is at least 256kiB, at most 64TiB */
> #define PPC_MIN_HPT_ORDER 18
> diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
> index d978fdf..eb3ba63 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_asm.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
> @@ -25,6 +25,9 @@
> #define XICS_MFRR 0xc
> #define XICS_IPI 2 /* interrupt source # for IPIs */
>
> +/* LPIDs we support with this build -- runtime limit may be lower */
> +#define KVMPPC_NR_LPIDS (LPID_RSVD + 1)
> +
> /* Maximum number of threads per physical core */
> #define MAX_SMT_THREADS 8
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index c9cc42f..c35d4f2 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -46,6 +46,7 @@
> #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> #include <asm/kvm_book3s_asm.h> /* for MAX_SMT_THREADS */
> #define KVM_MAX_VCPU_ID (MAX_SMT_THREADS * KVM_MAX_VCORES)
> +#define KVM_MAX_NESTED_GUESTS KVMPPC_NR_LPIDS
>
> #else
> #define KVM_MAX_VCPU_ID KVM_MAX_VCPUS
> @@ -287,6 +288,7 @@ struct kvm_arch {
> u8 radix;
> u8 fwnmi_enabled;
> bool threads_indep;
> + bool nested_enable;
> pgd_t *pgtable;
> u64 process_table;
> struct dentry *debugfs_dir;
> @@ -312,6 +314,9 @@ struct kvm_arch {
> #endif
> struct kvmppc_ops *kvm_ops;
> #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> + u64 l1_ptcr;
> + int max_nested_lpid;
> + struct kvm_nested_guest *nested_guests[KVM_MAX_NESTED_GUESTS];
> /* This array can grow quite large, keep it at the end */
> struct kvmppc_vcore *vcores[KVM_MAX_VCORES];
> #endif
> diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
> index f872c04..e814f40 100644
> --- a/arch/powerpc/kvm/Makefile
> +++ b/arch/powerpc/kvm/Makefile
> @@ -75,7 +75,8 @@ kvm-hv-y += \
> book3s_hv.o \
> book3s_hv_interrupts.o \
> book3s_64_mmu_hv.o \
> - book3s_64_mmu_radix.o
> + book3s_64_mmu_radix.o \
> + book3s_hv_nested.o
>
> kvm-hv-$(CONFIG_PPC_TRANSACTIONAL_MEM) += \
> book3s_hv_tm.o
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 8425d72..4c72f2f 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -934,6 +934,19 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> if (ret == H_TOO_HARD)
> return RESUME_HOST;
> break;
> +
> + case H_SET_PARTITION_TABLE:
> + ret = H_FUNCTION;
> + if (vcpu->kvm->arch.nested_enable)
> + ret = kvmhv_set_partition_table(vcpu);
> + break;
> + case H_ENTER_NESTED:
> + ret = H_FUNCTION;
> + break;
> + case H_TLB_INVALIDATE:
> + ret = H_FUNCTION;
> + break;
> +
> default:
> return RESUME_HOST;
> }
> @@ -4153,8 +4166,7 @@ void kvmppc_setup_partition_table(struct kvm *kvm)
> __pa(kvm->arch.pgtable) | RADIX_PGD_INDEX_SIZE;
> dw1 = PATB_GR | kvm->arch.process_table;
> }
> -
> - mmu_partition_table_set_entry(kvm->arch.lpid, dw0, dw1);
> + kvmhv_set_ptbl_entry(kvm->arch.lpid, dw0, dw1);
> }
>
> /*
> @@ -4250,6 +4262,10 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
> /* Must be called with kvm->lock held and mmu_ready = 0 and no vcpus running */
> int kvmppc_switch_mmu_to_hpt(struct kvm *kvm)
> {
> + if (kvm->arch.nested_enable) {
> + kvm->arch.nested_enable = false;
> + kvmhv_release_all_nested(kvm);
> + }
> kvmppc_free_radix(kvm);
> kvmppc_update_lpcr(kvm, LPCR_VPM1,
> LPCR_VPM1 | LPCR_UPRT | LPCR_GTSE | LPCR_HR);
> @@ -4370,6 +4386,8 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm)
>
> kvmppc_alloc_host_rm_ops();
>
> + kvmhv_vm_nested_init(kvm);
> +
> /*
> * Since we don't flush the TLB when tearing down a VM,
> * and this lpid might have previously been used,
> @@ -4513,8 +4531,10 @@ static void kvmppc_core_destroy_vm_hv(struct kvm *kvm)
>
> /* Perform global invalidation and return lpid to the pool */
> if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> + if (kvm->arch.nested_enable)
> + kvmhv_release_all_nested(kvm);
> kvm->arch.process_table = 0;
> - kvmppc_setup_partition_table(kvm);
> + kvmhv_set_ptbl_entry(kvm->arch.lpid, 0, 0);
> }
> kvmppc_free_lpid(kvm->arch.lpid);
>
> @@ -4985,6 +5005,10 @@ static int kvmppc_book3s_init_hv(void)
> if (r < 0)
> return -ENODEV;
>
> + r = kvmhv_nested_init();
> + if (r)
> + return r;
> +
> r = kvm_init_subcore_bitmap();
> if (r)
> return r;
> @@ -5043,6 +5067,7 @@ static void kvmppc_book3s_exit_hv(void)
> if (kvmppc_radix_possible())
> kvmppc_radix_exit();
> kvmppc_hv_ops = NULL;
> + kvmhv_nested_exit();
> }
>
> module_init(kvmppc_book3s_init_hv);
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> new file mode 100644
> index 0000000..32782624
> --- /dev/null
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -0,0 +1,301 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright IBM Corporation, 2018
> + * Authors Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> + * Paul Mackerras <paulus@xxxxxxxxxx>
> + *
> + * Description: KVM functions specific to running nested KVM-HV guests
> + * on Book3S processors (specifically POWER9 and later).
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/kvm_host.h>
> +
> +#include <asm/kvm_ppc.h>
> +#include <asm/mmu.h>
> +#include <asm/pgtable.h>
> +#include <asm/pgalloc.h>
> +
> +static struct patb_entry *pseries_partition_tb;
> +
> +static void kvmhv_update_ptbl_cache(struct kvm_nested_guest *gp);
> +
> +long kvmhv_nested_init(void)
> +{
> + long int ptb_order;
> + unsigned long ptcr;
> + long rc;
> +
> + if (!kvmhv_on_pseries())
> + return 0;
> + if (!radix_enabled())
> + return -ENODEV;
> +
> + /* find log base 2 of KVMPPC_NR_LPIDS, rounding up */
> + ptb_order = __ilog2(KVMPPC_NR_LPIDS - 1) + 1;
> + if (ptb_order < 8)
> + ptb_order = 8;
> + pseries_partition_tb = kmalloc(sizeof(struct patb_entry) << ptb_order,
> + GFP_KERNEL);
> + if (!pseries_partition_tb) {
> + pr_err("kvm-hv: failed to allocated nested partition table\n");
> + return -ENOMEM;
> + }
> +
> + ptcr = __pa(pseries_partition_tb) | (ptb_order - 8);
> + rc = plpar_hcall_norets(H_SET_PARTITION_TABLE, ptcr);
> + if (rc != H_SUCCESS) {
> + pr_err("kvm-hv: Parent hypervisor does not support nesting (rc=%ld)\n",
> + rc);
> + kfree(pseries_partition_tb);
> + pseries_partition_tb = NULL;
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> +void kvmhv_nested_exit(void)
> +{
> + /*
> + * N.B. the kvmhv_on_pseries() test is there because it enables
> + * the compiler to remove the call to plpar_hcall_norets()
> + * when CONFIG_PPC_PSERIES=n.
> + */
> + if (kvmhv_on_pseries() && pseries_partition_tb) {
> + plpar_hcall_norets(H_SET_PARTITION_TABLE, 0);
> + kfree(pseries_partition_tb);
> + pseries_partition_tb = NULL;
> + }
> +}
> +
> +void kvmhv_set_ptbl_entry(unsigned int lpid, u64 dw0, u64 dw1)
> +{
> + if (cpu_has_feature(CPU_FTR_HVMODE)) {
> + mmu_partition_table_set_entry(lpid, dw0, dw1);
> + } else {
> + pseries_partition_tb[lpid].patb0 = cpu_to_be64(dw0);
> + pseries_partition_tb[lpid].patb1 = cpu_to_be64(dw1);
To double check my understanding: we don't need any locking on pseries
on pseries_partition_tb, because the allocation of lpids is properly
synchronized, so we assume that code which knows about an lpid "owns"
that slot in the table. Is that right?
> + }
> +}
> +
> +static void kvmhv_set_nested_ptbl(struct kvm_nested_guest *gp)
> +{
> + unsigned long dw0;
> +
> + dw0 = PATB_HR | radix__get_tree_size() |
> + __pa(gp->shadow_pgtable) | RADIX_PGD_INDEX_SIZE;
> + kvmhv_set_ptbl_entry(gp->shadow_lpid, dw0, gp->process_table);
> +}
> +
> +void kvmhv_vm_nested_init(struct kvm *kvm)
> +{
> + kvm->arch.max_nested_lpid = -1;
> +}
> +
> +/*
> + * Handle the H_SET_PARTITION_TABLE hcall.
> + * r4 = guest real address of partition table + log_2(size) - 12
> + * (formatted as for the PTCR).
> + */
> +long kvmhv_set_partition_table(struct kvm_vcpu *vcpu)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + unsigned long ptcr = kvmppc_get_gpr(vcpu, 4);
> + int srcu_idx;
> + long ret = H_SUCCESS;
> +
> + srcu_idx = srcu_read_lock(&kvm->srcu);
> + /*
> + * Limit the partition table to 4096 entries (because that's what
> + * hardware supports), and check the base address.
> + */
> + if ((ptcr & PRTS_MASK) > 12 - 8 ||
> + !kvm_is_visible_gfn(vcpu->kvm, (ptcr & PRTB_MASK) >> PAGE_SHIFT))
> + ret = H_PARAMETER;
Note there's a subtle dependency on 64k page size here, since you only
validate the table's base address.
> + srcu_read_unlock(&kvm->srcu, srcu_idx);
> + if (ret == H_SUCCESS)
> + kvm->arch.l1_ptcr = ptcr;
> + return ret;
> +}
> +
> +/*
> + * Reload the partition table entry for a guest.
> + * Caller must hold gp->tlb_lock.
> + */
> +static void kvmhv_update_ptbl_cache(struct kvm_nested_guest *gp)
> +{
> + int ret;
> + struct patb_entry ptbl_entry;
> + unsigned long ptbl_addr;
> + struct kvm *kvm = gp->l1_host;
> +
> + ret = -EFAULT;
> + ptbl_addr = (kvm->arch.l1_ptcr & PRTB_MASK) + (gp->l1_lpid << 4);
> + if (gp->l1_lpid < (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 8)))
> + ret = kvm_read_guest(kvm, ptbl_addr,
> + &ptbl_entry, sizeof(ptbl_entry));
> + if (ret) {
> + gp->l1_gr_to_hr = 0;
> + gp->process_table = 0;
> + } else {
> + gp->l1_gr_to_hr = be64_to_cpu(ptbl_entry.patb0);
> + gp->process_table = be64_to_cpu(ptbl_entry.patb1);
> + }
> + kvmhv_set_nested_ptbl(gp);
> +}
> +
> +struct kvm_nested_guest *kvmhv_alloc_nested(struct kvm *kvm, unsigned int lpid)
> +{
> + struct kvm_nested_guest *gp;
> + long shadow_lpid;
> +
> + gp = kzalloc(sizeof(*gp), GFP_KERNEL);
> + if (!gp)
> + return NULL;
> + gp->l1_host = kvm;
> + gp->l1_lpid = lpid;
> + mutex_init(&gp->tlb_lock);
> + gp->shadow_pgtable = pgd_alloc(kvm->mm);
> + if (!gp->shadow_pgtable)
> + goto out_free;
> + shadow_lpid = kvmppc_alloc_lpid();
> + if (shadow_lpid < 0)
> + goto out_free2;
> + gp->shadow_lpid = shadow_lpid;
> +
> + return gp;
> +
> + out_free2:
> + pgd_free(kvm->mm, gp->shadow_pgtable);
> + out_free:
> + kfree(gp);
> + return NULL;
> +}
> +
> +/*
> + * Free up any resources allocated for a nested guest.
> + */
> +static void kvmhv_release_nested(struct kvm_nested_guest *gp)
> +{
> + kvmhv_set_ptbl_entry(gp->shadow_lpid, 0, 0);
> + kvmppc_free_lpid(gp->shadow_lpid);
> + if (gp->shadow_pgtable)
> + pgd_free(gp->l1_host->mm, gp->shadow_pgtable);
> + kfree(gp);
> +}
> +
> +static void kvmhv_remove_nested(struct kvm_nested_guest *gp)
> +{
> + struct kvm *kvm = gp->l1_host;
> + int lpid = gp->l1_lpid;
> + long ref;
> +
> + spin_lock(&kvm->mmu_lock);
> + if (gp == kvm->arch.nested_guests[lpid]) {
> + kvm->arch.nested_guests[lpid] = NULL;
> + if (lpid == kvm->arch.max_nested_lpid) {
> + while (--lpid >= 0 && !kvm->arch.nested_guests[lpid])
> + ;
> + kvm->arch.max_nested_lpid = lpid;
> + }
> + --gp->refcnt;
> + }
> + ref = gp->refcnt;
> + spin_unlock(&kvm->mmu_lock);
> + if (ref == 0)
> + kvmhv_release_nested(gp);
> +}
> +
> +/*
> + * Free up all nested resources allocated for this guest.
> + * This is called with no vcpus of the guest running, when
> + * switching the guest to HPT mode or when destroying the
> + * guest.
> + */
> +void kvmhv_release_all_nested(struct kvm *kvm)
> +{
> + int i;
> + struct kvm_nested_guest *gp;
> + struct kvm_nested_guest *freelist = NULL;
> +
> + spin_lock(&kvm->mmu_lock);
> + for (i = 0; i <= kvm->arch.max_nested_lpid; i++) {
> + gp = kvm->arch.nested_guests[i];
> + if (!gp)
> + continue;
> + kvm->arch.nested_guests[i] = NULL;
> + if (--gp->refcnt == 0) {
> + gp->next = freelist;
> + freelist = gp;
> + }
> + }
> + kvm->arch.max_nested_lpid = -1;
> + spin_unlock(&kvm->mmu_lock);
> + while ((gp = freelist) != NULL) {
> + freelist = gp->next;
> + kvmhv_release_nested(gp);
> + }
> +}
> +
> +/* caller must hold gp->tlb_lock */
> +void kvmhv_flush_nested(struct kvm_nested_guest *gp)
> +{
> + kvmhv_update_ptbl_cache(gp);
> + if (gp->l1_gr_to_hr == 0)
> + kvmhv_remove_nested(gp);
> +}
> +
> +struct kvm_nested_guest *kvmhv_get_nested(struct kvm *kvm, int l1_lpid,
> + bool create)
> +{
> + struct kvm_nested_guest *gp, *newgp;
> +
> + if (l1_lpid >= KVM_MAX_NESTED_GUESTS ||
> + l1_lpid >= (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 12 - 4)))
> + return NULL;
> +
> + spin_lock(&kvm->mmu_lock);
> + gp = kvm->arch.nested_guests[l1_lpid];
> + if (gp)
> + ++gp->refcnt;
> + spin_unlock(&kvm->mmu_lock);
> +
> + if (gp || !create)
> + return gp;
> +
> + newgp = kvmhv_alloc_nested(kvm, l1_lpid);
> + if (!newgp)
> + return NULL;
> + spin_lock(&kvm->mmu_lock);
> + if (kvm->arch.nested_guests[l1_lpid]) {
> + /* someone else beat us to it */
> + gp = kvm->arch.nested_guests[l1_lpid];
> + } else {
> + kvm->arch.nested_guests[l1_lpid] = newgp;
> + ++newgp->refcnt;
> + gp = newgp;
> + newgp = NULL;
> + if (l1_lpid > kvm->arch.max_nested_lpid)
> + kvm->arch.max_nested_lpid = l1_lpid;
> + }
> + ++gp->refcnt;
> + spin_unlock(&kvm->mmu_lock);
> +
> + if (newgp)
> + kvmhv_release_nested(newgp);
> +
> + return gp;
> +}
> +
> +void kvmhv_put_nested(struct kvm_nested_guest *gp)
> +{
> + struct kvm *kvm = gp->l1_host;
> + long ref;
> +
> + spin_lock(&kvm->mmu_lock);
> + ref = --gp->refcnt;
> + spin_unlock(&kvm->mmu_lock);
> + if (ref == 0)
> + kvmhv_release_nested(gp);
> +}
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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