[PATCH 4/5 v4] KVM: PPC: Alow kvmppc_get_last_inst() to fail
Alexander Graf
agraf at suse.de
Thu Jul 3 23:44:42 EST 2014
On 28.06.14 00:49, Mihai Caraman wrote:
> On book3e, guest last instruction is read on the exit path using load
> external pid (lwepx) dedicated instruction. This load operation may fail
> due to TLB eviction and execute-but-not-read entries.
>
> This patch lay down the path for an alternative solution to read the guest
> last instruction, by allowing kvmppc_get_lat_inst() function to fail.
> Architecture specific implmentations of kvmppc_load_last_inst() may read
> last guest instruction and instruct the emulation layer to re-execute the
> guest in case of failure.
>
> Make kvmppc_get_last_inst() definition common between architectures.
>
> Signed-off-by: Mihai Caraman <mihai.caraman at freescale.com>
> ---
> v4:
> - these changes compile on book3s, please validate the functionality and
> do the necessary adaptations!
> - common declaration and enum for kvmppc_load_last_inst()
> - remove kvmppc_read_inst() in a preceding patch
>
> v3:
> - rework patch description
> - add common definition for kvmppc_get_last_inst()
> - check return values in book3s code
>
> v2:
> - integrated kvmppc_get_last_inst() in book3s code and checked build
> - addressed cosmetic feedback
>
> arch/powerpc/include/asm/kvm_book3s.h | 26 ------------------
> arch/powerpc/include/asm/kvm_booke.h | 5 ----
> arch/powerpc/include/asm/kvm_ppc.h | 24 +++++++++++++++++
> arch/powerpc/kvm/book3s.c | 11 ++++++++
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 17 ++++--------
> arch/powerpc/kvm/book3s_paired_singles.c | 38 +++++++++++++++++----------
> arch/powerpc/kvm/book3s_pr.c | 45 ++++++++++++++++++++++++--------
> arch/powerpc/kvm/booke.c | 3 +++
> arch/powerpc/kvm/e500_mmu_host.c | 6 +++++
> arch/powerpc/kvm/emulate.c | 18 ++++++++-----
> arch/powerpc/kvm/powerpc.c | 11 ++++++--
> 11 files changed, 128 insertions(+), 76 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> index ceb70aa..1300cd9 100644
> --- a/arch/powerpc/include/asm/kvm_book3s.h
> +++ b/arch/powerpc/include/asm/kvm_book3s.h
> @@ -276,32 +276,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu)
> return (kvmppc_get_msr(vcpu) & MSR_LE) != (MSR_KERNEL & MSR_LE);
> }
>
> -static inline u32 kvmppc_get_last_inst_internal(struct kvm_vcpu *vcpu, ulong pc)
> -{
> - /* Load the instruction manually if it failed to do so in the
> - * exit path */
> - if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)
> - kvmppc_ld(vcpu, &pc, sizeof(u32), &vcpu->arch.last_inst, false);
> -
> - return kvmppc_need_byteswap(vcpu) ? swab32(vcpu->arch.last_inst) :
> - vcpu->arch.last_inst;
> -}
> -
> -static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)
> -{
> - return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu));
> -}
> -
> -/*
> - * Like kvmppc_get_last_inst(), but for fetching a sc instruction.
> - * Because the sc instruction sets SRR0 to point to the following
> - * instruction, we have to fetch from pc - 4.
> - */
> -static inline u32 kvmppc_get_last_sc(struct kvm_vcpu *vcpu)
> -{
> - return kvmppc_get_last_inst_internal(vcpu, kvmppc_get_pc(vcpu) - 4);
> -}
> -
> static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu *vcpu)
> {
> return vcpu->arch.fault_dar;
> diff --git a/arch/powerpc/include/asm/kvm_booke.h b/arch/powerpc/include/asm/kvm_booke.h
> index c7aed61..cbb1990 100644
> --- a/arch/powerpc/include/asm/kvm_booke.h
> +++ b/arch/powerpc/include/asm/kvm_booke.h
> @@ -69,11 +69,6 @@ static inline bool kvmppc_need_byteswap(struct kvm_vcpu *vcpu)
> return false;
> }
>
> -static inline u32 kvmppc_get_last_inst(struct kvm_vcpu *vcpu)
> -{
> - return vcpu->arch.last_inst;
> -}
> -
> static inline void kvmppc_set_ctr(struct kvm_vcpu *vcpu, ulong val)
> {
> vcpu->arch.ctr = val;
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index e2fd5a1..ec326c8 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -47,6 +47,11 @@ enum emulation_result {
> EMULATE_EXIT_USER, /* emulation requires exit to user-space */
> };
>
> +enum instruction_type {
> + INST_GENERIC,
> + INST_SC, /* system call */
> +};
> +
> extern int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
> extern int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
> extern void kvmppc_handler_highmem(void);
> @@ -62,6 +67,9 @@ extern int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
> u64 val, unsigned int bytes,
> int is_default_endian);
>
> +extern int kvmppc_load_last_inst(struct kvm_vcpu *vcpu,
> + enum instruction_type type, u32 *inst);
> +
> extern int kvmppc_emulate_instruction(struct kvm_run *run,
> struct kvm_vcpu *vcpu);
> extern int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu);
> @@ -234,6 +242,22 @@ struct kvmppc_ops {
> extern struct kvmppc_ops *kvmppc_hv_ops;
> extern struct kvmppc_ops *kvmppc_pr_ops;
>
> +static inline int kvmppc_get_last_inst(struct kvm_vcpu *vcpu,
> + enum instruction_type type, u32 *inst)
> +{
> + int ret = EMULATE_DONE;
> +
> + /* Load the instruction manually if it failed to do so in the
> + * exit path */
> + if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED)
> + ret = kvmppc_load_last_inst(vcpu, type, &vcpu->arch.last_inst);
> +
> + *inst = kvmppc_need_byteswap(vcpu) ? swab32(vcpu->arch.last_inst) :
> + vcpu->arch.last_inst;
We swap needlessly when the translation failed, but I don't think it
really hurts.
> +
> + return ret;
So here we just return the return value of kvmppc_load_last_inst() ...
> +}
> +
> static inline bool is_kvmppc_hv_enabled(struct kvm *kvm)
> {
> return kvm->arch.kvm_ops == kvmppc_hv_ops;
> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
> index bd75902..c17f101 100644
> --- a/arch/powerpc/kvm/book3s.c
> +++ b/arch/powerpc/kvm/book3s.c
> @@ -467,6 +467,17 @@ mmio:
> }
> EXPORT_SYMBOL_GPL(kvmppc_ld);
>
> +int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,
> + u32 *inst)
> +{
> + ulong pc = kvmppc_get_pc(vcpu);
> +
> + if (type == INST_SC)
> + pc -= 4;
> + return kvmppc_ld(vcpu, &pc, sizeof(u32), &vcpu->arch.last_inst, false);
... which simply returns the return value of kvmppc_ld(). However,
kvmppc_ld() returns -ENOENT when it doesn't find a translation. We need
to convert the return value space of kvmppc_ld() into an EMULATE_ name
space that makes sense for this function.
How about something like
r = kvmppc_ld();
if (r == EMULATE_DONE)
return r;
else
return EMULATE_AGAIN;
That way we make sure that we tell the caller only "yes, all is good" or
"please go back into the guest".
> +}
> +EXPORT_SYMBOL_GPL(kvmppc_load_last_inst);
> +
> int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
> {
> return 0;
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 8056107..2c2b7ad 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -530,21 +530,14 @@ static int instruction_is_store(unsigned int instr)
> static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu,
> unsigned long gpa, gva_t ea, int is_store)
> {
> - int ret;
> u32 last_inst;
> - unsigned long srr0 = kvmppc_get_pc(vcpu);
>
> - /* We try to load the last instruction. We don't let
> - * emulate_instruction do it as it doesn't check what
> - * kvmppc_ld returns.
> + /*
> * If we fail, we just return to the guest and try executing it again.
> */
> - if (vcpu->arch.last_inst == KVM_INST_FETCH_FAILED) {
> - ret = kvmppc_ld(vcpu, &srr0, sizeof(u32), &last_inst, false);
> - if (ret != EMULATE_DONE || last_inst == KVM_INST_FETCH_FAILED)
> - return RESUME_GUEST;
> - vcpu->arch.last_inst = last_inst;
> - }
> + if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
> + EMULATE_DONE)
> + return RESUME_GUEST;
This looks great.
>
> /*
> * WARNING: We do not know for sure whether the instruction we just
> @@ -558,7 +551,7 @@ static int kvmppc_hv_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu,
> * we just return and retry the instruction.
> */
>
> - if (instruction_is_store(kvmppc_get_last_inst(vcpu)) != !!is_store)
> + if (instruction_is_store(last_inst) != !!is_store)
> return RESUME_GUEST;
>
> /*
> diff --git a/arch/powerpc/kvm/book3s_paired_singles.c b/arch/powerpc/kvm/book3s_paired_singles.c
> index 6c8011f..bfb8035 100644
> --- a/arch/powerpc/kvm/book3s_paired_singles.c
> +++ b/arch/powerpc/kvm/book3s_paired_singles.c
> @@ -639,26 +639,36 @@ static int kvmppc_ps_one_in(struct kvm_vcpu *vcpu, bool rc,
>
> int kvmppc_emulate_paired_single(struct kvm_run *run, struct kvm_vcpu *vcpu)
> {
> - u32 inst = kvmppc_get_last_inst(vcpu);
> + u32 inst;
> enum emulation_result emulated = EMULATE_DONE;
> + int ax_rd, ax_ra, ax_rb, ax_rc;
> + short full_d;
> + u64 *fpr_d, *fpr_a, *fpr_b, *fpr_c;
>
> - int ax_rd = inst_get_field(inst, 6, 10);
> - int ax_ra = inst_get_field(inst, 11, 15);
> - int ax_rb = inst_get_field(inst, 16, 20);
> - int ax_rc = inst_get_field(inst, 21, 25);
> - short full_d = inst_get_field(inst, 16, 31);
> -
> - u64 *fpr_d = &VCPU_FPR(vcpu, ax_rd);
> - u64 *fpr_a = &VCPU_FPR(vcpu, ax_ra);
> - u64 *fpr_b = &VCPU_FPR(vcpu, ax_rb);
> - u64 *fpr_c = &VCPU_FPR(vcpu, ax_rc);
> -
> - bool rcomp = (inst & 1) ? true : false;
> - u32 cr = kvmppc_get_cr(vcpu);
> + bool rcomp;
> + u32 cr;
> #ifdef DEBUG
> int i;
> #endif
>
> + emulated = kvmppc_get_last_inst(vcpu, INST_GENERIC, &inst);
> + if (emulated != EMULATE_DONE)
> + return emulated;
Here we're already leaking the "emulated" return value into the caller.
The caller in this chain should know what EMULATE_AGAIN means, so with
the change above we're safe.
> +
> + ax_rd = inst_get_field(inst, 6, 10);
> + ax_ra = inst_get_field(inst, 11, 15);
> + ax_rb = inst_get_field(inst, 16, 20);
> + ax_rc = inst_get_field(inst, 21, 25);
> + full_d = inst_get_field(inst, 16, 31);
> +
> + fpr_d = &VCPU_FPR(vcpu, ax_rd);
> + fpr_a = &VCPU_FPR(vcpu, ax_ra);
> + fpr_b = &VCPU_FPR(vcpu, ax_rb);
> + fpr_c = &VCPU_FPR(vcpu, ax_rc);
> +
> + rcomp = (inst & 1) ? true : false;
> + cr = kvmppc_get_cr(vcpu);
> +
> if (!kvmppc_inst_is_paired_single(vcpu, inst))
> return EMULATE_FAIL;
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index d247d88..7bbaeec 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -970,15 +970,24 @@ int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
> {
> enum emulation_result er;
> ulong flags;
> + u32 last_inst;
> + int emul;
>
> program_interrupt:
> flags = vcpu->arch.shadow_srr1 & 0x1f0000ull;
>
> + emul = kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
> + if (emul != EMULATE_DONE) {
> + r = RESUME_GUEST;
Yes, this looks good.
> + break;
> + }
> +
> if (kvmppc_get_msr(vcpu) & MSR_PR) {
> #ifdef EXIT_DEBUG
> - printk(KERN_INFO "Userspace triggered 0x700 exception at 0x%lx (0x%x)\n", kvmppc_get_pc(vcpu), kvmppc_get_last_inst(vcpu));
> + pr_info("Userspace triggered 0x700 exception at\n 0x%lx (0x%x)\n",
> + kvmppc_get_pc(vcpu), last_inst);
> #endif
> - if ((kvmppc_get_last_inst(vcpu) & 0xff0007ff) !=
> + if ((last_inst & 0xff0007ff) !=
> (INS_DCBZ & 0xfffffff7)) {
> kvmppc_core_queue_program(vcpu, flags);
> r = RESUME_GUEST;
> @@ -997,7 +1006,7 @@ program_interrupt:
> break;
> case EMULATE_FAIL:
> printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
> - __func__, kvmppc_get_pc(vcpu), kvmppc_get_last_inst(vcpu));
> + __func__, kvmppc_get_pc(vcpu), last_inst);
> kvmppc_core_queue_program(vcpu, flags);
> r = RESUME_GUEST;
> break;
> @@ -1014,8 +1023,25 @@ program_interrupt:
> break;
> }
> case BOOK3S_INTERRUPT_SYSCALL:
> + {
> + u32 last_sc;
> + int emul;
> +
> + /* Get last sc for papr */
> + if (vcpu->arch.papr_enabled) {
> + /*
> + * The sc instuction sets SRR0 to point to the next inst
> + */
> + emul = kvmppc_get_last_inst(vcpu, INST_SC, &last_sc);
> + if (emul != EMULATE_DONE) {
> + kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) - 4);
> + r = RESUME_GUEST;
This also looks good :).
> + break;
> + }
> + }
> +
> if (vcpu->arch.papr_enabled &&
> - (kvmppc_get_last_sc(vcpu) == 0x44000022) &&
> + (last_sc == 0x44000022) &&
> !(kvmppc_get_msr(vcpu) & MSR_PR)) {
> /* SC 1 papr hypercalls */
> ulong cmd = kvmppc_get_gpr(vcpu, 3);
> @@ -1060,13 +1086,13 @@ program_interrupt:
> r = RESUME_GUEST;
> }
> break;
> + }
> case BOOK3S_INTERRUPT_FP_UNAVAIL:
> case BOOK3S_INTERRUPT_ALTIVEC:
> case BOOK3S_INTERRUPT_VSX:
> {
> int ext_msr = 0;
> int emul;
> - ulong pc;
> u32 last_inst;
>
> if (!(vcpu->arch.hflags & BOOK3S_HFLAG_PAIRED_SINGLE)) {
> @@ -1090,9 +1116,7 @@ program_interrupt:
> break;
> }
>
> - pc = kvmppc_get_pc(vcpu);
> - last_inst = kvmppc_get_last_inst(vcpu);
> - emul = kvmppc_ld(vcpu, &pc, sizeof(u32), &last_inst, false);
> + emul = kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
> if (emul == EMULATE_DONE) {
> /* we need to emulate this instruction */
> goto program_interrupt;
> @@ -1105,9 +1129,8 @@ program_interrupt:
> }
> case BOOK3S_INTERRUPT_ALIGNMENT:
> {
> - ulong pc = kvmppc_get_pc(vcpu);
> - u32 last_inst = kvmppc_get_last_inst(vcpu);
> - int emul = kvmppc_ld(vcpu, &pc, sizeof(u32), &last_inst, false);
> + u32 last_inst;
> + int emul = kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
>
> if (emul == EMULATE_DONE) {
> u32 dsisr;
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index ab62109..34a42b9 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -752,6 +752,9 @@ static int emulation_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
> * they were actually modified by emulation. */
> return RESUME_GUEST_NV;
>
> + case EMULATE_AGAIN:
> + return RESUME_GUEST;
Yup :).
> +
> case EMULATE_DO_DCR:
> run->exit_reason = KVM_EXIT_DCR;
> return RESUME_HOST;
> diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
> index dd2cc03..4b4e8d6 100644
> --- a/arch/powerpc/kvm/e500_mmu_host.c
> +++ b/arch/powerpc/kvm/e500_mmu_host.c
> @@ -606,6 +606,12 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 eaddr, gpa_t gpaddr,
> }
> }
>
> +int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,
> + u32 *instr)
> +{
> + return EMULATE_FAIL;
This should be EMULATE_AGAIN, no?
> +}
> +
> /************* MMU Notifiers *************/
>
> int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
> index da86d9b..c5c64b6 100644
> --- a/arch/powerpc/kvm/emulate.c
> +++ b/arch/powerpc/kvm/emulate.c
> @@ -224,19 +224,25 @@ static int kvmppc_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
> * from opcode tables in the future. */
> int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
> {
> - u32 inst = kvmppc_get_last_inst(vcpu);
> - int ra = get_ra(inst);
> - int rs = get_rs(inst);
> - int rt = get_rt(inst);
> - int sprn = get_sprn(inst);
> - enum emulation_result emulated = EMULATE_DONE;
> + u32 inst;
> + int ra, rs, rt, sprn;
> + enum emulation_result emulated;
> int advance = 1;
>
> /* this default type might be overwritten by subcategories */
> kvmppc_set_exit_type(vcpu, EMULATED_INST_EXITS);
>
> + emulated = kvmppc_get_last_inst(vcpu, false, &inst);
> + if (emulated != EMULATE_DONE)
> + return emulated;
and here we're leaking again ;). It's perfectly fine to do so, but let's
make sure we don't leak -ENOENT :). So here too the fix above should
make things work.
Alex
> +
> pr_debug("Emulating opcode %d / %d\n", get_op(inst), get_xop(inst));
>
> + ra = get_ra(inst);
> + rs = get_rs(inst);
> + rt = get_rt(inst);
> + sprn = get_sprn(inst);
> +
> switch (get_op(inst)) {
> case OP_TRAP:
> #ifdef CONFIG_PPC_BOOK3S
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 7efc2b7..da54e4b 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -261,6 +261,9 @@ int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu)
> * actually modified. */
> r = RESUME_GUEST_NV;
> break;
> + case EMULATE_AGAIN:
> + r = RESUME_GUEST;
> + break;
> case EMULATE_DO_MMIO:
> run->exit_reason = KVM_EXIT_MMIO;
> /* We must reload nonvolatiles because "update" load/store
> @@ -270,11 +273,15 @@ int kvmppc_emulate_mmio(struct kvm_run *run, struct kvm_vcpu *vcpu)
> r = RESUME_HOST_NV;
> break;
> case EMULATE_FAIL:
> + {
> + u32 last_inst;
> +
> + kvmppc_get_last_inst(vcpu, false, &last_inst);
> /* XXX Deliver Program interrupt to guest. */
> - printk(KERN_EMERG "%s: emulation failed (%08x)\n", __func__,
> - kvmppc_get_last_inst(vcpu));
> + pr_emerg("%s: emulation failed (%08x)\n", __func__, last_inst);
> r = RESUME_HOST;
> break;
> + }
> default:
> WARN_ON(1);
> r = RESUME_GUEST;
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