Subject: Re: [PATCH v3 21/33] KVM: PPC: Book3S HV: Framework to handle HV Emulation Assist Interrupt

From: David Gibson <[email-masked]>
Date: Wed, 3 Oct 2018 15:13:01 +1000

On Tue, Oct 02, 2018 at 09:31:20PM +1000, Paul Mackerras wrote:
> From: Suraj Jitindar Singh <[email-masked]>
> 
> A HEAI (hypervisor emulation assistance interrupt) occurs when a
> hypervisor resource or instruction is used in a privileged but
> non-hypervisor state and the LPCR_EVIRT bit is set in LPCR.  When
> this occurs bit 45 is set in HSRR1.  Detect the occurrence of this,
> and if userspace has enabled the nested virtualization capability
> on the VM, then call the code to handle it accordingly.
> 
> With LPCR[EVIRT] set, we also get HEAI (without bit 45 set) for
> mfspr or mtspr to unimplemented SPR numbers.  For these accesses,
> we emulate the EVIRT=0 behaviour, which is to make the access
> a no-op for privileged software unless it is accessing SPR 0,
> 4, 5 or 6.  Problem-state accesses and accesses to SPR 0, 4, 5
> or 6 generate an illegal-instruction type program interrupt.
> 
> Reviewed-by: David Gibson <[email-masked]>
> Signed-off-by: Suraj Jitindar Singh <[email-masked]>
> Signed-off-by: Paul Mackerras <[email-masked]>

Do we still need this if we're moving to paravirt tlbie?

> ---
>  arch/powerpc/include/asm/kvm_book3s.h |  2 +
>  arch/powerpc/include/asm/reg.h        |  1 +
>  arch/powerpc/kvm/book3s_hv.c          | 87 ++++++++++++++++++++++-------------
>  arch/powerpc/kvm/book3s_hv_nested.c   | 55 ++++++++++++++++++++++
>  4 files changed, 113 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> index 093fd70..0a97446 100644
> --- a/arch/powerpc/include/asm/kvm_book3s.h
> +++ b/arch/powerpc/include/asm/kvm_book3s.h
> @@ -287,6 +287,8 @@ void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr);
>  void kvmhv_restore_hv_return_state(struct kvm_vcpu *vcpu,
>  				   struct hv_guest_state *hr);
>  long int kvmhv_nested_page_fault(struct kvm_vcpu *vcpu);
> +int kvmhv_emulate_priv(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +			unsigned int instr);
>  
>  void kvmppc_giveup_fac(struct kvm_vcpu *vcpu, ulong fac);
>  
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index 6fda746..9c42abf 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -456,6 +456,7 @@
>  #define   LPCR_HVICE		ASM_CONST(0x0000000000000002)      /* P9: HV interrupt enable */
>  #define   LPCR_HDICE		ASM_CONST(0x0000000000000001)      /* Hyp Decr enable (HV,PR,EE) */
>  #define   LPCR_UPRT		ASM_CONST(0x0000000000400000)      /* Use Process Table (ISA 3) */
> +#define   LPCR_EVIRT		ASM_CONST(0x0000000000200000)      /* Enhanced Virtualisation */
>  #define   LPCR_HR		ASM_CONST(0x0000000000100000)
>  #ifndef SPRN_LPID
>  #define SPRN_LPID	0x13F	/* Logical Partition Identifier */
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 134d7c7..b975683 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1027,30 +1027,6 @@ static int kvmppc_hcall_impl_hv(unsigned long cmd)
>  	return kvmppc_hcall_impl_hv_realmode(cmd);
>  }
>  
> -static int kvmppc_emulate_debug_inst(struct kvm_run *run,
> -					struct kvm_vcpu *vcpu)
> -{
> -	u32 last_inst;
> -
> -	if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
> -					EMULATE_DONE) {
> -		/*
> -		 * Fetch failed, so return to guest and
> -		 * try executing it again.
> -		 */
> -		return RESUME_GUEST;
> -	}
> -
> -	if (last_inst == KVMPPC_INST_SW_BREAKPOINT) {
> -		run->exit_reason = KVM_EXIT_DEBUG;
> -		run->debug.arch.address = kvmppc_get_pc(vcpu);
> -		return RESUME_HOST;
> -	} else {
> -		kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> -		return RESUME_GUEST;
> -	}
> -}
> -
>  static void do_nothing(void *x)
>  {
>  }
> @@ -1144,6 +1120,23 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu)
>  	return RESUME_GUEST;
>  }
>  
> +static int kvmhv_emulate_unknown_spr(struct kvm_vcpu *vcpu, u32 instr)
> +{
> +	u32 spr = get_sprn(instr);
> +
> +	/*
> +	 * In privileged state, access to unimplemented SPRs is a no-op
> +	 * except for SPR 0, 4, 5 and 6.  All other accesses get turned
> +	 * into illegal-instruction program interrupts.
> +	 */
> +	if ((vcpu->arch.shregs.msr & MSR_PR) ||
> +	    spr == 0 || (4 <= spr && spr <= 6))
> +		return EMULATE_FAIL;
> +
> +	kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
> +	return RESUME_GUEST;
> +}
> +
>  static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  				 struct task_struct *tsk)
>  {
> @@ -1260,19 +1253,49 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	 * to the guest. If guest debug is enabled, we need to check
>  	 * whether the instruction is a software breakpoint instruction.
>  	 * Accordingly return to Guest or Host.
> +	 * With LPCR[EVIRT] set, we also get these for accesses to
> +	 * unknown SPRs and for guests executing hypervisor privileged
> +	 * instructions.
>  	 */
>  	case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
> -		if (vcpu->arch.emul_inst != KVM_INST_FETCH_FAILED)
> -			vcpu->arch.last_inst = kvmppc_need_byteswap(vcpu) ?
> -				swab32(vcpu->arch.emul_inst) :
> -				vcpu->arch.emul_inst;
> -		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> -			r = kvmppc_emulate_debug_inst(run, vcpu);
> +	{
> +		u32 instr = vcpu->arch.emul_inst;
> +		unsigned long srr1_bit = SRR1_PROGILL;
> +
> +		vcpu->arch.last_inst = kvmppc_need_byteswap(vcpu) ?
> +			swab32(instr) : instr;
> +
> +		r = EMULATE_FAIL;
> +		if (vcpu->arch.shregs.msr & SRR1_PROGPRIV) {
> +			/*
> +			 * Tried to execute hypervisor privileged instruction
> +			 * or mtspr/mfspr on a hypervisor privileged SPR while
> +			 * MSR(HV | PR) == 0b00 -> Privileged but !HV state
> +			 */
> +			srr1_bit = SRR1_PROGPRIV;
> +			if (vcpu->kvm->arch.nested_enable)
> +				r = kvmhv_emulate_priv(run, vcpu, instr);
>  		} else {
> -			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
> +			/* Illegal instruction or unknown SPR access */
> +			if (instr == KVMPPC_INST_SW_BREAKPOINT &&
> +			    (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)) {
> +				run->exit_reason = KVM_EXIT_DEBUG;
> +				run->debug.arch.address = kvmppc_get_pc(vcpu);
> +				r = RESUME_HOST;
> +				break;
> +			}
> +			if ((instr & 0xfc0006fe) == PPC_INST_MFSPR)
> +				/* mfspr or mtspr to unknown SPR, may be noop */
> +				r = kvmhv_emulate_unknown_spr(vcpu, instr);
> +		}
> +		if (r == EMULATE_FAIL) {
> +			pr_debug("KVM: Couldn't emulate instruction 0x%.8x\n",
> +				 instr);
> +			kvmppc_core_queue_program(vcpu, srr1_bit);
>  			r = RESUME_GUEST;
>  		}
>  		break;
> +	}
>  	/*
>  	 * This occurs if the guest (kernel or userspace), does something that
>  	 * is prohibited by HFSCR.
> @@ -4612,7 +4635,7 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm)
>  	 */
>  	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
>  		lpcr &= ~LPCR_VPM0;
> -		lpcr |= LPCR_HVICE | LPCR_HEIC;
> +		lpcr |= LPCR_HVICE | LPCR_HEIC | LPCR_EVIRT;
>  
>  		/*
>  		 * If xive is enabled, we route 0x500 interrupts directly
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> index 4a381b4..f8f9fab 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -15,6 +15,7 @@
>  #include <asm/mmu.h>
>  #include <asm/pgtable.h>
>  #include <asm/pgalloc.h>
> +#include <asm/disassemble.h>
>  
>  static struct patb_entry *pseries_partition_tb;
>  
> @@ -515,3 +516,57 @@ long kvmhv_nested_page_fault(struct kvm_vcpu *vcpu)
>  {
>  	return RESUME_HOST;
>  }
> +
> +static int kvmhv_emulate_priv_mtspr(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +				    unsigned int instr)
> +{
> +	return EMULATE_FAIL;
> +}
> +
> +static int kvmhv_emulate_priv_mfspr(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +				    unsigned int instr)
> +{
> +	return EMULATE_FAIL;
> +}
> +
> +static int kvmhv_emulate_priv_op_31(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +				    unsigned int instr)
> +{
> +	return EMULATE_FAIL;
> +}
> +
> +static int kvmhv_emulate_priv_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +				  unsigned int instr)
> +{
> +	return EMULATE_FAIL;
> +}
> +
> +int kvmhv_emulate_priv(struct kvm_run *run, struct kvm_vcpu *vcpu,
> +			unsigned int instr)
> +{
> +	int rc = EMULATE_FAIL;
> +
> +	switch (get_op(instr)) {
> +	case 31:
> +		switch (get_xop(instr)) {
> +		case OP_31_XOP_MTSPR:
> +			rc = kvmhv_emulate_priv_mtspr(run, vcpu, instr);
> +			break;
> +		case OP_31_XOP_MFSPR:
> +			rc = kvmhv_emulate_priv_mfspr(run, vcpu, instr);
> +			break;
> +		default:
> +			rc = kvmhv_emulate_priv_op_31(run, vcpu, instr);
> +			break;
> +		}
> +
> +		if (rc == EMULATE_DONE)
> +			kvmppc_set_pc(vcpu, kvmppc_get_pc(vcpu) + 4);
> +		break;
> +	default:
> +		rc = kvmhv_emulate_priv_op(run, vcpu, instr);
> +		break;
> +	}
> +
> +	return rc;
> +}

-- 
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