Subject: Re: [PATCH v5 2/3] KVM: PPC: Book3S HV: Add support for H_RPT_INVALIDATE

From: David Gibson <[email-masked]>
Date: Thu, 4 Mar 2021 17:56:26 +1100

On Tue, Mar 02, 2021 at 10:28:53AM +0530, Bharata B Rao wrote:
> On Tue, Mar 02, 2021 at 12:45:18PM +1100, David Gibson wrote:
> > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> > > index 45fd862ac128..38ce3f21b21f 100644
> > > --- a/Documentation/virt/kvm/api.rst
> > > +++ b/Documentation/virt/kvm/api.rst
> > > @@ -6225,6 +6225,24 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them.
> > >  This capability can be used to check / enable 2nd DAWR feature provided
> > >  by POWER10 processor.
> > >  
> > > +7.23 KVM_CAP_PPC_RPT_INVALIDATE
> > > +------------------------------
> > > +
> > > +:Capability: KVM_CAP_PPC_RPT_INVALIDATE
> > > +:Architectures: ppc
> > > +:Type: vm
> > > +
> > > +This capability indicates that the kernel is capable of handling
> > > +H_RPT_INVALIDATE hcall.
> > > +
> > > +In order to enable the use of H_RPT_INVALIDATE in the guest,
> > > +user space might have to advertise it for the guest. For example,
> > > +IBM pSeries (sPAPR) guest starts using it if "hcall-rpt-invalidate" is
> > > +present in the "ibm,hypertas-functions" device-tree property.
> > > +
> > > +This capability is enabled for hypervisors on platforms like POWER9
> > > +that support radix MMU.
> > 
> > Does this mean that KVM will handle the hypercall, even if not
> > explicitly enabled by userspace (qemu)?  That's generally not what we
> > want, since we need to allow qemu to set up backwards compatible
> > guests.
> 
> This capability only indicates that hypervisor supports the hcall.
> 
> QEMU will check for this and conditionally enable the hcall
> (via KVM_CAP_PPC_ENABLE_HCALL ioctl). Enabling the hcall is
> conditional to cap-rpt-invalidate sPAPR machine capability being
> enabled by the user. Will post a followup QEMU patch shortly.

Ok.

> Older QEMU patch can be found here:
> https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg00627.html
> 
> > 
> > > +
> > >  8. Other capabilities.
> > >  ======================
> > >  
> > > diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h b/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
> > > index 8b33601cdb9d..a46fd37ad552 100644
> > > --- a/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
> > > +++ b/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
> > > @@ -4,6 +4,10 @@
> > >  
> > >  #include <asm/hvcall.h>
> > >  
> > > +#define RIC_FLUSH_TLB 0
> > > +#define RIC_FLUSH_PWC 1
> > > +#define RIC_FLUSH_ALL 2
> > > +
> > >  struct vm_area_struct;
> > >  struct mm_struct;
> > >  struct mmu_gather;
> > > diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> > > index 2f5f919f6cd3..a1515f94400e 100644
> > > --- a/arch/powerpc/include/asm/kvm_book3s.h
> > > +++ b/arch/powerpc/include/asm/kvm_book3s.h
> > > @@ -305,6 +305,9 @@ void kvmhv_set_ptbl_entry(unsigned int lpid, u64 dw0, u64 dw1);
> > >  void kvmhv_release_all_nested(struct kvm *kvm);
> > >  long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu);
> > >  long kvmhv_do_nested_tlbie(struct kvm_vcpu *vcpu);
> > > +long kvmhv_h_rpti_nested(struct kvm_vcpu *vcpu, unsigned long lpid,
> > > +			 unsigned long type, unsigned long pg_sizes,
> > > +			 unsigned long start, unsigned long end);
> > >  int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu,
> > >  			  u64 time_limit, unsigned long lpcr);
> > >  void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr);
> > > diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> > > index 652ce85f9410..820caf4e01b7 100644
> > > --- a/arch/powerpc/include/asm/mmu_context.h
> > > +++ b/arch/powerpc/include/asm/mmu_context.h
> > > @@ -124,8 +124,19 @@ static inline bool need_extra_context(struct mm_struct *mm, unsigned long ea)
> > >  
> > >  #if defined(CONFIG_KVM_BOOK3S_HV_POSSIBLE) && defined(CONFIG_PPC_RADIX_MMU)
> > >  extern void radix_kvm_prefetch_workaround(struct mm_struct *mm);
> > > +void do_h_rpt_invalidate(unsigned long pid, unsigned long lpid,
> > > +			 unsigned long type, unsigned long page_size,
> > > +			 unsigned long psize, unsigned long start,
> > > +			 unsigned long end);
> > >  #else
> > >  static inline void radix_kvm_prefetch_workaround(struct mm_struct *mm) { }
> > > +static inline void do_h_rpt_invalidate(unsigned long pid,
> > > +				       unsigned long lpid,
> > > +				       unsigned long type,
> > > +				       unsigned long page_size,
> > > +				       unsigned long psize,
> > > +				       unsigned long start,
> > > +				       unsigned long end) { }
> > >  #endif
> > >  
> > >  extern void switch_cop(struct mm_struct *next);
> > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> > > index 13bad6bf4c95..d83f006fc19d 100644
> > > --- a/arch/powerpc/kvm/book3s_hv.c
> > > +++ b/arch/powerpc/kvm/book3s_hv.c
> > > @@ -921,6 +921,69 @@ static int kvmppc_get_yield_count(struct kvm_vcpu *vcpu)
> > >  	return yield_count;
> > >  }
> > >  
> > > +static void do_h_rpt_invalidate_prs(unsigned long pid, unsigned long lpid,
> > > +				    unsigned long type, unsigned long pg_sizes,
> > > +				    unsigned long start, unsigned long end)
> > > +{
> > > +	unsigned long psize;
> > > +	struct mmu_psize_def *def;
> > > +
> > > +	for (psize = 0; psize < MMU_PAGE_COUNT; psize++) {
> > > +		def = &mmu_psize_defs[psize];
> > > +		if (pg_sizes & def->h_rpt_pgsize)
> > > +			do_h_rpt_invalidate(pid, lpid, type,
> > > +					    (1UL << def->shift), psize,
> > > +					    start, end);
> > > +	}
> > > +}
> > > +
> > > +static void kvmppc_nested_rpt_invalidate(struct kvm_vcpu *vcpu)
> > > +{
> > > +	do_h_rpt_invalidate_prs(kvmppc_get_gpr(vcpu, 4),
> > > +				vcpu->arch.nested->shadow_lpid,
> > > +				kvmppc_get_gpr(vcpu, 5),
> > > +				kvmppc_get_gpr(vcpu, 6),
> > > +				kvmppc_get_gpr(vcpu, 7),
> > > +				kvmppc_get_gpr(vcpu, 8));
> > > +	kvmppc_set_gpr(vcpu, 3, H_SUCCESS);
> > > +}
> > > +
> > > +static long kvmppc_h_rpt_invalidate(struct kvm_vcpu *vcpu,
> > > +				    unsigned long pid, unsigned long target,
> > > +				    unsigned long type, unsigned long pg_sizes,
> > > +				    unsigned long start, unsigned long end)
> > > +{
> > > +	if (!kvm_is_radix(vcpu->kvm))
> > > +		return H_UNSUPPORTED;
> > > +
> > > +	/*
> > > +	 * For nested guests, this hcall is handled in
> > > +	 * L0. See kvmppc_handle_nested_exit() for details.
> > > +	 */
> > > +	if (kvmhv_on_pseries())
> > > +		return H_UNSUPPORTED;
> > > +
> > > +	if (end < start)
> > > +		return H_P5;
> > > +
> > > +	if (type & H_RPTI_TYPE_NESTED) {
> > > +		if (!nesting_enabled(vcpu->kvm))
> > > +			return H_FUNCTION;
> > > +
> > > +		/* Support only cores as target */
> > > +		if (target != H_RPTI_TARGET_CMMU)
> > > +			return H_P2;
> > > +
> > 
> > IIUC, we'll hit this code path if an L1 calls this on behalf of an L2,
> 
> Correct.
> 
> > whereas we'll hit the nested exit code path going straight to
> > kvmhv_h_rpti_nested() if an L2 calls it on behalf of an L3.  Is that
> > right?
> 
> We will hit the nested exit code path when L2 calls it on behalf
> of L3. Looks like I am not handling this case (hcall issued by
> L2 on behalf of L3 for handling partition scoped translations)
> in the nested exit path.
> 
> > 
> > > +		return kvmhv_h_rpti_nested(vcpu, pid,
> > > +					   (type & ~H_RPTI_TYPE_NESTED),
> > > +					    pg_sizes, start, end);
> > > +	}
> > > +
> > > +	do_h_rpt_invalidate_prs(pid, vcpu->kvm->arch.lpid, type, pg_sizes,
> > > +				start, end);
> > > +	return H_SUCCESS;
> > > +}
> > > +
> > >  int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> > >  {
> > >  	unsigned long req = kvmppc_get_gpr(vcpu, 3);
> > > @@ -1129,6 +1192,14 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> > >  		 */
> > >  		ret = kvmppc_h_svm_init_abort(vcpu->kvm);
> > >  		break;
> > > +	case H_RPT_INVALIDATE:
> > > +		ret = kvmppc_h_rpt_invalidate(vcpu, kvmppc_get_gpr(vcpu, 4),
> > > +					      kvmppc_get_gpr(vcpu, 5),
> > > +					      kvmppc_get_gpr(vcpu, 6),
> > > +					      kvmppc_get_gpr(vcpu, 7),
> > > +					      kvmppc_get_gpr(vcpu, 8),
> > > +					      kvmppc_get_gpr(vcpu, 9));
> > > +		break;
> > >  
> > >  	default:
> > >  		return RESUME_HOST;
> > > @@ -1175,6 +1246,7 @@ static int kvmppc_hcall_impl_hv(unsigned long cmd)
> > >  	case H_XIRR_X:
> > >  #endif
> > >  	case H_PAGE_INIT:
> > > +	case H_RPT_INVALIDATE:
> > >  		return 1;
> > >  	}
> > >  
> > > @@ -1590,6 +1662,24 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
> > >  		if (!xics_on_xive())
> > >  			kvmppc_xics_rm_complete(vcpu, 0);
> > >  		break;
> > > +	case BOOK3S_INTERRUPT_SYSCALL:
> > > +	{
> > > +		unsigned long req = kvmppc_get_gpr(vcpu, 3);
> > > +
> > > +		/*
> > > +		 * The H_RPT_INVALIDATE hcalls issued by nested
> > > +		 * guests for process scoped invalidations when
> > > +		 * GTSE=0, are handled here in L0.
> > > +		 */
> > 
> > What if the L2 is not calling this for the GTSE=0 case, but on behalf
> > of an L3?
> 
> That case would be for flushing partition scoped translations. I am
> realizing that I am not handling that case, but it should be handled
> here in the nested hcall exit path.
> 
> Currently I am handling only the hcall requests for process scoped
> translations from nested guests here.

Ok.  At the very least you need to detect and fail for that case.

> > 
> > > +		if (req == H_RPT_INVALIDATE) {
> > > +			kvmppc_nested_rpt_invalidate(vcpu);
> > > +			r = RESUME_GUEST;
> > > +			break;
> > > +		}
> > > +
> > > +		r = RESUME_HOST;
> > > +		break;
> > > +	}
> > >  	default:
> > >  		r = RESUME_HOST;
> > >  		break;
> > > diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> > > index 0cd0e7aad588..ca43b2d38dce 100644
> > > --- a/arch/powerpc/kvm/book3s_hv_nested.c
> > > +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> > > @@ -1191,6 +1191,83 @@ long kvmhv_do_nested_tlbie(struct kvm_vcpu *vcpu)
> > >  	return H_SUCCESS;
> > >  }
> > >  
> > > +static long do_tlb_invalidate_nested_tlb(struct kvm_vcpu *vcpu,
> > > +					 unsigned long lpid,
> > > +					 unsigned long page_size,
> > > +					 unsigned long ap,
> > > +					 unsigned long start,
> > > +					 unsigned long end)
> > > +{
> > > +	unsigned long addr = start;
> > > +	int ret;
> > > +
> > > +	do {
> > > +		ret = kvmhv_emulate_tlbie_tlb_addr(vcpu, lpid, ap,
> > > +						   get_epn(addr));
> > > +		if (ret)
> > > +			return ret;
> > > +		addr += page_size;
> > > +	} while (addr < end);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > > +static long do_tlb_invalidate_nested_all(struct kvm_vcpu *vcpu,
> > > +					 unsigned long lpid)
> > > +{
> > > +	struct kvm *kvm = vcpu->kvm;
> > > +	struct kvm_nested_guest *gp;
> > > +
> > > +	gp = kvmhv_get_nested(kvm, lpid, false);
> > > +	if (gp) {
> > > +		kvmhv_emulate_tlbie_lpid(vcpu, gp, RIC_FLUSH_ALL);
> > > +		kvmhv_put_nested(gp);
> > > +	}
> > > +	return H_SUCCESS;
> > > +}
> > > +
> > > +long kvmhv_h_rpti_nested(struct kvm_vcpu *vcpu, unsigned long lpid,
> > > +			 unsigned long type, unsigned long pg_sizes,
> > > +			 unsigned long start, unsigned long end)
> > > +{
> > > +	struct kvm_nested_guest *gp;
> > > +	long ret;
> > > +	unsigned long psize, ap;
> > > +
> > > +	/*
> > > +	 * If L2 lpid isn't valid, we need to return H_PARAMETER.
> > > +	 *
> > > +	 * However, nested KVM issues a L2 lpid flush call when creating
> > > +	 * partition table entries for L2. This happens even before the
> > > +	 * corresponding shadow lpid is created in HV which happens in
> > > +	 * H_ENTER_NESTED call. Since we can't differentiate this case from
> > > +	 * the invalid case, we ignore such flush requests and return success.
> > > +	 */
> > 
> > What if this is being called on behalf of an L3 or deeper?  Do we need
> > something to do a translation from L3 to L2 addresses?
> 
> I am not sure, I will have to check if gp->shadow_lpid points to
> correct nested LPID in all the cases.
> 
> > 
> > > +	gp = kvmhv_find_nested(vcpu->kvm, lpid);
> > > +	if (!gp)
> > > +		return H_SUCCESS;
> 
> Regards,
> Bharata.
> 

-- 
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