From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Gibson Subject: Re: [PATCH v3 22/33] KVM: PPC: Book3S HV: Handle page fault for a nested guest Date: Fri, 5 Oct 2018 12:46:12 +1000 Message-ID: <20181005024611.GA13763@umbus.fritz.box> References: <1538479892-14835-1-git-send-email-paulus@ozlabs.org> <1538479892-14835-23-git-send-email-paulus@ozlabs.org> <20181003053913.GP1886@umbus.fritz.box> <20181004092120.GA3255@fergus> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="u3/rZRmxL6MmkK24" Cc: linuxppc-dev@ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org To: Paul Mackerras Return-path: Content-Disposition: inline In-Reply-To: <20181004092120.GA3255@fergus> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane.org@lists.ozlabs.org Sender: "Linuxppc-dev" List-Id: kvm.vger.kernel.org --u3/rZRmxL6MmkK24 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Oct 04, 2018 at 07:21:20PM +1000, Paul Mackerras wrote: > On Wed, Oct 03, 2018 at 03:39:13PM +1000, David Gibson wrote: > > On Tue, Oct 02, 2018 at 09:31:21PM +1000, Paul Mackerras wrote: > > > From: Suraj Jitindar Singh > > > @@ -367,7 +367,9 @@ struct kvmppc_pte { > > > bool may_write : 1; > > > bool may_execute : 1; > > > unsigned long wimg; > > > + unsigned long rc; > > > u8 page_size; /* MMU_PAGE_xxx */ > > > + u16 page_shift; > >=20 > > It's a bit ugly that this has both page_size and page_shift, which is > > redundant information AFAICT. Also, why does page_shift need to be > > u16 - given that 2^255 bytes is much more than our supported address > > space, let alone a plausible page size. >=20 > These values are all essentially function outputs, so I don't think > it's ugly to have the same information in different forms. I actually > don't like using the MMU_PAGE_xxx values, because the information in > the mmu_psize_defs[] array depends on the MMU mode of the host, but > KVM needs to be able to work with guests in both MMU modes. More > generally I don't think it's a good idea that the KVM <-> guest > interface depends so much on what the host firmware tells us about the > physical machine we're on. Thus I'm trying to move away from using > MMU_PSIZE_xxx values and mmu_psize_defs[] in KVM code. Fair enough. > I'll change the type to u8. >=20 > > > diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kv= m/book3s_64_mmu_radix.c > > > index bd06a95..ee6f493 100644 > > > --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c > > > +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c > > > @@ -29,43 +29,16 @@ > > > */ > > > static int p9_supported_radix_bits[4] =3D { 5, 9, 9, 13 }; > > > =20 > > > -/* > > > - * Used to walk a partition or process table radix tree in guest mem= ory > > > - * Note: We exploit the fact that a partition table and a process > > > - * table have the same layout, a partition-scoped page table and a > > > - * process-scoped page table have the same layout, and the 2nd > > > - * doubleword of a partition table entry has the same layout as > > > - * the PTCR register. > > > - */ > > > -int kvmppc_mmu_radix_translate_table(struct kvm_vcpu *vcpu, gva_t ea= ddr, > > > - struct kvmppc_pte *gpte, u64 table, > > > - int table_index, u64 *pte_ret_p) > > > +int kvmppc_mmu_walk_radix_tree(struct kvm_vcpu *vcpu, gva_t eaddr, > > > + struct kvmppc_pte *gpte, u64 root, > > > + u64 *pte_ret_p) > > > { > > > struct kvm *kvm =3D vcpu->kvm; > > > int ret, level, ps; > > > - unsigned long ptbl, root; > > > - unsigned long rts, bits, offset; > > > - unsigned long size, index; > > > - struct prtb_entry entry; > > > + unsigned long rts, bits, offset, index; > > > u64 pte, base, gpa; > > > __be64 rpte; > > > =20 > > > - if ((table & PRTS_MASK) > 24) > > > - return -EINVAL; > > > - size =3D 1ul << ((table & PRTS_MASK) + 12); > > > - > > > - /* Is the table big enough to contain this entry? */ > > > - if ((table_index * sizeof(entry)) >=3D size) > > > - return -EINVAL; > > > - > > > - /* Read the table to find the root of the radix tree */ > > > - ptbl =3D (table & PRTB_MASK) + (table_index * sizeof(entry)); > > > - ret =3D kvm_read_guest(kvm, ptbl, &entry, sizeof(entry)); > > > - if (ret) > > > - return ret; > > > - > > > - /* Root is stored in the first double word */ > > > - root =3D be64_to_cpu(entry.prtb0); > >=20 > > This refactoring somewhat obscures the changes directly relevant to > > the nested guest handling. Ideally it would be nice to fold some of > > this into the earlier reworkings. >=20 > True, but given the rapidly approaching merge window, I'm not inclined > to rework it. Yeah, ok. >=20 > > > + if (ret) { > > > + /* We didn't find a pte */ > > > + if (ret =3D=3D -EINVAL) { > > > + /* Unsupported mmu config */ > > > + flags |=3D DSISR_UNSUPP_MMU; > > > + } else if (ret =3D=3D -ENOENT) { > > > + /* No translation found */ > > > + flags |=3D DSISR_NOHPTE; > > > + } else if (ret =3D=3D -EFAULT) { > > > + /* Couldn't access L1 real address */ > > > + flags |=3D DSISR_PRTABLE_FAULT; > > > + vcpu->arch.fault_gpa =3D fault_addr; > > > + } else { > > > + /* Unknown error */ > > > + return ret; > > > + } > > > + goto resume_host; > >=20 > > This is effectively forwarding the fault to L1, yes? In which case a > > different name might be better than the ambiguous "resume_host". >=20 > I'll change it to "forward_to_l1". Thanks. >=20 > Paul. >=20 >=20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. 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