From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Ellerman Date: Tue, 15 Aug 2023 10:45:14 +0000 Subject: Re: [PATCH v3 4/6] KVM: PPC: Book3s HV: Hold LPIDs in an unsigned long Message-Id: <87ttt0d1ol.fsf@mail.lhotse> List-Id: References: <20230807014553.1168699-1-jniethe5@gmail.com> <20230807014553.1168699-5-jniethe5@gmail.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Nicholas Piggin , Jordan Niethe , linuxppc-dev@lists.ozlabs.org Cc: mikey@neuling.org, kvm@vger.kernel.org, sbhat@linux.ibm.com, amachhiw@linux.vnet.ibm.com, gautam@linux.ibm.com, kvm-ppc@vger.kernel.org, kconsul@linux.vnet.ibm.com, vaibhav@linux.ibm.com "Nicholas Piggin" writes: > On Mon Aug 7, 2023 at 11:45 AM AEST, Jordan Niethe wrote: >> The LPID register is 32 bits long. The host keeps the lpids for each >> guest in an unsigned word struct kvm_arch. Currently, LPIDs are already >> limited by mmu_lpid_bits and KVM_MAX_NESTED_GUESTS_SHIFT. >> >> The nestedv2 API returns a 64 bit "Guest ID" to be used be the L1 host >> for each L2 guest. This value is used as an lpid, e.g. it is the >> parameter used by H_RPT_INVALIDATE. To minimize needless special casing >> it makes sense to keep this "Guest ID" in struct kvm_arch::lpid. >> >> This means that struct kvm_arch::lpid is too small so prepare for this >> and make it an unsigned long. This is not a problem for the KVM-HV and >> nestedv1 cases as their lpid values are already limited to valid ranges >> so in those contexts the lpid can be used as an unsigned word safely as >> needed. >> >> In the PAPR, the H_RPT_INVALIDATE pid/lpid parameter is already >> specified as an unsigned long so change pseries_rpt_invalidate() to >> match that. Update the callers of pseries_rpt_invalidate() to also take >> an unsigned long if they take an lpid value. > > I don't suppose it would be worth having an lpid_t. > >> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c >> index 4adff4f1896d..229f0a1ffdd4 100644 >> --- a/arch/powerpc/kvm/book3s_xive.c >> +++ b/arch/powerpc/kvm/book3s_xive.c >> @@ -886,10 +886,10 @@ int kvmppc_xive_attach_escalation(struct kvm_vcpu *vcpu, u8 prio, >> >> if (single_escalation) >> name = kasprintf(GFP_KERNEL, "kvm-%d-%d", >> - vcpu->kvm->arch.lpid, xc->server_num); >> + (unsigned int)vcpu->kvm->arch.lpid, xc->server_num); >> else >> name = kasprintf(GFP_KERNEL, "kvm-%d-%d-%d", >> - vcpu->kvm->arch.lpid, xc->server_num, prio); >> + (unsigned int)vcpu->kvm->arch.lpid, xc->server_num, prio); >> if (!name) { >> pr_err("Failed to allocate escalation irq name for queue %d of VCPU %d\n", >> prio, xc->server_num); > > I would have thought you'd keep the type and change the format. Yeah. Don't we risk having ambigious names by discarding the high bits? Not sure that would be a bug per se, but it could be confusing. cheers