lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 13 Jan 2022 22:09:33 +0000 From: Sean Christopherson <seanjc@...gle.com> To: Zeng Guang <guang.zeng@...el.com> Cc: Paolo Bonzini <pbonzini@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>, Tony Luck <tony.luck@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Kim Phillips <kim.phillips@....com>, Jarkko Sakkinen <jarkko@...nel.org>, Jethro Beekman <jethro@...tanix.com>, Kai Huang <kai.huang@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org, Robert Hu <robert.hu@...el.com>, Gao Chao <chao.gao@...el.com> Subject: Re: [PATCH v5 8/8] KVM: VMX: Resize PID-ponter table on demand for IPI virtualization On Fri, Dec 31, 2021, Zeng Guang wrote: > +static int vmx_expand_pid_table(struct kvm_vmx *kvm_vmx, int entry_idx) > +{ > + u64 *last_pid_table; > + int last_table_size, new_order; > + > + if (entry_idx <= kvm_vmx->pid_last_index) > + return 0; > + > + last_pid_table = kvm_vmx->pid_table; > + last_table_size = table_index_to_size(kvm_vmx->pid_last_index + 1); > + new_order = get_order(table_index_to_size(entry_idx + 1)); > + > + if (vmx_alloc_pid_table(kvm_vmx, new_order)) > + return -ENOMEM; > + > + memcpy(kvm_vmx->pid_table, last_pid_table, last_table_size); > + kvm_make_all_cpus_request(&kvm_vmx->kvm, KVM_REQ_PID_TABLE_UPDATE); > + > + /* Now old PID table can be freed safely as no vCPU is using it. */ > + free_pages((unsigned long)last_pid_table, get_order(last_table_size)); This is terrifying. I think it's safe? But it's still terrifying. Rather than dynamically react as vCPUs are created, what about we make max_vcpus common[*], extend KVM_CAP_MAX_VCPUS to allow userspace to override max_vcpus, and then have the IPIv support allocate the PID table on first vCPU creation instead of in vmx_vm_init()? That will give userspace an opportunity to lower max_vcpus to reduce memory consumption without needing to dynamically muck with the table in KVM. Then this entire patch goes away.
Powered by blists - more mailing lists