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Date: Wed, 1 Nov 2017 17:56:45 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Prarit Bhargava <prarit@...hat.com> cc: linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...el.com>, Piotr Luc <piotr.luc@...el.com>, Kan Liang <kan.liang@...el.com>, Borislav Petkov <bp@...e.de>, Stephane Eranian <eranian@...gle.com>, Arvind Yadav <arvind.yadav.cs@...il.com>, Andy Lutomirski <luto@...nel.org>, Christian Borntraeger <borntraeger@...ibm.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Tom Lendacky <thomas.lendacky@....com>, Mathias Krause <minipli@...glemail.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Vitaly Kuznetsov <vkuznets@...hat.com> Subject: Re: [PATCH 2/3 v4] x86/topology: Avoid wasting 128k for package id array On Wed, 25 Oct 2017, Prarit Bhargava wrote: > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > index b390ff76e58f..f4ab1edf4e24 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -124,8 +124,10 @@ struct cpuinfo_x86 { > u16 booted_cores; > /* Physical processor id: */ > u16 phys_proc_id; > - /* Logical processor id: */ > + /* Logical processor (package) id: */ > u16 logical_proc_id; > + /* Physical package ID */ > + u16 phys_pkg_id; How is this new field used aside of being written to and how is it different from phys_proc_id? AFAICT, it's the same as all callers to topology_update_package_map() are handing in cpu_data->phys_proc_id. > +/** > + * topology_phys_to_logical_pkg - Map a physical package id to a logical > + * > + * Returns logical package id or -1 if not found > + */ > +int topology_phys_to_logical_pkg(unsigned int phys_pkg) > +{ > + int log_pkg; > + > + for (log_pkg = 0; log_pkg < logical_packages; log_pkg++) > + if (logical_to_physical_pkg_map[log_pkg] == phys_pkg) > + return log_pkg; > + > + return -1; > +} > +EXPORT_SYMBOL(topology_phys_to_logical_pkg); .... > + > + /* Allocate and copy a new array */ > + ltp_pkg_map_new = kmalloc(logical_packages * sizeof(u16), GFP_KERNEL); > + BUG_ON(!ltp_pkg_map_new); > + if (logical_to_physical_pkg_map) { > + memcpy(ltp_pkg_map_new, logical_to_physical_pkg_map, > + logical_packages * sizeof(u16)); > + kfree(logical_to_physical_pkg_map); > } > - physical_to_logical_pkg[pkg] = new; > + logical_to_physical_pkg_map = ltp_pkg_map_new; This lacks serialization and is therefore broken against a concurrent topology_phys_to_logical_pkg() call for obvious reasons. The current user is probably safe, but this really needs to be fixed now. Thanks, tglx
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