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Date: Thu, 09 Mar 2017 14:25:58 +0100 From: Daniel Borkmann <daniel@...earbox.net> To: Thomas Gleixner <tglx@...utronix.de> CC: Kees Cook <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org>, Peter Anvin <hpa@...or.com>, Fengguang Wu <fengguang.wu@...el.com>, Network Development <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>, ast@...com, the arch/x86 maintainers <x86@...nel.org>, "David S. Miller" <davem@...emloft.net> Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request at 0000a7cf On 03/09/2017 02:10 PM, Thomas Gleixner wrote: > On Thu, 9 Mar 2017, Daniel Borkmann wrote: >> With regard to CPA_FLUSHTLB that Linus mentioned, when I investigated >> code paths in change_page_attr_set_clr(), I did see that CPA_FLUSHTLB >> was set each time we switched attrs and a cpa_flush_range() was >> performed (with the correct number of pages and cache set to 0). That >> would be a __flush_tlb_all() eventually. >> >> Hmm, it indeed might seem likely that this could be an emulation bug. > > Which variant of __flush_tlb_all() is used when the test fails? > > Check for the following flags in /proc/cpuinfo: pge invpcid I added the following and booted with both variants: printk("X86_FEATURE_PGE:%u\n", static_cpu_has(X86_FEATURE_PGE)); printk("X86_FEATURE_INVPCID:%u\n", static_cpu_has(X86_FEATURE_INVPCID)); "-cpu host" gives: [ 8.326117] X86_FEATURE_PGE:1 [ 8.326381] X86_FEATURE_INVPCID:1 "-cpu kvm64" gives: [ 8.517069] X86_FEATURE_PGE:1 [ 8.517393] X86_FEATURE_INVPCID:0 Thanks, Daniel
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