From: Daniel Borkmann <daniel@iogearbox.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>,
Laura Abbott <labbott@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>, Peter Anvin <hpa@zytor.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Network Development <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>, LKP <lkp@01.org>,
ast@fb.com, the arch/x86 maintainers <x86@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request at 0000a7cf
Date: Thu, 09 Mar 2017 15:53:30 +0100 [thread overview]
Message-ID: <58C16C6A.2060400@iogearbox.net> (raw)
In-Reply-To: <58C157E6.1010909@iogearbox.net>
On 03/09/2017 02:25 PM, Daniel Borkmann wrote:
> 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
Fwiw, I tried switching from using cr4 (__native_flush_tlb_global_irq_disabled())
to slower cr3 (__native_flush_tlb()) in "-cpu kvm64" mode, and it looks like it
also lets all test cases pass (rodata_test, test_setmem, test_bpf), no corruption
happening, etc.
Test diff used:
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 6fa8594..34f4582 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -188,9 +188,9 @@ static inline void __native_flush_tlb_single(unsigned long addr)
static inline void __flush_tlb_all(void)
{
- if (static_cpu_has(X86_FEATURE_PGE))
- __flush_tlb_global();
- else
+// if (static_cpu_has(X86_FEATURE_PGE))
+// __flush_tlb_global();
+// else
__flush_tlb();
}
next prev parent reply other threads:[~2017-03-09 14:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-01 12:54 [net/bpf] 3051bf36c2 BUG: unable to handle kernel paging request at 0000a7cf Fengguang Wu
2017-03-02 20:23 ` Fengguang Wu
2017-03-02 20:40 ` Daniel Borkmann
2017-03-08 19:25 ` Linus Torvalds
2017-03-08 22:27 ` Daniel Borkmann
2017-03-08 22:36 ` Kees Cook
2017-03-08 22:51 ` Daniel Borkmann
2017-03-08 23:55 ` Laura Abbott
2017-03-09 5:36 ` Kees Cook
2017-03-09 13:04 ` Daniel Borkmann
2017-03-09 13:10 ` Thomas Gleixner
2017-03-09 13:25 ` Daniel Borkmann
2017-03-09 14:49 ` Thomas Gleixner
2017-03-09 17:51 ` Daniel Borkmann
2017-03-09 18:08 ` David Miller
2017-03-09 18:10 ` Linus Torvalds
2017-03-09 18:15 ` Linus Torvalds
2017-03-09 18:31 ` Daniel Borkmann
2017-03-09 21:32 ` Daniel Borkmann
2017-03-09 21:55 ` Borislav Petkov
2017-03-09 22:07 ` Borislav Petkov
2017-03-09 22:11 ` Daniel Borkmann
2017-03-09 22:48 ` Borislav Petkov
2017-03-09 23:26 ` Linus Torvalds
2017-03-09 23:44 ` Borislav Petkov
2017-03-10 0:13 ` Daniel Borkmann
2017-03-12 21:40 ` Borislav Petkov
2017-03-09 14:53 ` Daniel Borkmann [this message]
2017-03-09 17:48 ` Linus Torvalds
2017-03-08 22:43 ` Linus Torvalds
2017-03-09 1:34 ` Fengguang Wu
2017-03-09 13:09 ` Thomas Gleixner
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