From: "H. Peter Anvin" <hpa@linux.intel.com>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v3] eal_common_cpuflags: Fix %rbx corruption, and simplify the code
Date: Mon, 24 Mar 2014 13:47:55 -0700 [thread overview]
Message-ID: <533099FB.5030702@linux.intel.com> (raw)
In-Reply-To: <20140324195206.GG19368@hmsreliant.think-freely.org>
On 03/24/2014 12:52 PM, Neil Horman wrote:
>>
> To add an extra sanity check in rte_get_flag_enabled. If we were moving to the
> use of C99 initalizers, I wanted something to catch the possibility that we skip
> a flag by accident (i.e. leave a zero initalized hole in the array). Except 0
> from my read is a valid value for all the fields of the array. So I bumped up
> the cpuid register enum by one and wrapped it in a macro. That way we can test
> for !feat->reg as an indicator that we're requesting feature support for a flag
> thats not listed in the array.
It actually isn't: there aren't any flags in CPUID leaf 0, so since the
code only looks for bits it'd be perfectly okay to reject leaf 0.
Another thing that I noted is that the code doesn't actually check that
any particular leaf is valid (by checking the maximum leaf number in
CPUID leaf 0xXXXX0000:EAX). Especially for the leaf 7 features this
could result in false positives, which obviously would be disastrous.
-hpa
next prev parent reply other threads:[~2014-03-24 20:46 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1395330830-1310-1-git-send-email-hpa@linux.intel.com>
2014-03-20 16:39 ` [dpdk-dev] [RFC UNTESTED PATCH] " Neil Horman
2014-03-20 17:02 ` Thomas Monjalon
2014-03-20 18:04 ` Neil Horman
2014-03-21 14:49 ` [dpdk-dev] [PATCH v2] " Neil Horman
2014-03-21 15:03 ` H. Peter Anvin
2014-03-21 17:48 ` Neil Horman
2014-03-24 11:18 ` Thomas Monjalon
2014-03-24 17:44 ` [dpdk-dev] [PATCH v3] " Neil Horman
2014-03-24 18:09 ` H. Peter Anvin
2014-03-24 19:52 ` Neil Horman
2014-03-24 20:47 ` H. Peter Anvin [this message]
2014-03-25 10:41 ` Neil Horman
2014-03-25 17:03 ` [dpdk-dev] [PATCH v4] " Neil Horman
2014-03-25 17:06 ` Chris Wright
2014-03-25 17:37 ` H. Peter Anvin
2014-03-25 19:52 ` [dpdk-dev] [PATCH v5] " Neil Horman
2014-03-25 20:51 ` H. Peter Anvin
2014-04-02 11:16 ` Neil Horman
2014-04-02 11:53 ` Thomas Monjalon
2014-04-02 12:42 ` Thomas Monjalon
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