linux-kernel - Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles

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

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20070312162405.GA21463@amd.com>
Date:	Mon, 12 Mar 2007 17:24:05 +0100
From:	"Joerg Roedel" <joerg.roedel@....com>
To:	"Avi Kivity" <avi@...o.co.il>
cc:	discuss@...-64.org, "Andi Kleen" <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync()

On Mon, Mar 12, 2007 at 06:08:11PM +0200, Avi Kivity wrote:
> Joerg Roedel wrote:
> >On Fri, Mar 09, 2007 at 08:10:03PM +0200, Avi Kivity wrote:
> >  
> >>Joerg Roedel wrote:
> >>    
> >>>From: Joerg Roedel <joerg.roedel@....com>
> >>>
> >>>This patch simplifies the get_cycles_sync() function by removing
> >>>the #ifdefs from it. Further it introduces an optimization for AMD
> >>>processors. There the RDTSCP instruction is used instead of CPUID;RDTSC
> >>>which is helpfull if the kernel runs as a KVM guest. Running as a guest
> >>>makes CPUID very expensive because it causes an intercept of the guest.
> >>>
> >>> +#define RDTSCP ".byte 0x0f, 0x01, 0xf9"
> >>>+	alternative_io_two("cpuid\nrdtsc",
> >>>+			   "rdtsc", X86_FEATURE_SYNC_RDTSC,
> >>>+			   ".byte 0x0f, 0x01, 0xf9", X86_FEATURE_RDTSCP,
> >>>       
> >>why not use the RDTSCP macro here?
> >>    
> >
> >Does this macro exist? I couldn't found it in the current git tree. And
> >the rdtscp macros in msr.h use the plain opcode too.
> >  
> 
> -ENOCOFFEE?  You defined the macro 3 lines above the .byte directive...

Yes, lack of coffee, and even worse -EBLINDHACKER :-(

-- 
Joerg Roedel
Operating System Research Center
AMD Saxony LLC & Co. KG


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/