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Message-ID: <20130428005814.GB10354@somewhere> Date: Sun, 28 Apr 2013 02:58:16 +0200 From: Frederic Weisbecker <fweisbec@...il.com> To: Oleg Nesterov <oleg@...hat.com> Cc: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Cyrill Gorcunov <gorcunov@...il.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Thomas Gleixner <tglx@...utronix.de>, David Miller <davem@...emloft.net>, Theodore Ts'o <tytso@....edu>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, the arch/x86 maintainers <x86@...nel.org>, Network Development <netdev@...r.kernel.org>, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org> Subject: Re: [PATCH v2] x86: make DR*_RESERVED unsigned long On Sat, Apr 27, 2013 at 04:45:37PM +0200, Oleg Nesterov wrote: > On 04/26, Oleg Nesterov wrote: > > > On 04/26, H. Peter Anvin wrote: > > > > > > On 04/26/2013 09:38 AM, Oleg Nesterov wrote: > > > > > > > > - do_debug: > > > > > > > > dr6 &= ~DR6_RESERVED; > > > > > > > > this also wrongly clears 32-63 bits. Fortunately these > > > > bits are reserved and must be zero. > > > > > > I don't think this is wrongly at all. > > > > OK, I meant that it also clears the bits that are not specified in > > DR6_RESERVED mask. > > > > > The whole point is to mask out > > > the bits that the handler doesn't want to deal with, so masking out the > > > reserved bits [63:32] seems reasonable to me. > > > > Then we should do > > > > - #define DR6_RESERVED 0xFFFF0FF0 > > + #define DR6_RESERVED 0xFFFFFFFFFFFF0FF0 > > > > ? > > > > or what? (just in case, I will happily agree with "do nothing" ;) > > Or we can do the s/reserved/mask/ change and avoid any "unexpected" > effect of "long &= ~int". This allso allows to kill ifdef(__i386__). > > But this is include/uapi, I do not know if I can simply remove the > old define's. > > In short: whatever you prefer, including "leave it alone". > > Oleg. > > diff --git a/arch/x86/include/uapi/asm/debugreg.h b/arch/x86/include/uapi/asm/debugreg.h > index 3c0874d..2678b23 100644 > --- a/arch/x86/include/uapi/asm/debugreg.h > +++ b/arch/x86/include/uapi/asm/debugreg.h > @@ -14,8 +14,7 @@ > which debugging register was responsible for the trap. The other bits > are either reserved or not of interest to us. */ > > -/* Define reserved bits in DR6 which are always set to 1 */ > -#define DR6_RESERVED (0xFFFF0FF0) > +#define DR6_MASK (0xF00FU) /* Everything else is reserved */ I'm personally fine either with that or with Peter's suggestion to do: -#define DR6_RESERVED (0xFFFF0FF0) +#define DR6_RESERVED (~0xF00FUL) If this should stay stable UAPI, we probably want Peter's solution. Otherwise I really don't mind. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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