From: "H. Peter Anvin" <hpa@zytor.com> To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Tang Chen <tangchen@cn.fujitsu.com>, robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, akpm@linux-foundation.org, tj@kernel.org, trenn@suse.de, yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org, mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, zhangyanfei@cn.fujitsu.com, yanghy@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH 5/8] x86, brk: Make extend_brk() available with va/pa. Date: Wed, 21 Aug 2013 17:04:21 +0200 [thread overview] Message-ID: <025ad747-18b5-4d7a-8eea-9ba8a5b0d53c@email.android.com> (raw) In-Reply-To: <20130821144258.GH2593@phenom.dumpdata.com> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: >On Wed, Aug 21, 2013 at 02:35:36PM +0200, H. Peter Anvin wrote: >> Global symbols are inaccessible in physical mode. > >Even if they are embedded in the assembler code and use >GLOBAL(paging_enabled) ? Yes, because the address is different in physical mode. Think about it. You could do a *function* like: paging_enabled: mov (%esp),%edx xor %eax,%eax cmpl $PAGE_OFFSET,%edx setae %al ret >> >> This is incidentally yet another example of "PV/weird platform >violence", since in their absence it would be trivial to work around >this by using segmentation. > >I don't follow why it could not. > >Why can't there be a __pa_symbol(paging_enabled) that is used. Won't >that in effect allow you to check the contents of that 'global >constant' even when you don't have paging enabled? Yes. But not once paging has been turned on. >> >>As mentioned above, on 32bit before paging is enabled, we have to >> >>access variables >> >>with pa. So introduce a "bool is_phys" parameter to extend_brk(), >and >> >>convert va >> >>to pa is it is true. >> > >> >Could you do it differently? Meaning have a global symbol >> >(paging_enabled) which will be used by most of the functions you >> >changed in this patch and the next ones? It would naturally be >enabled >> >when paging is on and __va addresses can be used. >> > >> >That could also be used in the printk case to do a BUG_ON before >paging >> >is enabled on 32bit. Or perhaps use a different code path to deal >with >> >using __pa address. >> > >> >? -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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From: "H. Peter Anvin" <hpa@zytor.com> To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Tang Chen <tangchen@cn.fujitsu.com>, robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl, lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu, akpm@linux-foundation.org, tj@kernel.org, trenn@suse.de, yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org, mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, zhangyanfei@cn.fujitsu.com, yanghy@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH 5/8] x86, brk: Make extend_brk() available with va/pa. Date: Wed, 21 Aug 2013 17:04:21 +0200 [thread overview] Message-ID: <025ad747-18b5-4d7a-8eea-9ba8a5b0d53c@email.android.com> (raw) In-Reply-To: <20130821144258.GH2593@phenom.dumpdata.com> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: >On Wed, Aug 21, 2013 at 02:35:36PM +0200, H. Peter Anvin wrote: >> Global symbols are inaccessible in physical mode. > >Even if they are embedded in the assembler code and use >GLOBAL(paging_enabled) ? Yes, because the address is different in physical mode. Think about it. You could do a *function* like: paging_enabled: mov (%esp),%edx xor %eax,%eax cmpl $PAGE_OFFSET,%edx setae %al ret >> >> This is incidentally yet another example of "PV/weird platform >violence", since in their absence it would be trivial to work around >this by using segmentation. > >I don't follow why it could not. > >Why can't there be a __pa_symbol(paging_enabled) that is used. Won't >that in effect allow you to check the contents of that 'global >constant' even when you don't have paging enabled? Yes. But not once paging has been turned on. >> >>As mentioned above, on 32bit before paging is enabled, we have to >> >>access variables >> >>with pa. So introduce a "bool is_phys" parameter to extend_brk(), >and >> >>convert va >> >>to pa is it is true. >> > >> >Could you do it differently? Meaning have a global symbol >> >(paging_enabled) which will be used by most of the functions you >> >changed in this patch and the next ones? It would naturally be >enabled >> >when paging is on and __va addresses can be used. >> > >> >That could also be used in the printk case to do a BUG_ON before >paging >> >is enabled on 32bit. Or perhaps use a different code path to deal >with >> >using __pa address. >> > >> >? -- Sent from my mobile phone. Please excuse brevity and lack of formatting.
next prev parent reply other threads:[~2013-08-21 15:04 UTC|newest] Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-08-21 10:15 [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 1/8] x86: Make get_ramdisk_{image|size}() global Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 2/8] x86, microcode: Use get_ramdisk_{image|size}() in microcode handling Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 3/8] x86, acpi: Move table_sigs[] to stack Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 4/8] x86, acpi, brk: Extend BRK 256KB to store acpi override tables Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 5/8] x86, brk: Make extend_brk() available with va/pa Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 12:26 ` Konrad Rzeszutek Wilk 2013-08-21 12:26 ` Konrad Rzeszutek Wilk 2013-08-21 12:35 ` H. Peter Anvin 2013-08-21 12:35 ` H. Peter Anvin 2013-08-21 14:42 ` Konrad Rzeszutek Wilk 2013-08-21 14:42 ` Konrad Rzeszutek Wilk 2013-08-21 15:04 ` H. Peter Anvin [this message] 2013-08-21 15:04 ` H. Peter Anvin 2013-08-21 10:15 ` [PATCH 6/8] x86, acpi: Make acpi_initrd_override() available with va or pa Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 7/8] x86, acpi, brk: Make early_alloc_acpi_override_tables_buf() available with va/pa Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:15 ` [PATCH 8/8] x86, acpi: Do acpi_initrd_override() earlier in head_32.S/head64.c Tang Chen 2013-08-21 10:15 ` Tang Chen 2013-08-21 10:42 ` [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier Tang Chen 2013-08-21 10:42 ` Tang Chen 2013-08-21 13:06 ` Tejun Heo 2013-08-21 13:06 ` Tejun Heo 2013-08-21 15:00 ` Zhang Yanfei 2013-08-21 15:00 ` Zhang Yanfei 2013-08-21 15:36 ` Tejun Heo 2013-08-21 15:36 ` Tejun Heo 2013-08-21 19:31 ` Toshi Kani 2013-08-21 19:31 ` Toshi Kani 2013-08-21 19:54 ` Tejun Heo 2013-08-21 19:54 ` Tejun Heo 2013-08-21 20:29 ` Toshi Kani 2013-08-21 20:29 ` Toshi Kani 2013-08-21 20:40 ` Tejun Heo 2013-08-21 20:40 ` Tejun Heo 2013-08-21 22:36 ` Toshi Kani 2013-08-21 22:36 ` Toshi Kani 2013-08-22 3:32 ` Tejun Heo 2013-08-22 3:32 ` Tejun Heo 2013-08-22 15:52 ` Toshi Kani 2013-08-22 15:52 ` Toshi Kani 2013-08-22 18:31 ` Tejun Heo 2013-08-22 18:31 ` Tejun Heo 2013-08-22 19:39 ` Zhang Yanfei 2013-08-22 19:39 ` Zhang Yanfei 2013-08-22 19:45 ` Tejun Heo 2013-08-22 19:45 ` Tejun Heo 2013-08-22 20:11 ` Toshi Kani 2013-08-22 20:11 ` Toshi Kani 2013-08-22 20:21 ` Tejun Heo 2013-08-22 20:21 ` Tejun Heo 2013-08-22 20:35 ` Tejun Heo 2013-08-22 20:35 ` Tejun Heo 2013-08-22 21:06 ` Toshi Kani 2013-08-22 21:06 ` Toshi Kani 2013-08-22 21:21 ` Tejun Heo 2013-08-22 21:21 ` Tejun Heo 2013-08-22 22:17 ` Toshi Kani 2013-08-22 22:17 ` Toshi Kani 2013-08-23 13:04 ` Tejun Heo 2013-08-23 13:04 ` Tejun Heo 2013-08-23 13:08 ` H. Peter Anvin 2013-08-23 13:08 ` H. Peter Anvin 2013-08-23 14:19 ` Tejun Heo 2013-08-23 14:19 ` Tejun Heo 2013-08-23 14:24 ` H. Peter Anvin 2013-08-23 14:24 ` H. Peter Anvin 2013-08-23 14:24 ` H. Peter Anvin 2013-08-23 14:35 ` Tejun Heo 2013-08-23 14:35 ` Tejun Heo 2013-08-23 14:57 ` Tejun Heo 2013-08-23 14:57 ` Tejun Heo 2013-08-23 16:14 ` Toshi Kani 2013-08-23 16:14 ` Toshi Kani 2013-08-23 16:24 ` Tejun Heo 2013-08-23 16:24 ` Tejun Heo 2013-08-23 17:13 ` Toshi Kani 2013-08-23 17:13 ` Toshi Kani 2013-08-23 17:29 ` Zhang Yanfei 2013-08-23 17:29 ` Zhang Yanfei 2013-08-23 16:54 ` Zhang Yanfei 2013-08-23 16:54 ` Zhang Yanfei 2013-08-23 18:18 ` Yinghai Lu 2013-08-23 18:18 ` Yinghai Lu 2013-08-23 18:25 ` H. Peter Anvin 2013-08-23 20:08 ` Yinghai Lu 2013-08-23 20:30 ` Russ Anderson 2013-08-23 20:48 ` Yinghai Lu 2013-08-23 21:50 ` chen tang 2013-08-23 21:52 ` Moore, Robert 2013-08-23 22:05 ` Yinghai Lu 2013-08-23 22:08 ` Yinghai Lu 2013-08-23 22:40 ` chen tang 2013-08-23 23:04 ` Yinghai Lu 2013-08-24 2:41 ` Russ Anderson 2013-08-23 20:33 ` chen tang 2013-08-23 20:33 ` chen tang 2013-08-23 21:08 ` Yinghai Lu 2013-08-23 21:08 ` Yinghai Lu 2013-08-23 22:27 ` chen tang 2013-08-23 22:27 ` chen tang 2013-08-23 18:29 ` Toshi Kani 2013-08-23 18:29 ` Toshi Kani 2013-08-23 21:37 ` chen tang 2013-08-23 21:37 ` chen tang 2013-08-23 21:52 ` Tejun Heo 2013-08-23 21:52 ` Tejun Heo 2013-08-23 23:56 ` chen tang 2013-08-23 23:56 ` chen tang
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