From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from tyo201.gate.nec.co.jp ([210.143.35.51]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1c1qIp-0006ex-TA for kexec@lists.infradead.org; Wed, 02 Nov 2016 07:49:45 +0000 From: Atsushi Kumagai Subject: RE: [PATCH Makedumpfile 1/4] x86_64: Calculate page_offset from pt_load Date: Wed, 2 Nov 2016 07:40:27 +0000 Message-ID: <0910DD04CBD6DE4193FCF86B9C00BE9701E7C84F@BPXM01GP.gisp.nec.co.jp> References: <4b2497eff40bd47eef59cdd6af165e700cfd4408.1477327674.git.panand@redhat.com> In-Reply-To: Content-Language: ja-JP MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Pratyush Anand , "bhe@redhat.com" Cc: "kexec@lists.infradead.org" , "dyoung@redhat.com" Hello Pratyush, >On Monday 24 October 2016 10:18 PM, Pratyush Anand wrote: >> page_offset can always be calculated as 'virtual - physical' for a direct >> mapping area on x86. Therefore, remove the version dependent calculation >> and use this method. >> >> Signed-off-by: Pratyush Anand >> --- >> arch/x86_64.c | 24 ++++++++++++++++++++---- >> 1 file changed, 20 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86_64.c b/arch/x86_64.c >> index ddf7be6bc57b..a96fd8ae00a1 100644 >> --- a/arch/x86_64.c >> +++ b/arch/x86_64.c >> @@ -44,6 +44,24 @@ get_xen_p2m_mfn(void) >> return NOT_FOUND_LONG_VALUE; >> } >> >> +static int >> +get_page_offset_x86_64(void) >> +{ >> + int i; >> + unsigned long long phys_start; >> + unsigned long long virt_start; >> + >> + for (i = 0; get_pt_load(i, &phys_start, NULL, &virt_start, NULL); i++) { >> + if (virt_start >= __START_KERNEL_map) { > >OK..So, this is the problem. We should have > >if (virt_start < __START_KERNEL_map) { > >Kernel text region lies above __START_KERNEL_map, which is linearly >mapped however not a direct mapping. Direct mapping region lies below it >instead. So, page_offset can only be calculated with a region which is >below __START_KERNEL_map. > >Thanks Baoquan for finding it. Could you explain the issue in more detail, what is the difference between "linear map" and "direct map" ? BTW, I confirmed that the difference of v2 patch is only this and the result of benchmark looks great, thank you very much. Regards, Atsushi Kumagai >> + info->page_offset = virt_start - phys_start; >> + return TRUE; >> + } >> + } >> + >> + ERRMSG("Can't get any pt_load to calculate page offset.\n"); >> + return FALSE; >> +} >> + >> int >> get_phys_base_x86_64(void) >> { >> @@ -159,10 +177,8 @@ get_versiondep_info_x86_64(void) >> else >> info->max_physmem_bits = _MAX_PHYSMEM_BITS_2_6_31; >> >> - if (info->kernel_version < KERNEL_VERSION(2, 6, 27)) >> - info->page_offset = __PAGE_OFFSET_ORIG; >> - else >> - info->page_offset = __PAGE_OFFSET_2_6_27; >> + if (!get_page_offset_x86_64()) >> + return FALSE; >> >> if (info->kernel_version < KERNEL_VERSION(2, 6, 31)) { >> info->vmalloc_start = VMALLOC_START_ORIG; >> > >_______________________________________________ >kexec mailing list >kexec@lists.infradead.org >http://lists.infradead.org/mailman/listinfo/kexec _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec