Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Joerg Roedel <joro@8bytes.org>, Jiri Olsa <jolsa@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>
Subject: Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines
Date: Fri, 11 May 2018 11:45:26 -0300	[thread overview]
Message-ID: <20180511144526.GQ13491@kernel.org> (raw)
In-Reply-To: <291c0615-2b5c-0076-faeb-720df9ab5c84@intel.com>

Em Fri, May 11, 2018 at 02:18:01PM +0300, Adrian Hunter escreveu:
> On 10/05/18 23:47, Arnaldo Carvalho de Melo wrote:
> > Em Thu, May 10, 2018 at 05:19:22PM -0300, Arnaldo Carvalho de Melo escreveu:
> >> Em Thu, May 10, 2018 at 05:15:42PM -0300, Arnaldo Carvalho de Melo escreveu:
> >>> Em Thu, May 10, 2018 at 07:08:37PM +0000, Hunter, Adrian escreveu:
> >>>> Let me know if you want me to post the workaround patches separately,
> >>>> otherwise I will wait a bit before sending the patches again.
> > 
> >>> I'll see if I went thru all of the patches already...
> >  
> >> So I looked at the patches posted and one comment is about the terse
> >> commit logs for some of the kcore_copy patches, for instance:
> >  
> >> --------------------
> >>  In preparation to add more program headers, get rid of kernel_map and
> >> modules_map.
> >> --------------------
> >  
> >> Can't this be made a bit more verbose? Lemme re-read the patch...
> > 
> > So you had just one pointers to the kernel map and a module_maps, and
> > then this is replaced by kcore_copy__map() that instead of populating
> > those fields that are being removed:
> > 
> > -       struct phdr_data kernel_map;
> > -       struct phdr_data modules_map;
> > 
> > Will allocate and add "struct phdr_data" instances to the
> > kcore_copy_info->phdrs list, so I propose, to follow convention used
> > elsewhere in tools/perf/ that you rename kcore_copy__map() to
> > 
> >   kcore_copy_info__addnew(kci, fields)
> > 
> > I would do it as:
> > 
> > struct phdr_data *phdr_data__new(fields)
> > {
> > 	return  zalloc() + init fields;
> > }
> > 
> > struct phdr_data *kcore_copy_info__addnew(kci, fields)
> > {
> > 	struct phdr_data *pd = phdr_data__new(fields);
> > 
> > 	if (pd)
> > 		list_add(&pd->list, &kci->phdrs)
> > }
> > 
> > Also please rename pd->list to pd->node, to clarify that it is a node in
> > some list, not a list.
> > 
> > The commit log list then could reflect that somehow, with something
> > around:
> > 
> > ----------------------
> > 
> > Move ->kernel_map and ->modules_map to newly allocated entries in the
> > ->phdrs list.
> > 
> > ----------------------
> > 
> > wdyt?
> 
> I have done the changes but still have kcore_copy__map() calling
> kcore_copy_info__addnew().  The changes have been pushed to the same branch.

Thanks! I'll process a perf/urgent round and then go over your updated
tree to get it tested on a skylake machine and merged to perf/core,

- arnaldo