linux-kernel - Re: [PATCH] resource,kexec: walk_system_ram_res

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Message-ID: <ZxKBFMAecrL25Fwb@MiWiFi-R3L-srv>
Date: Fri, 18 Oct 2024 23:39:00 +0800
From: Baoquan He <bhe@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Gregory Price <gourry@...rry.net>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	bhelgaas@...gle.com, ilpo.jarvinen@...ux.intel.com,
	mika.westerberg@...ux.intel.com, ying.huang@...el.com,
	tglx@...utronix.de, takahiro.akashi@...aro.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] resource,kexec: walk_system_ram_res_rev must retain
 resource flags

On 10/18/24 at 05:52pm, Andy Shevchenko wrote:
> On Fri, Oct 18, 2024 at 05:51:09PM +0300, Andy Shevchenko wrote:
> > On Fri, Oct 18, 2024 at 09:52:47PM +0800, Baoquan He wrote:
> > > On 10/18/24 at 03:22pm, Andy Shevchenko wrote:
> > > > On Fri, Oct 18, 2024 at 10:18:42AM +0800, Baoquan He wrote:
> > > > > On 10/17/24 at 03:03pm, Gregory Price wrote:
> > > > > > walk_system_ram_res_rev() erroneously discards resource flags when
> > > > > > passing the information to the callback.
> > > > > > 
> > > > > > This causes systems with IORESOURCE_SYSRAM_DRIVER_MANAGED memory to
> > > > > > have these resources selected during kexec to store kexec buffers
> > > > > > if that memory happens to be at placed above normal system ram.
> > > > > 
> > > > > Sorry about that. I haven't checked IORESOURCE_SYSRAM_DRIVER_MANAGED
> > > > > memory carefully, wondering if res could be set as
> > > > > 'IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY' plus
> > > > > IORESOURCE_SYSRAM_DRIVER_MANAGED in iomem_resource tree.
> > > > > 
> > > > > Anyway, the change in this patch is certainly better. Thanks.
> > > > 
> > > > Can we get more test cases in the respective module, please?
> > > 
> > > Do you mean testing CXL memory in kexec/kdump? No, we can't. Kexec/kdump
> > > test cases basically is system testing, not unit test or module test. It
> > > needs run system and then jump to 2nd kernel, vm can be used but it
> > > can't cover many cases existing only on baremetal. Currenly, Redhat's
> > > CKI is heavily relied on to test them, however I am not sure if system
> > > with CXL support is available in our LAB.
> > > 
> > > Not sure if I got you right.
> > 
> > I meant since we touch resource.c, we should really touch resource_kunit.c
> > *in addition to*.
> 
> And to be more clear, there is no best time to add test cases than
> as early as possible. So, can we add the test cases to the (new) APIs,
> so we want have an issue like the one this patch fixes?

I will have a look at kernel/resource_kunit.c to see if I can add
something for walk_system_ram_res_rev(). Thanks.