linux-kernel - Re: [PATCH 2/2] x86/kexec_file: add reserved e820 ranges to 2nd kernel e820 table

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Date:   Tue, 18 Sep 2018 19:15:14 +0800
From:   Dave Young <dyoung@...hat.com>
To:     lijiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH 2/2] x86/kexec_file: add reserved e820 ranges to 2nd
 kernel e820 table

On 09/18/18 at 06:20pm, lijiang wrote:
> 在 2018年09月18日 11:20, Dave Young 写道:
> > On 09/18/18 at 10:48am, Lianbo Jiang wrote:
> >> e820 reserved ranges is useful in kdump kernel, we have added this in
> >> kexec-tools code.
> >>
> >> One reason is PCI mmconf (extended mode) requires reserved region
> >> otherwise it falls back to legacy mode.
> >>
> >> When AMD SME kdump support, it needs to map dmi table area as unencrypted.
> >> For normal boot these ranges sit in e820 reserved ranges thus the early
> >> ioremap code naturally map them as unencrypted. So if we have same e820
> >> reserve setup in kdump kernel then it will just work like normal kernel.
> >>
> >> Signed-off-by: Dave Young <dyoung@...hat.com>
> >> Signed-off-by: Lianbo Jiang <lijiang@...hat.com>
> >> ---
> >>  arch/x86/kernel/crash.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>
> >> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> >> index 3c113e6545a3..db453e9c117b 100644
> >> --- a/arch/x86/kernel/crash.c
> >> +++ b/arch/x86/kernel/crash.c
> >> @@ -384,6 +384,12 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
> >>  	walk_iomem_res_desc(IORES_DESC_ACPI_NV_STORAGE, flags, 0, -1, &cmd,
> >>  			memmap_entry_callback);
> >>  
> >> +	/* Add all reserved ranges */
> >> +	cmd.type = E820_TYPE_RESERVED;
> >> +	flags = IORESOURCE_MEM;
> > 
> > Lianbo, rethink about this, we will miss other io resource types if only
> > match IORESOURCE_MEM here, can you redo the patch with just using "0"
> > for the passing flags?
> > 
> 
> This patches align on kexec-tools for e820 reserved ranges, if so, the kexec-tools also need to
> be improved for the other type, such as IORESOURCE_IO/BUS/DMA(...), right?

Kexec-tools just go through /proc/iomem "reserved" items and add them
these flags are not visible to it.  So we have done same in kexec-tools.

> 
> I will improve these patches and post v2 tomorrow.

Thanks!
Dave