linux-kernel - [PATCH] x86/kexec: do not reserve kexec setup

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Message-ID: <20200212110424.GA2938@dhcp-128-65.nay.redhat.com>
Date:   Wed, 12 Feb 2020 19:04:24 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: [PATCH] x86/kexec: do not reserve kexec setup_data in kexec e820
 table

The e820 table for kexec kernel always takes setup_data as reserved.
It is reasonable for the setup_data passed by the 1st kernel boot loader,
for example SETUP_PCI etc.  But SETUP_EFI is used by kexec itself to
enable EFI in 2nd kernel, also kexec setups it every time. Thus it
is pointless to reserve kexec prepared setup_data.

1st physical boot: no SETUP_EFI
kexec load new kernel and prepare a SETUP_EFI setup_data, then reboot
 -> 2nd kernel sees SETUP_EFI, reserves in both e820 and kexec e820
    another kexec load prepare a new SETUP_EFI, then reboot
    -> 3rd kernel has two SETUP_EFI ranges reserved
       -> and so on..

Thus skip SETUP_EFI while reserving setup_data for kexec kernel.

Signed-off-by: Dave Young <dyoung@...hat.com>
---
 arch/x86/kernel/e820.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- linux-x86.orig/arch/x86/kernel/e820.c
+++ linux-x86/arch/x86/kernel/e820.c
@@ -999,7 +999,9 @@ void __init e820__reserve_setup_data(voi
 	while (pa_data) {
 		data = early_memremap(pa_data, sizeof(*data));
 		e820__range_update(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
-		e820__range_update_kexec(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
+		/* Skip kexec passed setup_data */
+		if (data->type != SETUP_EFI)
+			e820__range_update_kexec(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
 
 		if (data->type == SETUP_INDIRECT &&
 		    ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {