[PATCH] x86/kexec: do not reserve kexec setup_data in kexec e820 table

[PATCH] x86/kexec: do not reserve kexec setup_data in kexec e820 table

[Dave Young]

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@redhat.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) {

Re: [PATCH] x86/kexec: do not reserve kexec setup_data in kexec e820 table

[Dave Young]

On 02/12/20 at 07:04pm, Dave Young wrote:
> 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@redhat.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) {

Ping, can someone review this? It caused fragmented memory in kexec
kernel also waste memory.

Thanks
Dave

[tip: x86/kdump] x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

[tip-bot2 for Dave Young]

The following commit has been merged into the x86/kdump branch of tip:

Commit-ID:     8efbc518b884e1db2dd6a6fce62d0112ab871dcf
Gitweb:        https://git.kernel.org/tip/8efbc518b884e1db2dd6a6fce62d0112ab871dcf
Author:        Dave Young <dyoung@redhat.com>
AuthorDate:    Wed, 12 Feb 2020 19:04:24 +08:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 24 Feb 2020 11:41:57 +01:00

x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

The e820 table for the kexec kernel unconditionally marks setup_data as
reserved because the second kernel can reuse setup_data passed by the
1st kernel's boot loader, for example SETUP_PCI marked regions like PCI
BIOS, etc.

SETUP_EFI types, however, are used by kexec itself to enable EFI in the
2nd kernel. Thus, it is pointless to add this type of setup_data to the
kexec e820 table as reserved.

IOW, what happens is this:

  -  1st physical boot: no SETUP_EFI.

  - kexec loads a new kernel and prepares a SETUP_EFI setup_data blob, then
  reboots the machine.

  - 2nd kernel sees SETUP_EFI, reserves it both in the e820 and in the
  kexec e820 table.

  - If another kexec load is executed, it prepares a new SETUP_EFI blob and
  then reboots the machine into the new kernel.

  5. The 3rd kexec-ed kernel has two SETUP_EFI ranges reserved. And so on...

Thus skip SETUP_EFI while reserving setup_data in the e820_table_kexec
table because it is not needed.

 [ bp: Heavily massage commit message, shorten line and improve comment. ]

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200212110424.GA2938@dhcp-128-65.nay.redhat.com
---
 arch/x86/kernel/e820.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index c5399e8..c920296 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -999,7 +999,15 @@ void __init e820__reserve_setup_data(void)
 	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);
+
+		/*
+		 * SETUP_EFI is supplied by kexec and does not need to be
+		 * reserved.
+		 */
+		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) {

Re: [tip: x86/kdump] x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

[Dave Young]

On 02/24/20 at 10:51am, tip-bot2 for Dave Young wrote:
> The following commit has been merged into the x86/kdump branch of tip:
> 
> Commit-ID:     8efbc518b884e1db2dd6a6fce62d0112ab871dcf
> Gitweb:        https://git.kernel.org/tip/8efbc518b884e1db2dd6a6fce62d0112ab871dcf
> Author:        Dave Young <dyoung@redhat.com>
> AuthorDate:    Wed, 12 Feb 2020 19:04:24 +08:00
> Committer:     Borislav Petkov <bp@suse.de>
> CommitterDate: Mon, 24 Feb 2020 11:41:57 +01:00
> 
> x86/kexec: Do not reserve EFI setup_data in the kexec e820 table
> 
> The e820 table for the kexec kernel unconditionally marks setup_data as
> reserved because the second kernel can reuse setup_data passed by the
> 1st kernel's boot loader, for example SETUP_PCI marked regions like PCI
> BIOS, etc.
> 
> SETUP_EFI types, however, are used by kexec itself to enable EFI in the
> 2nd kernel. Thus, it is pointless to add this type of setup_data to the
> kexec e820 table as reserved.
> 
> IOW, what happens is this:
> 
>   -  1st physical boot: no SETUP_EFI.
> 
>   - kexec loads a new kernel and prepares a SETUP_EFI setup_data blob, then
>   reboots the machine.
> 
>   - 2nd kernel sees SETUP_EFI, reserves it both in the e820 and in the
>   kexec e820 table.
> 
>   - If another kexec load is executed, it prepares a new SETUP_EFI blob and
>   then reboots the machine into the new kernel.
> 
>   5. The 3rd kexec-ed kernel has two SETUP_EFI ranges reserved. And so on...
> 
> Thus skip SETUP_EFI while reserving setup_data in the e820_table_kexec
> table because it is not needed.
> 
>  [ bp: Heavily massage commit message, shorten line and improve comment. ]

Boris, thanks for the amending and log massage.
I was hesitating to break the long line or not and then I choosed
leaving it as is.  Both are not very good and either of them is fine to me.

Thanks
Dave