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[PATCH 05/29] x86/boot/e820: Print gaps in the E820 table

Ingo Molnar posted 29 patches 7 months, 4 weeks ago
There is a newer version of this series
[PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Ingo Molnar 7 months, 4 weeks ago 
Gaps in the E820 table are not obvious at a glance and can
easily be overlooked.

Print out gaps in the E820 table:

Before:

	BIOS-provided physical RAM map:
	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
After:

	BIOS-provided physical RAM map:
	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved

Also warn about badly ordered E820 table entries:

	BUG: out of order E820 entry!

( this is printed before the entry is printed, so there's no need to
  print any additional data with the warning. )

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/kernel/e820.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 4244b6d53fd0..a8edfa375fbd 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -201,18 +201,32 @@ static void __init e820_print_type(enum e820_type type)
 
 static void __init e820__print_table(const char *who)
 {
+	u64 range_end_prev = 0;
 	int i;
 
 	for (i = 0; i < e820_table->nr_entries; i++) {
 		struct e820_entry *entry = e820_table->entries + i;
+		u64 range_start, range_end;
 
-		pr_info("%s: [mem %#018Lx-%#018Lx] ",
-			who,
-			entry->addr,
-			entry->addr + entry->size-1);
+		range_start = entry->addr;
+		range_end   = entry->addr + entry->size;
 
+		/* Out of order E820 maps should not happen: */
+		if (range_start < range_end_prev)
+			pr_info("BUG: out of order E820 entry!\n");
+
+		if (range_start > range_end_prev) {
+			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
+				who,
+				range_end_prev,
+				range_start-1);
+		}
+
+		pr_info("%s: [mem %#018Lx-%#018Lx] ", who, range_start, range_end-1);
 		e820_print_type(entry->type);
 		pr_cont("\n");
+
+		range_end_prev = range_end;
 	}
 }
 
-- 
2.45.2
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Andy Shevchenko 7 months, 4 weeks ago 
Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar kirjoitti:
> Gaps in the E820 table are not obvious at a glance and can
> easily be overlooked.
> 
> Print out gaps in the E820 table:
> 
> Before:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> After:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> 
> Also warn about badly ordered E820 table entries:
> 
> 	BUG: out of order E820 entry!
> 
> ( this is printed before the entry is printed, so there's no need to
>   print any additional data with the warning. )

...

> +		u64 range_start, range_end;

struct range (from range.h) and...

> +		range_start = entry->addr;
> +		range_end   = entry->addr + entry->size;
>  
> +		/* Out of order E820 maps should not happen: */
> +		if (range_start < range_end_prev)
> +			pr_info("BUG: out of order E820 entry!\n");
> +
> +		if (range_start > range_end_prev) {
> +			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
> +				who,
> +				range_end_prev,
> +				range_start-1);

%pra
with who mentioned the "gap"?

> +		}

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Ingo Molnar 7 months ago 
* Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar kirjoitti:
> > Gaps in the E820 table are not obvious at a glance and can
> > easily be overlooked.
> > 
> > Print out gaps in the E820 table:
> > 
> > Before:
> > 
> > 	BIOS-provided physical RAM map:
> > 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> > 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> > 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> > 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> > 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> > 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> > 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> > 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> > 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> > 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> > After:
> > 
> > 	BIOS-provided physical RAM map:
> > 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> > 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> > 	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
> > 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> > 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> > 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> > 	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
> > 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> > 	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
> > 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> > 	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
> > 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> > 	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
> > 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> > 	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
> > 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> > 
> > Also warn about badly ordered E820 table entries:
> > 
> > 	BUG: out of order E820 entry!
> > 
> > ( this is printed before the entry is printed, so there's no need to
> >   print any additional data with the warning. )
> 
> ...
> 
> > +		u64 range_start, range_end;
> 
> struct range (from range.h) and...

Yeah, using those primitives makes sense, but right now the e820 code 
isn't using them, and it's better to have similar & unified range 
handling code patterns.

In principle I wouldn't be opposed to patches that convert the e820 
code to <linux/range.h> types.

> 
> > +		range_start = entry->addr;
> > +		range_end   = entry->addr + entry->size;
> >  
> > +		/* Out of order E820 maps should not happen: */
> > +		if (range_start < range_end_prev)
> > +			pr_info("BUG: out of order E820 entry!\n");
> > +
> > +		if (range_start > range_end_prev) {
> > +			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
> > +				who,
> > +				range_end_prev,
> > +				range_start-1);
> 
> %pra

This would be part of any <linux/range.h> conversion patches.

> with who mentioned the "gap"?

Not sure I understand?

Thanks,

	Ingo
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Andy Shevchenko 7 months ago 
On Thu, May 15, 2025 at 12:28:13PM +0200, Ingo Molnar wrote:
> * Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> > Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar kirjoitti:

...

> > > +		u64 range_start, range_end;
> > 
> > struct range (from range.h) and...
> 
> Yeah, using those primitives makes sense, but right now the e820 code 
> isn't using them, and it's better to have similar & unified range 
> handling code patterns.
> 
> In principle I wouldn't be opposed to patches that convert the e820 
> code to <linux/range.h> types.

Okay, perhaps a separate cleanup in the future. Not sure if I will have time,
but let's see...

...

> > > +		if (range_start > range_end_prev) {
> > > +			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
> > > +				who,
> > > +				range_end_prev,
> > > +				range_start-1);
> > 
> > %pra
> 
> This would be part of any <linux/range.h> conversion patches.
> 
> > with who mentioned the "gap"?
> 
> Not sure I understand?

With the range.h in place and the mentioned specifier, the above will be like

BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
BIOS-e820: [range 0x00000000000a0000-0x00000000000effff] gap
BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Mike Rapoport 7 months, 4 weeks ago 
On Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar wrote:
> Gaps in the E820 table are not obvious at a glance and can
> easily be overlooked.
> 
> Print out gaps in the E820 table:
> 
> Before:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> After:
> 
> 	BIOS-provided physical RAM map:
> 	BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> 	BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> 	BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff]
> 	BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> 	BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable
> 	BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved
> 	BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff]
> 	BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved
> 	BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff]
> 	BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> 	BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff]
> 	BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
> 	BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff]
> 	BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
> 	BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff]
> 	BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved
> 
> Also warn about badly ordered E820 table entries:
> 
> 	BUG: out of order E820 entry!
> 
> ( this is printed before the entry is printed, so there's no need to
>   print any additional data with the warning. )
> 
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: Arnd Bergmann <arnd@kernel.org>
> Cc: David Woodhouse <dwmw@amazon.co.uk>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  arch/x86/kernel/e820.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 4244b6d53fd0..a8edfa375fbd 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -201,18 +201,32 @@ static void __init e820_print_type(enum e820_type type)
>  
>  static void __init e820__print_table(const char *who)
>  {
> +	u64 range_end_prev = 0;
>  	int i;
>  
>  	for (i = 0; i < e820_table->nr_entries; i++) {
>  		struct e820_entry *entry = e820_table->entries + i;
> +		u64 range_start, range_end;
>  
> -		pr_info("%s: [mem %#018Lx-%#018Lx] ",
> -			who,
> -			entry->addr,
> -			entry->addr + entry->size-1);
> +		range_start = entry->addr;
> +		range_end   = entry->addr + entry->size;
>  
> +		/* Out of order E820 maps should not happen: */
> +		if (range_start < range_end_prev)
> +			pr_info("BUG: out of order E820 entry!\n");

Maybe "BIOS BUG"?

> +
> +		if (range_start > range_end_prev) {
> +			pr_info("%s: [gap %#018Lx-%#018Lx]\n",
> +				who,
> +				range_end_prev,
> +				range_start-1);

range_start - 1 ;-)

> +		}
> +
> +		pr_info("%s: [mem %#018Lx-%#018Lx] ", who, range_start, range_end-1);
>  		e820_print_type(entry->type);
>  		pr_cont("\n");
> +
> +		range_end_prev = range_end;
>  	}
>  }
>  
> -- 
> 2.45.2
> 

-- 
Sincerely yours,
Mike.
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Andy Shevchenko 7 months, 4 weeks ago 
Tue, Apr 22, 2025 at 09:00:00AM +0300, Mike Rapoport kirjoitti:
> On Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar wrote:

...

> > +		if (range_start < range_end_prev)
> > +			pr_info("BUG: out of order E820 entry!\n");
> 
> Maybe "BIOS BUG"?

FWIW, we have FW_BUG definition, with that

			pr_info(FW_BUG "out of order E820 entry!\n");

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH 05/29] x86/boot/e820: Print gaps in the E820 table
Posted by Ingo Molnar 7 months ago 
* Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> Tue, Apr 22, 2025 at 09:00:00AM +0300, Mike Rapoport kirjoitti:
> > On Mon, Apr 21, 2025 at 08:51:45PM +0200, Ingo Molnar wrote:
> 
> ...
> 
> > > +		if (range_start < range_end_prev)
> > > +			pr_info("BUG: out of order E820 entry!\n");
> > 
> > Maybe "BIOS BUG"?
> 
> FWIW, we have FW_BUG definition, with that
> 
> 			pr_info(FW_BUG "out of order E820 entry!\n");

Agreed, I've folded in the change below.

Thanks,

	Ingo

=============================>
 arch/x86/kernel/e820.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 36b74b233bd6..c8833ac9cbf9 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -213,7 +213,7 @@ static void __init e820__print_table(const char *who)
 
 		/* Out of order E820 maps should not happen: */
 		if (range_start < range_end_prev)
-			pr_info("BUG: out of order E820 entry!\n");
+			pr_info(FW_BUG "out of order E820 entry!\n");
 
 		if (range_start > range_end_prev) {
 			pr_info("%s: [gap %#018Lx-%#018Lx]\n",

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