diff mbox series

[repost] x86/boot: Add a message about ignored early NMIs

Message ID ZaEe8FC767f+sxRQ@jeru.linux.bs1.fc.nec.co.jp
State New
Headers
Series [repost] x86/boot: Add a message about ignored early NMIs |

Commit Message

NOMURA JUNICHI(野村 淳一) Jan. 12, 2024, 11:13 a.m. UTC 
  Commit 78a509fba9c9 ("x86/boot: Ignore NMIs during very early boot") added
empty handler in early boot stage to avoid boot failure by spurious NMIs.

Add a diagnostic message in case we need to know whether early NMIs have
occurred and/or what happened to them.

Signed-off-by: Jun'ichi Nomura <junichi.nomura@nec.com>
Suggested-by: Borislav Petkov <bp@alien8.de>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Link: https://lore.kernel.org/lkml/20231130103339.GCZWhlA196uRklTMNF@fat_crate.local/

Comments

Kirill A. Shutemov Jan. 12, 2024, 12:06 p.m. UTC | #1 
On Fri, Jan 12, 2024 at 11:13:53AM +0000, NOMURA JUNICHI(野村 淳一) wrote:
> Commit 78a509fba9c9 ("x86/boot: Ignore NMIs during very early boot") added
> empty handler in early boot stage to avoid boot failure by spurious NMIs.
> 
> Add a diagnostic message in case we need to know whether early NMIs have
> occurred and/or what happened to them.
> 
> Signed-off-by: Jun'ichi Nomura <junichi.nomura@nec.com>
> Suggested-by: Borislav Petkov <bp@alien8.de>
> Suggested-by: H. Peter Anvin <hpa@zytor.com>
> Link: https://lore.kernel.org/lkml/20231130103339.GCZWhlA196uRklTMNF@fat_crate.local/
> 
> diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
> --- a/arch/x86/boot/compressed/ident_map_64.c
> +++ b/arch/x86/boot/compressed/ident_map_64.c
> @@ -387,7 +387,10 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
>  	kernel_add_identity_map(address, end);
>  }
>  
> +extern int spurious_nmi_count;
> +

It has to be in a header file.

>  void do_boot_nmi_trap(struct pt_regs *regs, unsigned long error_code)
>  {
>  	/* Empty handler to ignore NMI during early boot */
> +	spurious_nmi_count++;
>  }
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -357,6 +357,8 @@ unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
>  	return entry;
>  }
>  
> +int spurious_nmi_count;
> +

It is not a right place to define a variable. Do it next to rest of
variables at the beginning of the file.
>  /*
>   * The compressed kernel image (ZO), has been moved so that its position
>   * is against the end of the buffer used to hold the uncompressed kernel
> @@ -493,6 +495,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
>  	/* Disable exception handling before booting the kernel */
>  	cleanup_exception_handling();
>  
> +	if (spurious_nmi_count) {
> +		error_putstr("Spurious early NMI ignored. Number of NMIs: 0x");
> +		error_puthex(spurious_nmi_count);
> +		error_putstr("\n");
> +	}
> +
>  	return output + entry_offset;
>  }
>
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -387,7 +387,10 @@  void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
 	kernel_add_identity_map(address, end);
 }
 
+extern int spurious_nmi_count;
+
 void do_boot_nmi_trap(struct pt_regs *regs, unsigned long error_code)
 {
 	/* Empty handler to ignore NMI during early boot */
+	spurious_nmi_count++;
 }
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -357,6 +357,8 @@  unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
 	return entry;
 }
 
+int spurious_nmi_count;
+
 /*
  * The compressed kernel image (ZO), has been moved so that its position
  * is against the end of the buffer used to hold the uncompressed kernel
@@ -493,6 +495,12 @@  asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
 	/* Disable exception handling before booting the kernel */
 	cleanup_exception_handling();
 
+	if (spurious_nmi_count) {
+		error_putstr("Spurious early NMI ignored. Number of NMIs: 0x");
+		error_puthex(spurious_nmi_count);
+		error_putstr("\n");
+	}
+
 	return output + entry_offset;
 }