[v2] x86/boot: Setup correctly fs segment for bogus_real_magic

[PATCH v2] x86/boot: Setup correctly fs segment for bogus_real_magic

Frediano Ziglio posted 1 patch 11 months, 3 weeks ago

Diff against v1 v3
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git fetch https://gitlab.com/xen-project/patchew/xen tags/patchew/20241111111822.6795-1-frediano.ziglio@cloud.com

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xen/arch/x86/boot/wakeup.S | 2 ++
1 file changed, 2 insertions(+)

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[PATCH v2] x86/boot: Setup correctly fs segment for bogus_real_magic

Posted by Frediano Ziglio 11 months, 3 weeks ago

bogus_real_magic code uses fs segment so it should be initialised.

Fixes: d8c8fef09054 ("Provide basic Xen PM infrastructure")
Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
---
Changes since v1:
- added "Fixes" comment;
- add initialisation, do not remove old one.
---
 xen/arch/x86/boot/wakeup.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/boot/wakeup.S b/xen/arch/x86/boot/wakeup.S
index 08447e1934..99ac8594b8 100644
--- a/xen/arch/x86/boot/wakeup.S
+++ b/xen/arch/x86/boot/wakeup.S
@@ -20,6 +20,8 @@ ENTRY(wakeup_start)
         movw    %ax, %ds
         movw    %ax, %ss        # A stack required for BIOS call
         movw    $wakesym(wakeup_stack), %sp
+        movw    $0xb800, %ax
+        movw    %ax, %fs
 
         pushl   $0              # Kill dangerous flag early
         popfl
-- 
2.34.1

Re: [PATCH v2] x86/boot: Setup correctly fs segment for bogus_real_magic

Posted by Jan Beulich 11 months, 3 weeks ago

On 11.11.2024 12:18, Frediano Ziglio wrote:
> --- a/xen/arch/x86/boot/wakeup.S
> +++ b/xen/arch/x86/boot/wakeup.S
> @@ -20,6 +20,8 @@ ENTRY(wakeup_start)
>          movw    %ax, %ds
>          movw    %ax, %ss        # A stack required for BIOS call
>          movw    $wakesym(wakeup_stack), %sp
> +        movw    $0xb800, %ax
> +        movw    %ax, %fs
>  
>          pushl   $0              # Kill dangerous flag early
>          popfl

If put here, I think it needs to be accompanied by a comment, to avoid
it (wrongly) being deemed redundant again. Personally I would prefer if
it was put where it's needed, at bogus_real_magic itself (at which
point no commentary would be needed).

Jan