From: Ard Biesheuvel <ardb@kernel.org>

Since commit

  d9ec1158056b ("x86/boot/64: Use RIP_REL_REF() to assign 'phys_base'")

phys_base is assigned directly rather than added to, so it is no longer
necessary to clear it after use.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/platform/pvh/head.S | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index f09e0fb832e4..592747f2d731 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -179,13 +179,6 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	ANNOTATE_RETPOLINE_SAFE
 	call *%rax
 
-	/*
-	 * Clear phys_base.  __startup_64 will *add* to its value,
-	 * so reset to 0.
-	 */
-	xor  %rbx, %rbx
-	movq %rbx, phys_base(%rip)
-
 	/* startup_64 expects boot_params in %rsi. */
 	lea pvh_bootparams(%rip), %rsi
 	jmp startup_64
-- 
2.46.0.792.g87dc391469-goog

On 2024-09-26 06:41, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> Since commit
> 
>    d9ec1158056b ("x86/boot/64: Use RIP_REL_REF() to assign 'phys_base'")
> 
> phys_base is assigned directly rather than added to, so it is no longer
> necessary to clear it after use.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Tested-by: Jason Andryuk <jason.andryuk@amd.com>

My patch pre-dated the above, but I never liked it.  Happy to see this gone.

Thanks,
Jason