x86/pvh: Omit needless clearing of phys_base

Since commit

  d9ec115 ("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.

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Tested-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Message-ID: <20241009160438.3884381-10-ardb+git@google.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

Author: ardbiesheuvel

arch/x86/platform/pvh/head.S

@@ -180,13 +180,6 @@ 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