linux-kernel - Re: [PATCH v15 3/6] x86/boot: Introduce efi_get_rsdp

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Date:   Fri, 11 Jan 2019 11:32:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, keescook@...omium.org,
        bhe@...hat.com, msys.mizuma@...il.com, indou.takao@...fujitsu.com,
        caoj.fnst@...fujitsu.com
Subject: Re: [PATCH v15 3/6] x86/boot: Introduce efi_get_rsdp_addr() to find
 RSDP from EFI table

On Fri, Jan 11, 2019 at 09:23:53AM +0800, Chao Fan wrote:
> Yes, 'table64' looks superfluous here, but after these lines, there is:
>                         if (!IS_ENABLED(CONFIG_X86_64) && table64 >> 32) {
> so the 'table64' is useful here for i386. 'table' is unsigned long, it
> can't do the right shift. But the 'table64' who is u64 can do that right
> shift.

Have you actually tried fixing what I suggested or you're just talking?

---
diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index e9dd84f459ed..0537d46fb21f 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -77,21 +77,19 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 			sizeof(efi_config_table_32_t);
 
 	for (i = 0; i < systab->nr_tables; i++) {
+		acpi_physical_address table;
 		void *config_tables;
-		unsigned long table;
 		efi_guid_t guid;
 
 		config_tables = (void *)(systab->tables + size * i);
 		if (efi_64) {
 			efi_config_table_64_t *tmp_table;
-			u64 table64;
 
 			tmp_table = config_tables;
 			guid = tmp_table->guid;
-			table64 = tmp_table->table;
-			table = table64;
+			table = tmp_table->table;
 
-			if (!IS_ENABLED(CONFIG_X86_64) && table64 >> 32) {
+			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
 				debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
 				return 0;
 			}

-- 
Regards/Gruss,
    Boris.

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