linux-kernel - [tip: x86/urgent] x86/cpu: Allow reducing x86_phys_bits during early_identify

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Date: Mon, 26 Feb 2024 18:44:55 -0000
From: "tip-bot2 for Paolo Bonzini" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, stable@...r.kernel.org,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/cpu: Allow reducing x86_phys_bits during
 early_identify_cpu()

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     9a458198eba98b7207669a166e64d04b04cb651b
Gitweb:        https://git.kernel.org/tip/9a458198eba98b7207669a166e64d04b04cb651b
Author:        Paolo Bonzini <pbonzini@...hat.com>
AuthorDate:    Thu, 01 Feb 2024 00:09:01 +01:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Mon, 26 Feb 2024 08:16:15 -08:00

x86/cpu: Allow reducing x86_phys_bits during early_identify_cpu()

In commit fbf6449f84bf ("x86/sev-es: Set x86_virt_bits to the correct
value straight away, instead of a two-phase approach"), the initialization
of c->x86_phys_bits was moved after this_cpu->c_early_init(c).  This is
incorrect because early_init_amd() expected to be able to reduce the
value according to the contents of CPUID leaf 0x8000001f.

Fortunately, the bug was negated by init_amd()'s call to early_init_amd(),
which does reduce x86_phys_bits in the end.  However, this is very
late in the boot process and, most notably, the wrong value is used for
x86_phys_bits when setting up MTRRs.

To fix this, call get_cpu_address_sizes() as soon as X86_FEATURE_CPUID is
set/cleared, and c->extended_cpuid_level is retrieved.

Fixes: fbf6449f84bf ("x86/sev-es: Set x86_virt_bits to the correct value straight away, instead of a two-phase approach")
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc:stable@...r.kernel.org
Link: https://lore.kernel.org/all/20240131230902.1867092-2-pbonzini%40redhat.com
---
 arch/x86/kernel/cpu/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0b97bcd..fbc4e60 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1589,6 +1589,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		get_cpu_vendor(c);
 		get_cpu_cap(c);
 		setup_force_cpu_cap(X86_FEATURE_CPUID);
+		get_cpu_address_sizes(c);
 		cpu_parse_early_param();
 
 		if (this_cpu->c_early_init)
@@ -1601,10 +1602,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 			this_cpu->c_bsp_init(c);
 	} else {
 		setup_clear_cpu_cap(X86_FEATURE_CPUID);
+		get_cpu_address_sizes(c);
 	}
 
-	get_cpu_address_sizes(c);
-
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 
 	cpu_set_bug_bits(c);