2024-01-31 23:27:09

by Paolo Bonzini

Subject: [PATCH v2 1/2] 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")
Cc: Adam Dunlap <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Xiaoyao Li <[email protected]>
Cc: Kai Huang <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
---
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 0b97bcde70c6..fbc4e60d027c 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);
--
2.43.0

2024-02-01 14:55:44

by Kirill A. Shutemov

Subject: Re: [PATCH v2 1/2] x86/cpu: allow reducing x86_phys_bits during early_identify_cpu()

On Thu, Feb 01, 2024 at 12:09:01AM +0100, Paolo Bonzini wrote:
> 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")
> Cc: Adam Dunlap <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
> Cc: Xiaoyao Li <[email protected]>
> Cc: Kai Huang <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>

Reviewed-by: Kirill A. Shutemov <[email protected]>

--
Kiryl Shutsemau / Kirill A. Shutemov

2024-02-01 15:56:20

by Kai Huang

Subject: Re: [PATCH v2 1/2] x86/cpu: allow reducing x86_phys_bits during early_identify_cpu()

On 1/02/2024 7:09 am, Paolo Bonzini wrote:
> 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")
> Cc: Adam Dunlap <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
> Cc: Xiaoyao Li <[email protected]>
> Cc: Kai Huang <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>

Acked-by: Kai Huang <[email protected]>