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Date: Tue, 30 Jan 2024 21:33:54 +0000
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Subject: Re: Reserved bits and commit x86/sev-es: Set x86_virt_bits to the
 correct value straight away, instead of a two-phase approach
From: Jacob Xu <jacobhxu@google.com>
To: jeremy.compostella@intel.com
Cc: acdunlap@google.com, Thomas.Lendacky@amd.com, michael.roth@amd.com, 
	ashish.kalra@amd.com, bp@alien8.de, felix-coreboot@felixheld.de, 
	kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, 
	mingo@kernel.org, x86@kernel.org
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Adding some AMD folk to the thread here.

For AMD CPUs, initialization of c->x86_phys_bits occurs in
get_cpu_address_sizes() which is called from early_identify_cpu().

However, early_identify_cpu() will first call early_init_amd() which adjusts
x86_phys_bits based on the PhysAddrReduction CPUID field.

c->x86_phys_bits -= (cpuid_ebx(0x8000001f) >> 6) & 0x3f;

Thus, this adjustment is ignored.

Adding a new cpu_dev callback to calculate num reserved_cpu_bits makes sense to
me, hopefully the AMD folk can chime in here though.

Jacob