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SubjectRe: [RFC, PATCH 07/22] x86/mm: Mask out KeyID bits from page table entry pfn
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Hi Kirill,

A flyby comment below.

"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes:

> MKTME claims several upper bits of the physical address in a page table
> entry to encode KeyID. It effectively shrinks number of bits for
> physical address. We should exclude KeyID bits from physical addresses.
>
> For instance, if CPU enumerates 52 physical address bits and number of
> bits claimed for KeyID is 6, bits 51:46 must not be threated as part
> physical address.
>
> This patch adjusts __PHYSICAL_MASK during MKTME enumeration.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
> arch/x86/kernel/cpu/intel.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index c770689490b5..35436bbadd0b 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -580,6 +580,30 @@ static void detect_tme(struct cpuinfo_x86 *c)
> mktme_status = MKTME_ENABLED;
> }
>
> +#ifdef CONFIG_X86_INTEL_MKTME
> + if (mktme_status == MKTME_ENABLED && nr_keyids) {
> + /*
> + * Mask out bits claimed from KeyID from physical address mask.
> + *
> + * For instance, if a CPU enumerates 52 physical address bits
> + * and number of bits claimed for KeyID is 6, bits 51:46 of
> + * physical address is unusable.
> + */
> + phys_addr_t keyid_mask;
> +
> + keyid_mask = 1ULL << c->x86_phys_bits;
> + keyid_mask -= 1ULL << (c->x86_phys_bits - keyid_bits);
> + physical_mask &= ~keyid_mask;

You could use GENMASK_ULL() to construct the keyid_mask instead of
rolling your own here.

Thanks,
Punit


> + } else {
> + /*
> + * Reset __PHYSICAL_MASK.
> + * Maybe needed if there's inconsistent configuation
> + * between CPUs.
> + */
> + physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
> + }
> +#endif
> +
> /*
> * Exclude KeyID bits from physical address bits.
> *

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