On 9/5/19 5:59 PM, Dave Hansen wrote:
On 9/5/19 8:21 AM, Thomas Hellström (VMware) wrote:
#define pgprot_modify pgprot_modify
static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t
newprot)
{
- pgprotval_t preservebits = pgprot_val(oldprot) & _PAGE_CHG_MASK;
- pgprotval_t addbits = pgprot_val(newprot);
+ pgprotval_t preservebits = pgprot_val(oldprot) &
+ (_PAGE_CHG_MASK | sme_me_mask);
+ pgprotval_t addbits = pgprot_val(newprot) & ~sme_me_mask;
return __pgprot(preservebits | addbits);
}
_PAGE_CHG_MASK is claiming similar functionality about preserving bits
when changing PTEs:
...
#define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT
| \
_PAGE_SPECIAL | _PAGE_ACCESSED |
_PAGE_DIRTY | \
_PAGE_SOFT_DIRTY | _PAGE_DEVMAP)
This makes me wonder if we should be including sme_me_mask in
_PAGE_CHG_MASK (logically).
I was thinking the same. But what confuses me is that addbits isn't
masked with ~_PAGE_CHG_MASK, which is needed for sme_me_mask, since the
problem otherwise is typically that the encryption bit is incorrectly
set in addbits. I wonder whether it's an optimization or intentional.
I think there's a built-in assumption that 'newprot' won't have any of
the _PAGE_CHG_MASK bits set. That makes sense because there are no
protection bits in the mask. But, the code certainly doesn't enforce that.
Are you seeing 'sme_me_mask' bits set in 'newprot'?
Yes. AFAIK it's only one bit, and typically always set.
/Thomas
