On Wed, Jun 13, 2018 at 06:13:03PM +0000, Dave Hansen wrote: > On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: > > Encrypted VMA will have KeyID stored in vma->vm_page_prot. This way we > > "An encrypted VMA..." > > > don't need to do anything special to setup encrypted page table entries > > and don't need to reserve space for KeyID in a VMA. > > > > This patch changes _PAGE_CHG_MASK to include KeyID bits. Otherwise they > > are going to be stripped from vm_page_prot on the first pgprot_modify(). > > > > Define PTE_PFN_MASK_MAX similar to PTE_PFN_MASK but based on > > __PHYSICAL_MASK_SHIFT. This way we include whole range of bits > > architecturally available for PFN without referencing physical_mask and > > mktme_keyid_mask variables. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > --- > > arch/x86/include/asm/pgtable_types.h | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h > > index 1e5a40673953..e8ebe760b88d 100644 > > --- a/arch/x86/include/asm/pgtable_types.h > > +++ b/arch/x86/include/asm/pgtable_types.h > > @@ -121,8 +121,13 @@ > > * protection key is treated like _PAGE_RW, for > > * instance, and is *not* included in this mask since > > * pte_modify() does modify it. > > + * > > + * It includes full range of PFN bits regardless if they were claimed for KeyID > > + * or not: we want to preserve KeyID on pte_modify() and pgprot_modify(). > > */ > > -#define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT | \ > > +#define PTE_PFN_MASK_MAX \ > > + (((signed long)PAGE_MASK) & ((1ULL << __PHYSICAL_MASK_SHIFT) - 1)) > > "signed long" is really unusual to see. Was that intentional? Yes. That's trick with sign-extension, borrowed from PHYSICAL_PAGE_MASK definition. It helps on 32-bit with PAE properly expand the PAGE_MASK to 64-bit. I'll add comment. > > +#define _PAGE_CHG_MASK (PTE_PFN_MASK_MAX | _PAGE_PCD | _PAGE_PWT | \ > > _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY | \ > > _PAGE_SOFT_DIRTY) > > #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE) > > This makes me a bit nervous. We have some places (here) where we > pretend that the KeyID is part of the paddr and then other places like > pte_pfn() where it's not. Other option is to include KeyID mask into _PAGE_CHG_MASK. But it means _PAGE_CHG_MASK would need to reference *two* variables: physical_mask and mktme_keyid_mask. I mentioned this in the commit message. This is more efficient way to achieve the same compile-time without referencing any variables. > Seems like something that will come back to bite us. Any suggestions? -- Kirill A. Shutemov
