RE: [PATCHv4 3/3] x86/tdx: Handle load_unaligned_zeropad() page-cross to a shared page

[David Laight]

From: Dave Hansen
> Sent: 16 June 2022 00:35
> 
> On 6/15/22 15:52, Kirill A. Shutemov wrote:
> >> +	vaddr = (unsigned long)insn_get_addr_ref(&insn, regs);
> >> +	if (vaddr / PAGE_SIZE != (vaddr + size) / PAGE_SIZE)
> > Oops. I just realized it has off-by-one. It supposed to be:
> >
> > 	if (vaddr / PAGE_SIZE != (vaddr + size - 1) / PAGE_SIZE)
> 
> That was bugging me.  Glad you caught this.
> 
> Wouldn't this be more obviously correct?
> 
> 	if (ALIGN_DOWN(vaddr,        PAGE_SIZE) !=
> 	    ALIGN_DOWN(vaddr + size, PAGE_SIZE))
> 		...
> 
> I don't think we have a PAGE_ALIGN_DOWN().

Or:
	if ((vaddr ^ (vaddr + size - 1)) >> PAGE_SHIFT)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)