[Xen-devel] A question about hvm_copy_from_guest_virt

["Li, Xin B" <xin.b.li@xxxxxxxxx>]

current hvm_copy_from_guest_virt implementation can't hanle momery
access crossing a page boundary if the 2 guest physical pages are not
contiguous, but the following code in vmx_io_instruction requires
hvm_copy_from_guest_virt can do that. I remember the original code from
Keir can handle that case, although I don't think there will be a real
case in a OS that the 2 guest physical pages are not contiguous.
The same to movs handling in handle_mmio.
Thanks
-Xin

        /*
         * Handle string pio instructions that cross pages or that
         * are unaligned. See the comments in hvm_domain.c/handle_mmio()
         */
        if ( (addr & PAGE_MASK) != ((addr + size - 1) & PAGE_MASK) ) {
            unsigned long value = 0;

            pio_opp->flags |= OVERLAP;

            if ( dir == IOREQ_WRITE )   /* OUTS */
            {
                if ( hvm_paging_enabled(current) )
                    (void)hvm_copy_from_guest_virt(&value, addr, size);
                else
                    (void)hvm_copy_from_guest_phys(&value, addr, size);
            } else
                pio_opp->addr = addr;

            if ( count == 1 )
                regs->eip += inst_len;

            send_pio_req(port, 1, size, value, dir, df, 0);
        } else {

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