Re: [PATCH] tools/libxc: Correct XC_DOM_PAGE_SIZE() to return a long long

[Wei Liu <wei.liu2@citrix.com>]

On Thu, Nov 19, 2015 at 05:01:52PM +0000, Andrew Cooper wrote:
> On 19/11/15 16:50, Wei Liu wrote:
> > On Thu, Nov 19, 2015 at 02:45:41PM +0000, Andrew Cooper wrote:
> >> c/s abdf3c5b "libxc: create p2m list outside of kernel mapping if supported"
> >> introduces a use which Coverity objects to; an int used to mask a uint64_t.
> >>
> >> The result needs to be signed to allow ~XC_DOM_PAGE_SIZE() to function
> > $ git grep XC_DOM_PAGE_SIZE
> >
> > tools/libxc/include/xc_dom.h:#define XC_DOM_PAGE_SIZE(dom)   (1 << (dom)->arch_hooks
> > tools/libxc/include/xc_dom.h:    unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:    unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:    unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:    unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:    unsigned int page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:    page_size = XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_core.c:         (dom->parms.p2m_base & (XC_DOM_PAGE_SIZE(dom) - 1
> > tools/libxc/xc_dom_elfloader.c:    elf->dest_size = pages * XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_hvmloader.c:    elf->dest_size = pages * XC_DOM_PAGE_SIZE(dom);
> > tools/libxc/xc_dom_x86.c:    memset(l3tab, 0, XC_DOM_PAGE_SIZE(dom));
> >
> > There is no use for ~XC_DOM_PAGE_SIZE.
> >
> > And what is the possible scenario you want that?
> 
> There might not be a current user of this in libxc, but it is a common bug.
> 
> From xen/include/asm-x86/page.h
> 
> /*                                                                                                                                                                                      
> 
>  * It is important that the masks are signed quantities. This ensures
> that                                                                                                              
> 
>  * the compiler sign-extends a 32-bit mask to 64 bits if that is
> required.                                                                                                              
> 
>  */
> #define PAGE_SIZE           (_AC(1,L) << PAGE_SHIFT)
> #define PAGE_MASK           (~(PAGE_SIZE-1))
> #define PAGE_FLAG_MASK      (~0)
> 
> #define PAGE_ORDER_4K       0
> #define PAGE_ORDER_2M       9
> #define PAGE_ORDER_1G       18
> 


Good to know.

Acked-by: Wei Liu <wei.liu2@citrix.com>

> ~Andrew