Rik van Riel
2005-Jul-12 15:47 UTC
[Xen-devel] Re: [Xen-changelog] This adds a patch for the vanilla kernel, to be pushed upstream some
On Mon, 11 Jul 2005, Xen patchbot -unstable wrote:> --- a/linux-2.6-xen-sparse/arch/xen/i386/mm/pgtable.c Mon Jul 11 15:43:12 2005 > +++ b/linux-2.6-xen-sparse/arch/xen/i386/mm/pgtable.c Mon Jul 11 15:46:46 2005> if (PTRS_PER_PMD == 1 || !pgd) > return pgd; > > + if (!HAVE_SHARED_KERNEL_PMD) { > + /* alloc and copy kernel pmd */ > + unsigned long flags; > + pgd_t *copy_pgd = pgd_offset_k(PAGE_OFFSET); > + pud_t *copy_pud = pud_offset(copy_pgd, PAGE_OFFSET);I don''t understand how the code inside this if condition ever gets to run. Surely the previous test should catch the non-PAE case already ? Or is this code a preparation for non-3:1 splits ? -- The Theory of Escalating Commitment: "The cost of continuing mistakes is borne by others, while the cost of admitting mistakes is borne by yourself." -- Joseph Stiglitz, Nobel Laureate in Economics _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Rik van Riel
2005-Jul-12 16:04 UTC
Re: [Xen-devel] Re: [Xen-changelog] This adds a patch for the vanilla kernel, to be pushed upstream some
On Tue, 12 Jul 2005, Keir Fraser wrote:> On 12 Jul 2005, at 16:47, Rik van Riel wrote: > > > I don''t understand how the code inside this if condition > > ever gets to run. Surely the previous test should catch > > the non-PAE case already ? > > > > Or is this code a preparation for non-3:1 splits ? > > That code path would get executed by native pae builds (ie. non-xen pae > builds).Makes sense. There are non-3:1 splits in native PAE builds. -- The Theory of Escalating Commitment: "The cost of continuing mistakes is borne by others, while the cost of admitting mistakes is borne by yourself." -- Joseph Stiglitz, Nobel Laureate in Economics _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2005-Jul-12 16:07 UTC
Re: [Xen-devel] Re: [Xen-changelog] This adds a patch for the vanilla kernel, to be pushed upstream some
On 12 Jul 2005, at 16:47, Rik van Riel wrote:> I don''t understand how the code inside this if condition > ever gets to run. Surely the previous test should catch > the non-PAE case already ? > > Or is this code a preparation for non-3:1 splits ?That code path would get executed by native pae builds (ie. non-xen pae builds). It''s a dead path on xen/i386 but we keep it around to keep the diff vs i386 small. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Gerd Knorr
2005-Jul-13 07:55 UTC
Re: [Xen-devel] Re: [Xen-changelog] This adds a patch for the vanilla kernel, to be pushed upstream some
Rik van Riel <riel@redhat.com> writes:> On Mon, 11 Jul 2005, Xen patchbot -unstable wrote: > > > --- a/linux-2.6-xen-sparse/arch/xen/i386/mm/pgtable.c Mon Jul 11 15:43:12 2005 > > +++ b/linux-2.6-xen-sparse/arch/xen/i386/mm/pgtable.c Mon Jul 11 15:46:46 2005 > > > if (PTRS_PER_PMD == 1 || !pgd) > > return pgd; > > > > + if (!HAVE_SHARED_KERNEL_PMD) { > > + /* alloc and copy kernel pmd */ > > + unsigned long flags; > > + pgd_t *copy_pgd = pgd_offset_k(PAGE_OFFSET); > > + pud_t *copy_pud = pud_offset(copy_pgd, PAGE_OFFSET); > > I don''t understand how the code inside this if condition > ever gets to run. Surely the previous test should catch > the non-PAE case already ?It''s about PAE mode. xenlinux in PAE mode does _not_ have a shared PMD for the kernel address space. Gerd -- panic("it works"); /* avoid being flooded with debug messages */ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel