Messages in this thread | | | Date | Mon, 21 Jul 2008 21:49:46 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH] x86: fix pte_flags() to only return flags, fix lguest. |
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Rusty Russell wrote: > Change a15af1c9ea2750a9ff01e51615c45950bad8221b 'x86/paravirt: add > pte_flags to just get pte flags' removed lguest's private pte_flags() > in favor of a generic one. > > Unfortunately, the generic one doesn't filter out the non-flags bits: > this results in lguest creating corrupt shadow page tables and blowing > up host memory. > > Since noone is supposed to use the pfn part of pte_flags(), it seems > safest to always do the filtering. >
Thinking about this, I wonder if it needs to be a pv_op at all. Generality says "yes", but there are no users which set it to anything other than native_pte_flags. The point of it is to return the flags as-is, without needing more complex stuff (like Xen's mfn to pfn conversion).
In most cases, the surrounding code will be applying its own mask anyway, so making it a simple inline will allow all the masks to get folded together.
If a user which wants to do something other than return the bare flags, it would be easy enough to put the pv_op back.
> Cc: Jeremy Fitzhardinge <jeremy@goop.org> > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> > > diff -r ee1a6adad3d2 arch/x86/kernel/paravirt.c > --- a/arch/x86/kernel/paravirt.c Mon Jul 21 12:49:25 2008 +1000 > +++ b/arch/x86/kernel/paravirt.c Tue Jul 22 14:09:33 2008 +1000 > @@ -428,7 +428,7 @@ struct pv_mmu_ops pv_mmu_ops = { > #endif /* PAGETABLE_LEVELS >= 3 */ > > .pte_val = native_pte_val, > - .pte_flags = native_pte_val, > + .pte_flags = native_pte_flags, > .pgd_val = native_pgd_val, > > .make_pte = native_make_pte, > diff -r ee1a6adad3d2 include/asm-x86/page.h > --- a/include/asm-x86/page.h Mon Jul 21 12:49:25 2008 +1000 > +++ b/include/asm-x86/page.h Tue Jul 22 14:09:33 2008 +1000 > @@ -144,6 +144,18 @@ static inline pteval_t native_pte_val(pt > return pte.pte; > } > > +/* This belongs in pgtable.h, but our includes are too much of a mess. */ > +#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE) > +#define PTE_FLAGS _AC(0x8000000000000FFF, ULL) > +#else > +#define PTE_FLAGS 0x00000FFF > +#endif > We already have this, it's called PTE_MASK.
J
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