On Tue, Sep 10, 2013 at 01:05:21PM +0200, Paolo Bonzini wrote:
> Il 04/09/2013 18:44, Paul Gortmaker ha scritto:
> > Hi Greg,
> > 
> > The 3.4.44+ cherry pick:
> > 
> >   ----------------
> >   commit 5b5b30580218eae22609989546bac6e44d0eda6e
> >   Author: Gleb Natapov <[email protected]>
> >   Date:   Wed Apr 24 13:38:36 2013 +0300
> > 
> >     KVM: X86 emulator: fix source operand decoding for 8bit mov[zs]x 
> > instructions
> >     
> >     commit 660696d1d16a71e15549ce1bf74953be1592bcd3 upstream.
> >     
> >     Source operand for one byte mov[zs]x is decoded incorrectly if it is in
> >     high byte register. Fix that.
> >     
> >     Signed-off-by: Gleb Natapov <[email protected]>
> >     Signed-off-by: Greg Kroah-Hartman <[email protected]>
> >   ----------------
> > 
> > introduces the following:
> > 
> > arch/x86/kvm/emulate.c: In function ‘decode_operand’:
> > arch/x86/kvm/emulate.c:3974:4: warning: passing argument 1 of 
> > ‘decode_register’ makes integer from pointer without a cast [enabled by 
> > default]
> > arch/x86/kvm/emulate.c:789:14: note: expected ‘u8’ but argument is of type 
> > ‘struct x86_emulate_ctxt *’
> > arch/x86/kvm/emulate.c:3974:4: warning: passing argument 2 of 
> > ‘decode_register’ makes pointer from integer without a cast [enabled by 
> > default]
> > arch/x86/kvm/emulate.c:789:14: note: expected ‘long unsigned int *’ but 
> > argument is of type ‘u8’
> > 
> > Based on the severity of the warnings above, I'm reasonably sure there will
> > be some kind of runtime regressions due to this, but I stopped to 
> > investigate
> > the warnings as soon as I saw them, before any run time testing.
> > 
> > It happens because mainline v3.7-rc1~113^2~40 (dd856efafe60) does this:
> > 
> > -static void *decode_register(u8 modrm_reg, unsigned long *regs,
> > +static void *decode_register(struct x86_emulate_ctxt *ctxt, u8 modrm_reg,
> > 
> > Since 660696d1d16a71e1 was only applied to stable 3.4, 3.8, and 3.9 -- and
> > the prerequisite above is in 3.7+, the issue should be limited to 3.4.44+
> 
> Right, the fix is not important to have for 3.4 kernels.

Thanks for letting me know, I've now reverted it.

greg k-h
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