Messages in this thread | | | Date | Tue, 5 May 2015 14:48:34 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH 09/13] KVM: x86: save/load state on SMM switch |
| |
2015-05-05 11:37+0200, Paolo Bonzini: > On 04/05/2015 21:59, Radim Krčmář wrote: > > > The big ugly one. This patch adds support for switching in and out of > > > system management mode, respectively upon receiving KVM_REQ_SMI and upon > > > executing a RSM instruction. Both 32- and 64-bit formats are supported > > > for the SMM state save area. > > > > > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > > > --- > > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > > > +static void rsm_set_desc_flags(struct desc_struct *desc, u16 flags) > > > +{ > > > + desc->g = (flags >> 15) & 1; > > > + desc->d = (flags >> 14) & 1; > > > + desc->l = (flags >> 13) & 1; > > > + desc->avl = (flags >> 12) & 1; > > > + desc->p = (flags >> 7) & 1; > > > + desc->dpl = (flags >> 5) & 3; > > > + desc->s = (flags >> 4) & 1; > > > + desc->type = flags & 15; > > > > I can't find a description of this ... can you point me to a place where > > the gap between 'p' and 'avl' is documented? > > (Not that it matters unless the guest reads it, but it's a bit weird.) > > It turns out that access rights are stored in the same format as the VMX > access rights.
Thanks, so it really has a "reserved" space in the middle, to save some processing because the format is horrible (backward compatible).
> access rights. However, they are shifted by 8, which my code above > doesn't do (bug).
I think you are shifting it right, though ... they wouldn't fit into a word if shifted left.
(I'd just shorten it after finding the right name for mask u32 mask = 0x00f0ff00 desc->b = desc->b & ~mask | flags << 8 & mask
and maybe define 'attributes' field in desc that is already shifted.)
> The documentation is, of course, QEMU and Bochs :) but you can also find > it in http://www.rcollins.org/ftp/source/include/struc.inc. It is not > exactly for SMM, but it is more or less the same.
(It's a register hidden from software, so I have some trust issues :])
| |