| Message ID | 1476439616-17287-1-git-send-email-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
>>> On 14.10.16 at 12:06, <andrew.cooper3@citrix.com> wrote: > Contrary to the description in the software manuals, in Long Mode, attempts to > load %cs check that D is not set in combination with L before the present flag > is checked. > > This can be observed because the L/D check fails with #GP before the presence > check failes with #NP > > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> But I think it would be worthwhile mentioning that this restores things to v1 of what became commit 78ff18c90. Jan
On 14/10/16 11:28, Jan Beulich wrote: >>>> On 14.10.16 at 12:06, <andrew.cooper3@citrix.com> wrote: >> Contrary to the description in the software manuals, in Long Mode, attempts to >> load %cs check that D is not set in combination with L before the present flag >> is checked. >> >> This can be observed because the L/D check fails with #GP before the presence >> check failes with #NP >> >> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > Reviewed-by: Jan Beulich <jbeulich@suse.com> > > But I think it would be worthwhile mentioning that this restores > things to v1 of what became commit 78ff18c90. I will update the comment to include this. ~Andrew
On Fri, Oct 14, 2016 at 11:06:55AM +0100, Andrew Cooper wrote: > Contrary to the description in the software manuals, in Long Mode, attempts to > load %cs check that D is not set in combination with L before the present flag > is checked. > > This can be observed because the L/D check fails with #GP before the presence > check failes with #NP CC-ing Paul and Sherry. Perhaps the SDMs should mention this as well? > > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> > --- > CC: Jan Beulich <JBeulich@suse.com> > --- > xen/arch/x86/x86_emulate/x86_emulate.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c > index 793ce30..b23cd99 100644 > --- a/xen/arch/x86/x86_emulate/x86_emulate.c > +++ b/xen/arch/x86/x86_emulate/x86_emulate.c > @@ -1405,6 +1405,14 @@ protmode_load_seg( > /* Non-conforming segment: check RPL and DPL against CPL. */ > : rpl > cpl || dpl != cpl ) > goto raise_exn; > + /* > + * 64-bit code segments (L bit set) must have D bit clear. > + * Experimentally in long mode, the L and D bits are checked before > + * the Present bit. > + */ > + if ( in_longmode(ctxt, ops) && > + (desc.b & (1 << 21)) && (desc.b & (1 << 22)) ) > + goto raise_exn; > sel = (sel ^ rpl) | cpl; > break; > case x86_seg_ss: > @@ -1444,11 +1452,6 @@ protmode_load_seg( > goto raise_exn; > } > > - /* 64-bit code segments (L bit set) must have D bit clear. */ > - if ( seg == x86_seg_cs && in_longmode(ctxt, ops) && > - (desc.b & (1 << 21)) && (desc.b & (1 << 22)) ) > - goto raise_exn; > - > /* Ensure Accessed flag is set. */ > if ( a_flag && !(desc.b & a_flag) ) > { > -- > 2.1.4 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > https://lists.xen.org/xen-devel
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 793ce30..b23cd99 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -1405,6 +1405,14 @@ protmode_load_seg( /* Non-conforming segment: check RPL and DPL against CPL. */ : rpl > cpl || dpl != cpl ) goto raise_exn; + /* + * 64-bit code segments (L bit set) must have D bit clear. + * Experimentally in long mode, the L and D bits are checked before + * the Present bit. + */ + if ( in_longmode(ctxt, ops) && + (desc.b & (1 << 21)) && (desc.b & (1 << 22)) ) + goto raise_exn; sel = (sel ^ rpl) | cpl; break; case x86_seg_ss: @@ -1444,11 +1452,6 @@ protmode_load_seg( goto raise_exn; } - /* 64-bit code segments (L bit set) must have D bit clear. */ - if ( seg == x86_seg_cs && in_longmode(ctxt, ops) && - (desc.b & (1 << 21)) && (desc.b & (1 << 22)) ) - goto raise_exn; - /* Ensure Accessed flag is set. */ if ( a_flag && !(desc.b & a_flag) ) {
Contrary to the description in the software manuals, in Long Mode, attempts to load %cs check that D is not set in combination with L before the present flag is checked. This can be observed because the L/D check fails with #GP before the presence check failes with #NP Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> --- xen/arch/x86/x86_emulate/x86_emulate.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)