Re: [Xen-devel] [PATCH for-next] xen/pv: Construct d0v0's GDT properly
On 16/10/17 16:58, Jan Beulich wrote: On 16.10.17 at 16:38,wrote: >> c/s cf6d39f8199 "x86/PV: properly populate descriptor tables" changed the GDT >> to reference zero_page for intermediate frames between the guest and Xen >> frames. >> >> Because dom0_construct_pv() doesn't call arch_set_info_guest(), some bits of >> initialisation are missed, including the pv_destroy_gdt() which initially >> fills the references to zero_page. >> >> In practice, this means there is a window between starting and the first call >> to HYPERCALL_set_gdt() were lar/lsl/verr/verw suffer non-architectural >> behaviour. >> >> Signed-off-by: Andrew Cooper > Reviewed-by: Jan Beulich > >> This probably wants backporting to Xen 4.7 and later. > Could you remind me once the patch has gone in (as that'll be only > in quite a few weeks)? I will stick this in my x86-next branch, and leave myself a note. (I guess we will see how well this scheme works.) ~Andrew ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH for-next] xen/pv: Construct d0v0's GDT properly
>>> On 16.10.17 at 16:38,wrote: > c/s cf6d39f8199 "x86/PV: properly populate descriptor tables" changed the GDT > to reference zero_page for intermediate frames between the guest and Xen > frames. > > Because dom0_construct_pv() doesn't call arch_set_info_guest(), some bits of > initialisation are missed, including the pv_destroy_gdt() which initially > fills the references to zero_page. > > In practice, this means there is a window between starting and the first call > to HYPERCALL_set_gdt() were lar/lsl/verr/verw suffer non-architectural > behaviour. > > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich > This probably wants backporting to Xen 4.7 and later. Could you remind me once the patch has gone in (as that'll be only in quite a few weeks)? Thanks, Jan ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
[Xen-devel] [PATCH for-next] xen/pv: Construct d0v0's GDT properly
c/s cf6d39f8199 "x86/PV: properly populate descriptor tables" changed the GDT to reference zero_page for intermediate frames between the guest and Xen frames. Because dom0_construct_pv() doesn't call arch_set_info_guest(), some bits of initialisation are missed, including the pv_destroy_gdt() which initially fills the references to zero_page. In practice, this means there is a window between starting and the first call to HYPERCALL_set_gdt() were lar/lsl/verr/verw suffer non-architectural behaviour. Signed-off-by: Andrew Cooper--- CC: Jan Beulich This probably wants backporting to Xen 4.7 and later. --- xen/arch/x86/pv/dom0_build.c | 8 1 file changed, 8 insertions(+) diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c index 8ad7e3d..984a94a 100644 --- a/xen/arch/x86/pv/dom0_build.c +++ b/xen/arch/x86/pv/dom0_build.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include "mm.h" @@ -867,6 +868,13 @@ int __init dom0_construct_pv(struct domain *d, regs->rsi = vstartinfo_start; regs->eflags = X86_EFLAGS_IF; +/* + * We don't call arch_set_info_guest(), so some initialisation needs doing + * by hand: + * - Reset the GDT to reference zero_page + */ +pv_destroy_gdt(v); + if ( test_bit(XENFEAT_supervisor_mode_kernel, parms.f_required) ) panic("Dom0 requires supervisor-mode execution"); -- 2.1.4 ___ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel