From 0aa6158b674c5d083b75ac8fcd1e7ae92d0c39ae Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Tue, 27 Feb 2018 14:08:36 +0100 Subject: [PATCH] x86/hvm: Disallow the creation of HVM domains without Local APIC emulation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit There are multiple problems, not necesserily limited to: * Guests which configure event channels via hvmop_set_evtchn_upcall_vector(), or which hit %cr8 emulation will cause Xen to fall over a NULL vlapic->regs pointer. * On Intel hardware, disabling the TPR_SHADOW execution control without reenabling CR8_{LOAD,STORE} interception means that the guests %cr8 accesses interact with the real TPR. Amongst other things, setting the real TPR to 0xf blocks even IPIs from interrupting this CPU. * On hardware which sets up the use of Interrupt Posting, including IOMMU-Posting, guests run without the appropriate non-root configuration, which at a minimum will result in dropped interrupts. Whether no-LAPIC mode is of any use at all remains to be seen. This is XSA-256. Reported-by: Ian Jackson Signed-off-by: Andrew Cooper Reviewed-by: Roger Pau Monné Reviewed-by: Jan Beulich --- xen/arch/x86/domain.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 9c3527f077..1f8b08ef02 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -413,7 +413,7 @@ static bool emulation_flags_ok(const struct domain *d, uint32_t emflags) if ( is_hardware_domain(d) && emflags != (XEN_X86_EMU_LAPIC|XEN_X86_EMU_IOAPIC) ) return false; - if ( !is_hardware_domain(d) && emflags && + if ( !is_hardware_domain(d) && emflags != XEN_X86_EMU_ALL && emflags != XEN_X86_EMU_LAPIC ) return false; } -- 2.30.2