From: Andrew Cooper Date: Fri, 2 Mar 2018 15:41:29 +0000 (+0000) Subject: x86/hvm: Disallow the creation of HVM domains without Local APIC emulation X-Git-Tag: archive/raspbian/4.8.3+comet2+shim4.10.0+comet3-1+deb9u5+rpi1^2~1 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=45c7d2cdc535f8678842cea321b0119a37d82158;p=xen.git x86/hvm: Disallow the creation of HVM domains without Local APIC emulation 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 Reviewed-by: Roger Pau Monné Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Gbp-Pq: Name x86hvm-disallow-the-creation-of-hvm-doma.patch --- diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 8817263ac5..91b9ab75b4 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -557,11 +557,9 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags, return -EINVAL; } - /* PVHv2 guests can request emulated APIC. */ - if ( emflags && - (is_hvm_domain(d) ? ((emflags != XEN_X86_EMU_ALL) && - (emflags != XEN_X86_EMU_LAPIC)) : - (emflags != XEN_X86_EMU_PIT)) ) + if ( is_hvm_domain(d) ? ((emflags != XEN_X86_EMU_ALL) && + (emflags != XEN_X86_EMU_LAPIC)) + : (emflags && emflags != XEN_X86_EMU_PIT) ) { printk(XENLOG_G_ERR "d%d: Xen does not allow %s domain creation " "with the current selection of emulators: %#x\n",