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41 lines
1.7 KiB
Diff
41 lines
1.7 KiB
Diff
From: Andrew Cooper <andrew.cooper3@citrix.com>
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Subject: x86/hvm: Disallow the creation of HVM domains without Local APIC emulation
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There are multiple problems, not necesserily limited to:
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* Guests which configure event channels via hvmop_set_evtchn_upcall_vector(),
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or which hit %cr8 emulation will cause Xen to fall over a NULL vlapic->regs
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pointer.
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* On Intel hardware, disabling the TPR_SHADOW execution control without
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reenabling CR8_{LOAD,STORE} interception means that the guests %cr8
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accesses interact with the real TPR. Amongst other things, setting the
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real TPR to 0xf blocks even IPIs from interrupting this CPU.
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* On hardware which sets up the use of Interrupt Posting, including
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IOMMU-Posting, guests run without the appropriate non-root configuration,
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which at a minimum will result in dropped interrupts.
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Whether no-LAPIC mode is of any use at all remains to be seen.
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This is XSA-256.
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Reported-by: Ian Jackson <ian.jackson@eu.citrix.com>
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Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
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Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Reviewed-by: Jan Beulich <jbeulich@suse.com>
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diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
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index f93327b..f65fc12 100644
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--- a/xen/arch/x86/domain.c
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+++ b/xen/arch/x86/domain.c
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@@ -413,7 +413,7 @@ static bool emulation_flags_ok(const struct domain *d, uint32_t emflags)
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if ( is_hardware_domain(d) &&
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emflags != (XEN_X86_EMU_LAPIC|XEN_X86_EMU_IOAPIC) )
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return false;
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- if ( !is_hardware_domain(d) && emflags &&
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+ if ( !is_hardware_domain(d) &&
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emflags != XEN_X86_EMU_ALL && emflags != XEN_X86_EMU_LAPIC )
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return false;
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}
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