From: Masami Hiramatsu mhiramat@kernel.org

commit b3dc0695fa40c3b280230fb6fb7fb7a94ce28bf4 upstream

Gather the emulate prefixes, which forcibly make the following instruction emulated on virtualization, in one place.

Suggested-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Juergen Gross jgross@suse.com Cc: x86@kernel.org Cc: Ingo Molnar mingo@kernel.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Andrew Cooper andrew.cooper3@citrix.com Cc: Stefano Stabellini sstabellini@kernel.org Cc: Borislav Petkov bp@alien8.de Cc: xen-devel@lists.xenproject.org Cc: Randy Dunlap rdunlap@infradead.org Cc: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/156777563917.25081.7286628561790289995.stgit@devno... Signed-off-by: Maximilian Heyne mheyne@amazon.de Cc: stable@vger.kernel.org # 5.4.x --- arch/x86/include/asm/emulate_prefix.h | 14 ++++++++++++++ arch/x86/include/asm/xen/interface.h | 11 ++++------- arch/x86/kvm/x86.c | 4 +++- 3 files changed, 21 insertions(+), 8 deletions(-) create mode 100644 arch/x86/include/asm/emulate_prefix.h

diff --git a/arch/x86/include/asm/emulate_prefix.h b/arch/x86/include/asm/emulate_prefix.h new file mode 100644 index 000000000000..70f5b98a5286 --- /dev/null +++ b/arch/x86/include/asm/emulate_prefix.h @@ -0,0 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_EMULATE_PREFIX_H +#define _ASM_X86_EMULATE_PREFIX_H + +/* + * Virt escape sequences to trigger instruction emulation; + * ideally these would decode to 'whole' instruction and not destroy + * the instruction stream; sadly this is not true for the 'kvm' one :/ + */ + +#define __XEN_EMULATE_PREFIX 0x0f,0x0b,0x78,0x65,0x6e /* ud2 ; .ascii "xen" */ +#define __KVM_EMULATE_PREFIX 0x0f,0x0b,0x6b,0x76,0x6d /* ud2 ; .ascii "kvm" */ + +#endif diff --git a/arch/x86/include/asm/xen/interface.h b/arch/x86/include/asm/xen/interface.h index 62ca03ef5c65..9139b3e86316 100644 --- a/arch/x86/include/asm/xen/interface.h +++ b/arch/x86/include/asm/xen/interface.h @@ -379,12 +379,9 @@ struct xen_pmu_arch { * Prefix forces emulation of some non-trapping instructions. * Currently only CPUID. */ -#ifdef __ASSEMBLY__ -#define XEN_EMULATE_PREFIX .byte 0x0f,0x0b,0x78,0x65,0x6e ; -#define XEN_CPUID XEN_EMULATE_PREFIX cpuid -#else -#define XEN_EMULATE_PREFIX ".byte 0x0f,0x0b,0x78,0x65,0x6e ; " -#define XEN_CPUID XEN_EMULATE_PREFIX "cpuid" -#endif +#include <asm/emulate_prefix.h> + +#define XEN_EMULATE_PREFIX __ASM_FORM(.byte __XEN_EMULATE_PREFIX ;) +#define XEN_CPUID XEN_EMULATE_PREFIX __ASM_FORM(cpuid)

#endif /* _ASM_X86_XEN_INTERFACE_H */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1f7dfa5aa42d..6dd77e426889 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -68,6 +68,7 @@ #include <asm/mshyperv.h> #include <asm/hypervisor.h> #include <asm/intel_pt.h> +#include <asm/emulate_prefix.h> #include <clocksource/hyperv_timer.h>

#define CREATE_TRACE_POINTS @@ -5583,6 +5584,7 @@ EXPORT_SYMBOL_GPL(kvm_write_guest_virt_system);

int handle_ud(struct kvm_vcpu *vcpu) { + static const char kvm_emulate_prefix[] = { __KVM_EMULATE_PREFIX }; int emul_type = EMULTYPE_TRAP_UD; char sig[5]; /* ud2; .ascii "kvm" */ struct x86_exception e; @@ -5590,7 +5592,7 @@ int handle_ud(struct kvm_vcpu *vcpu) if (force_emulation_prefix && kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e) == 0 && - memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) { + memcmp(sig, kvm_emulate_prefix, sizeof(sig)) == 0) { kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig)); emul_type = EMULTYPE_TRAP_UD_FORCED; }