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x86: xen: kvm: Gather the definition of emulate prefixes 

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@devnote2
This commit is contained in:
Masami Hiramatsu 2019-09-06 22:13:59 +09:00 committed by Peter Zijlstra
parent f7919fd943
commit b3dc0695fa
3 changed files with 21 additions and 8 deletions
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14
arch/x86/include/asm/emulate_prefix.h Normal file
View File

@ -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

11
arch/x86/include/asm/xen/interface.h
View File

@ -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 */

4
arch/x86/kvm/x86.c
View File

@ -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
@ -5446,6 +5447,7 @@ 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;
@ -5453,7 +5455,7 @@ 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;
}