Andre Przywara wrote:
sysenter/sysexit are not supported on AMD's 32bit compat mode, whereas
syscall is not supported on Intel's 32bit compat mode. To allow cross
vendor migration we emulate the missing instructions by setting up the
processor state according to the other call.
The sysenter code was originally sketched by Amit Shah, it was completed,
debugged, syscall added and made-to-work by Christoph Egger and polished
up by Andre Przywara.
Please note that sysret does not need to be emulated, because it will be
exectued in 64bit mode and returning to 32bit compat mode works on Intel.
++vcpu->stat.insn_emulation;
if (r) {
diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 22c765d..41b78fa 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -32,6 +32,8 @@
#include <linux/module.h>
#include <asm/kvm_x86_emulate.h>
+#include "mmu.h"
+
I think this is unneeded?
@@ -1985,10 +1992,114 @@ twobyte_insn:
goto cannot_emulate;
}
break;
+ case 0x05: { /* syscall */
+ unsigned long cr0 = ctxt->vcpu->arch.cr0;
+ struct kvm_segment cs, ss;
+
+ memset(&cs, 0, sizeof(struct kvm_segment));
+ memset(&ss, 0, sizeof(struct kvm_segment));
+
+ /* inject #UD if
+ * 1. we are in real mode
+ * 2. protected mode is not enabled
+ * 3. LOCK prefix is used
+ */
+ if ((ctxt->mode == X86EMUL_MODE_REAL)
+ || (!(cr0 & X86_CR0_PE))
+ || (c->lock_prefix)) {
+ /* we don't need to inject #UD here, because
+ * when emulate_instruction() returns something else
+ * than EMULATE_DONE, then svm.c:ud_interception()
+ * will do that for us.
+ */
+ goto cannot_emulate;
I prefer explicit injection, relying on the caller is tricky and may change.
+ case 0x07: /* sysret */
Since we don't emulate sysret, it should be dropped here.
+ cs.limit = 0xffffffff;
+ ss.base = 0;
+ ss.limit = 0xffffffff;
Once is enough.
Please move the code out of the switch and into separate functions.
--
error compiling committee.c: too many arguments to function
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