KVM: SVM: Use asm goto to handle unexpected #UD on SVM instructions

Add svm_asm*() macros, a la the existing vmx_asm*() macros, to handle
faults on SVM instructions instead of using the generic __ex(), a.k.a.
__kvm_handle_fault_on_reboot().  Using asm goto generates slightly
better code as it eliminates the in-line JMP+CALL sequences that are
needed by __kvm_handle_fault_on_reboot() to avoid triggering BUG()
from fixup (which generates bad stack traces).

Using SVM specific macros also drops the last user of __ex() and the
the last asm linkage to kvm_spurious_fault(), and adds a helper for
VMSAVE, which may gain an addition call site in the future (as part
of optimizing the SVM context switching).

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201231002702.2223707-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/svm_ops.h b/arch/x86/kvm/svm/svm_ops.h
new file mode 100644
index 000000000000..9f007bc8409a
--- /dev/null
+++ b/arch/x86/kvm/svm/svm_ops.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __KVM_X86_SVM_OPS_H
+#define __KVM_X86_SVM_OPS_H
+
+#include <linux/compiler_types.h>
+
+#include <asm/kvm_host.h>
+
+#define svm_asm(insn, clobber...)				\
+do {								\
+	asm_volatile_goto("1: " __stringify(insn) "\n\t"	\
+			  _ASM_EXTABLE(1b, %l[fault])		\
+			  ::: clobber : fault);			\
+	return;							\
+fault:								\
+	kvm_spurious_fault();					\
+} while (0)
+
+#define svm_asm1(insn, op1, clobber...)				\
+do {								\
+	asm_volatile_goto("1: "  __stringify(insn) " %0\n\t"	\
+			  _ASM_EXTABLE(1b, %l[fault])		\
+			  :: op1 : clobber : fault);		\
+	return;							\
+fault:								\
+	kvm_spurious_fault();					\
+} while (0)
+
+#define svm_asm2(insn, op1, op2, clobber...)				\
+do {									\
+	asm_volatile_goto("1: "  __stringify(insn) " %1, %0\n\t"	\
+			  _ASM_EXTABLE(1b, %l[fault])			\
+			  :: op1, op2 : clobber : fault);		\
+	return;								\
+fault:									\
+	kvm_spurious_fault();						\
+} while (0)
+
+static inline void clgi(void)
+{
+	svm_asm(clgi);
+}
+
+static inline void stgi(void)
+{
+	svm_asm(stgi);
+}
+
+static inline void invlpga(unsigned long addr, u32 asid)
+{
+	svm_asm2(invlpga, "c"(asid), "a"(addr));
+}
+
+/*
+ * Despite being a physical address, the portion of rAX that is consumed by
+ * VMSAVE, VMLOAD, etc... is still controlled by the effective address size,
+ * hence 'unsigned long' instead of 'hpa_t'.
+ */
+static inline void vmsave(unsigned long pa)
+{
+	svm_asm1(vmsave, "a" (pa), "memory");
+}
+
+#endif /* __KVM_X86_SVM_OPS_H */