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diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S
--- a/sys/amd64/amd64/exception.S
+++ b/sys/amd64/amd64/exception.S
@@ -667,9 +667,10 @@
jnz dbg_fromuserspace
lfence
/*
- * We've interrupted the kernel. Preserve GS.base in %r12,
- * %cr3 in %r13, and possibly lower half of MSR_IA32_SPEC_CTL in %r14d.
+ * We've interrupted the kernel. See comment in NMI handler about
+ * registers use.
*/
+ movq %cr2,%r15
movl $MSR_GSBASE,%ecx
rdmsr
movq %rax,%r12
@@ -710,6 +711,7 @@
shrq $32,%rdx
wrmsr
movq %r13,%cr3
+ movq %r15,%cr2
RESTORE_REGS
addq $TF_RIP,%rsp
jmp doreti_iret
@@ -804,10 +806,14 @@
testb $SEL_RPL_MASK,TF_CS(%rsp)
jnz nmi_fromuserspace
/*
- * We've interrupted the kernel. Preserve GS.base in %r12,
- * %cr3 in %r13, and possibly lower half of MSR_IA32_SPEC_CTL in %r14d.
+ * We've interrupted the kernel. Preserve in callee-saved regs:
+ * GS.base in %r12,
+ * %cr3 in %r13,
+ * possibly lower half of MSR_IA32_SPEC_CTL in %r14d,
+ * %cr2 in %r15.
*/
lfence
+ movq %cr2,%r15
movl $MSR_GSBASE,%ecx
rdmsr
movq %rax,%r12
@@ -957,6 +963,7 @@
je 2f
call flush_l1d_sw /* bhyve L1TF assist */
2: movq %r13,%cr3
+ movq %r15,%cr2
RESTORE_REGS
addq $TF_RIP,%rsp
jmp doreti_iret
@@ -1011,9 +1018,10 @@
testb $SEL_RPL_MASK,TF_CS(%rsp)
jnz mchk_fromuserspace
/*
- * We've interrupted the kernel. Preserve GS.base in %r12,
- * %cr3 in %r13, and possibly lower half of MSR_IA32_SPEC_CTL in %r14d.
+ * We've interrupted the kernel. See comment in NMI handler about
+ * registers use.
*/
+ movq %cr2,%r15
movl $MSR_GSBASE,%ecx
rdmsr
movq %rax,%r12
@@ -1071,6 +1079,7 @@
shrq $32,%rdx
wrmsr
movq %r13,%cr3
+ movq %r15,%cr2
RESTORE_REGS
addq $TF_RIP,%rsp
jmp doreti_iret
diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S
--- a/sys/amd64/amd64/support.S
+++ b/sys/amd64/amd64/support.S
@@ -1651,7 +1651,8 @@
*
* N.B. The function does not follow ABI calling conventions, it corrupts %rbx.
* The vmm.ko caller expects that only %rax, %rdx, %rbx, %rcx, %r9, and %rflags
- * registers are clobbered. The NMI handler caller only needs %r13 preserved.
+ * registers are clobbered. The NMI handler caller only needs %r13 and %r15
+ * preserved.
*/
ENTRY(flush_l1d_sw)
#define L1D_FLUSH_SIZE (64 * 1024)

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