From bc7a9ccfbd43f3662e63d1a7e9724f2215251e9f Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 2 Mar 2018 12:49:07 -0500
Subject: [PATCH] target-i386: defer VMEXIT to do_interrupt
Paths through the softmmu code during code generation now need to be audited
to check for double locking of tb_lock. In particular, VMEXIT can take tb_lock
through cpu_vmexit -> cpu_x86_update_cr4 -> tlb_flush.
To avoid this, split VMEXIT delivery in two parts, similar to what is done with
exceptions. cpu_vmexit only records the VMEXIT exit code and information, and
cc->do_interrupt can then deliver it when it is safe to take the lock.
Backports commit 10cde894b63146139f981857e4eedf756fa53dcb from qemu
---
qemu/target/i386/cpu.h | 2 ++
qemu/target/i386/seg_helper.c | 20 +++++++++++---------
qemu/target/i386/svm_helper.c | 21 ++++++++++++---------
3 files changed, 25 insertions(+), 18 deletions(-)
diff --git a/qemu/target/i386/cpu.h b/qemu/target/i386/cpu.h
index fa024907..300b49a3 100644
--- a/qemu/target/i386/cpu.h
+++ b/qemu/target/i386/cpu.h
@@ -695,6 +695,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
#define EXCP_SYSCALL 0x100 /* only happens in user only emulation
for syscall instruction */
+#define EXCP_VMEXIT 0x100
/* i386-specific interrupt pending bits. */
#define CPU_INTERRUPT_POLL CPU_INTERRUPT_TGT_EXT_1
@@ -1605,6 +1606,7 @@ void cpu_svm_check_intercept_param(CPUX86State *env1, uint32_t type,
uint64_t param, uintptr_t retaddr);
void cpu_vmexit(CPUX86State *nenv, uint32_t exit_code, uint64_t exit_info_1,
uintptr_t retaddr);
+void do_vmexit(CPUX86State *env, uint32_t exit_code, uint64_t exit_info_1);
/* seg_helper.c */
void do_interrupt_x86_hardirq(CPUX86State *env, int intno, int is_hw);
diff --git a/qemu/target/i386/seg_helper.c b/qemu/target/i386/seg_helper.c
index cb7f8405..934ed219 100644
--- a/qemu/target/i386/seg_helper.c
+++ b/qemu/target/i386/seg_helper.c
@@ -1298,15 +1298,17 @@ void x86_cpu_do_interrupt(CPUState *cs)
/* successfully delivered */
env->old_exception = -1;
#else
- /* simulate a real cpu exception. On i386, it can
- trigger new exceptions, but we do not handle
- double or triple faults yet. */
- do_interrupt_all(cpu, cs->exception_index,
- env->exception_is_int,
- env->error_code,
- env->exception_next_eip, 0);
- /* successfully delivered */
- env->old_exception = -1;
+ if (cs->exception_index >= EXCP_VMEXIT) {
+ assert(env->old_exception == -1);
+ do_vmexit(env, cs->exception_index - EXCP_VMEXIT, env->error_code);
+ } else {
+ do_interrupt_all(cpu, cs->exception_index,
+ env->exception_is_int,
+ env->error_code,
+ env->exception_next_eip, 0);
+ /* successfully delivered */
+ env->old_exception = -1;
+ }
#endif
}
diff --git a/qemu/target/i386/svm_helper.c b/qemu/target/i386/svm_helper.c
index 0c290847..783048e4 100644
--- a/qemu/target/i386/svm_helper.c
+++ b/qemu/target/i386/svm_helper.c
@@ -568,12 +568,10 @@ void helper_svm_check_io(CPUX86State *env, uint32_t port, uint32_t param,
}
}
-/* Note: currently only 32 bits of exit_code are used */
void cpu_vmexit(CPUX86State *env, uint32_t exit_code, uint64_t exit_info_1,
uintptr_t retaddr)
{
CPUState *cs = CPU(x86_env_get_cpu(env));
- uint32_t int_ctl;
if (retaddr) {
cpu_restore_state(cs, retaddr);
@@ -585,6 +583,18 @@ void cpu_vmexit(CPUX86State *env, uint32_t exit_code, uint64_t exit_info_1,
x86_ldq_phys(cs, env->vm_vmcb + offsetof(struct vmcb,
control.exit_info_2)),
env->eip);
+ cs->exception_index = EXCP_VMEXIT + exit_code;
+ env->error_code = exit_info_1;
+
+ /* remove any pending exception */
+ env->old_exception = -1;
+ cpu_loop_exit(cs);
+}
+
+void do_vmexit(CPUX86State *env, uint32_t exit_code, uint64_t exit_info_1)
+{
+ CPUState *cs = CPU(x86_env_get_cpu(env));
+ uint32_t int_ctl;
if (env->hflags & HF_INHIBIT_IRQ_MASK) {
x86_stl_phys(cs,
@@ -747,13 +757,6 @@ void cpu_vmexit(CPUX86State *env, uint32_t exit_code, uint64_t exit_info_1,
/* If the host's rIP reloaded by #VMEXIT is outside the limit of the
host's code segment or non-canonical (in the case of long mode), a
#GP fault is delivered inside the host. */
-
- /* remove any pending exception */
- cs->exception_index = -1;
- env->error_code = 0;
- env->old_exception = -1;
-
- cpu_loop_exit(cs);
}
#endif