3.3-rc1+ loaded MSR_STAR too lazily, breaking workloads
that play with this MSR (or related MSRs) like nested vmx.
Verify that it is loaded eagerly.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
x86/msr.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/x86/msr.c b/x86/msr.c
index c3e0014..307835d 100644
--- a/x86/msr.c
+++ b/x86/msr.c
@@ -2,6 +2,7 @@
#include "libcflat.h"
#include "processor.h"
+#include "msr.h"
struct msr_info {
int index;
@@ -109,6 +110,21 @@ static void test_msr_rw(int msr_index, unsigned long long input, unsigned long l
report(sptr, expected == r);
}
+static void test_syscall_lazy_load(void)
+{
+ extern void syscall_target();
+ u16 cs = read_cs(), ss = read_ss();
+ ulong tmp;
+
+ wrmsr(MSR_EFER, rdmsr(MSR_EFER) | EFER_SCE);
+ wrmsr(MSR_LSTAR, (ulong)syscall_target);
+ wrmsr(MSR_STAR, (uint64_t)cs << 32);
+ asm volatile("pushf; syscall; syscall_target: popf" : "=c"(tmp) : : "r11");
+ write_ss(ss);
+ // will crash horribly if broken
+ report("MSR_*STAR eager loading", true);
+}
+
int main(int ac, char **av)
{
int i, j;
@@ -122,6 +138,8 @@ int main(int ac, char **av)
}
}
+ test_syscall_lazy_load();
+
printf("%d tests, %d failures\n", nr_tests, nr_tests - nr_passed);
return nr_passed == nr_tests ? 0 : 1;
--
1.7.9
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