For a while now, we are issuing a rdmsr instruction to find out which msrs in our
save list are really supported by the underlying machine. However, it fails to account
for kvm-specific msrs, such as the pvclock ones.
This patch moves then to the beginning of the list, and skip testing them.
Signed-off-by: Glauber Costa <[email protected]>
---
arch/x86/kvm/x86.c | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 11a6f2f..747e566 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -503,16 +503,19 @@ static inline u32 bit(int bitno)
* and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.
*
* This list is modified at module load time to reflect the
- * capabilities of the host cpu.
+ * capabilities of the host cpu. This capabilities test skips MSRs that are
+ * kvm-specific. Those are put in the beginning of the list.
*/
+
+#define KVM_SAVE_MSRS_BEGIN 2
static u32 msrs_to_save[] = {
+ MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
MSR_K6_STAR,
#ifdef CONFIG_X86_64
MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
#endif
- MSR_IA32_TSC, MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
- MSR_IA32_PERF_STATUS, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
+ MSR_IA32_TSC, MSR_IA32_PERF_STATUS, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
};
static unsigned num_msrs_to_save;
@@ -2446,7 +2449,8 @@ static void kvm_init_msr_list(void)
u32 dummy[2];
unsigned i, j;
- for (i = j = 0; i < ARRAY_SIZE(msrs_to_save); i++) {
+ /* skip the first msrs in the list. KVM-specific */
+ for (i = j = KVM_SAVE_MSRS_BEGIN; i < ARRAY_SIZE(msrs_to_save); i++) {
if (rdmsr_safe(msrs_to_save[i], &dummy[0], &dummy[1]) < 0)
continue;
if (j < i)
--
1.6.2.2
On Tue, Oct 06, 2009 at 01:24:50PM -0400, Glauber Costa wrote:
> For a while now, we are issuing a rdmsr instruction to find out which msrs in our
> save list are really supported by the underlying machine. However, it fails to account
> for kvm-specific msrs, such as the pvclock ones.
>
> This patch moves then to the beginning of the list, and skip testing them.
>
> Signed-off-by: Glauber Costa <[email protected]>
Applied, thanks.
But this alone won't fix migration to include the two pvclock MSRs
right?
On Mon, Oct 12, 2009 at 02:50:27PM -0300, Marcelo Tosatti wrote:
> On Tue, Oct 06, 2009 at 01:24:50PM -0400, Glauber Costa wrote:
> > For a while now, we are issuing a rdmsr instruction to find out which msrs in our
> > save list are really supported by the underlying machine. However, it fails to account
> > for kvm-specific msrs, such as the pvclock ones.
> >
> > This patch moves then to the beginning of the list, and skip testing them.
> >
> > Signed-off-by: Glauber Costa <[email protected]>
>
> Applied, thanks.
>
> But this alone won't fix migration to include the two pvclock MSRs
> right?
Yes, exactly. It will just make userspace see the correct list, but we'd
still have to take action based on it.