On Sun, Jul 7, 2013 at 4:50 PM, Gleb Natapov <g...@redhat.com> wrote:
> On Sun, Jul 07, 2013 at 04:47:05PM +0800, Arthur Chunqi Li wrote:
>> On Sun, Jul 7, 2013 at 3:20 PM, Gleb Natapov <g...@redhat.com> wrote:
>> > On Sun, Jul 07, 2013 at 03:16:08PM +0800, Arthur Chunqi Li wrote:
>> >> On Sun, Jul 7, 2013 at 2:59 PM, Gleb Natapov <g...@redhat.com> wrote:
>> >> > On Fri, Jul 05, 2013 at 11:13:17PM +0800, Arthur Chunqi Li wrote:
>> >> >> Fix read/write to IA32_FEATURE_CONTROL MSR in nested environment.
>> >> >>
>> >> >> This patch simulate this MSR in nested_vmx and the default value is
>> >> >> 0x0. BIOS should set it to 0x5 before VMXON. After setting the lock
>> >> >> bit, write to it will cause #GP(0).
>> >> >>
>> >> >> Signed-off-by: Arthur Chunqi Li <yzt...@gmail.com>
>> >> > The patch is heavily based on Nadav's one. You need to preserve
>> >> > authorship. Add From: and Nadav's Sign-off-by.
>> >> >
>> >> >> ---
>> >> >> arch/x86/kvm/vmx.c | 25 +++++++++++++++++++++----
>> >> >> arch/x86/kvm/x86.c | 3 ++-
>> >> >> 2 files changed, 23 insertions(+), 5 deletions(-)
>> >> >>
>> >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> >> >> index 260a919..5e3d44e 100644
>> >> >> --- a/arch/x86/kvm/vmx.c
>> >> >> +++ b/arch/x86/kvm/vmx.c
>> >> >> @@ -373,6 +373,7 @@ struct nested_vmx {
>> >> >> * we must keep them pinned while L2 runs.
>> >> >> */
>> >> >> struct page *apic_access_page;
>> >> >> + u64 msr_ia32_feature_control;
>> >> >> };
>> >> >>
>> >> >> #define POSTED_INTR_ON 0
>> >> >> @@ -2277,8 +2278,11 @@ static int vmx_get_vmx_msr(struct kvm_vcpu
>> >> >> *vcpu, u32 msr_index, u64 *pdata)
>> >> >>
>> >> >> switch (msr_index) {
>> >> >> case MSR_IA32_FEATURE_CONTROL:
>> >> >> - *pdata = 0;
>> >> >> - break;
>> >> >> + if (nested_vmx_allowed(vcpu)){
>> >> >> + *pdata =
>> >> >> to_vmx(vcpu)->nested.msr_ia32_feature_control;
>> >> >> + break;
>> >> >> + }
>> >> >> + return 0;
>> >> >> case MSR_IA32_VMX_BASIC:
>> >> >> /*
>> >> >> * This MSR reports some information about VMX support.
>> >> >> We
>> >> >> @@ -2356,9 +2360,13 @@ static int vmx_set_vmx_msr(struct kvm_vcpu
>> >> >> *vcpu, u32 msr_index, u64 data)
>> >> >> if (!nested_vmx_allowed(vcpu))
>> >> >> return 0;
>> >> >>
>> >> >> - if (msr_index == MSR_IA32_FEATURE_CONTROL)
>> >> >> - /* TODO: the right thing. */
>> >> >> + if (msr_index == MSR_IA32_FEATURE_CONTROL){
>> >> >> + if (to_vmx(vcpu)->nested.msr_ia32_feature_control
>> >> >> + & FEATURE_CONTROL_LOCKED)
>> >> >> + return 0;
>> >> >> + to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
>> >> > You need to allow setting it from userspace, otherwise reset will not
>> >> > clear it.
>> >> As to my memory, if the lock bit of IA32_FEATURE_CONTROL is set, this
>> >> MSR cannot be set or reset. So what do you mean setting it from
>> >> userspace?
>> > It can be reset by power cycling CPU obviously, so when userspace emulates
>> > power cycle reset it has to be able to zero the MSR. BTW you need to write
>> > corespondent QEMU patch to handle this MSR during reset and migration.
>> What is the current call trace when QEMU do system_reset? Will it
>> trigger vmx_vcpu_reset() in vmx.c?
> It will not. QEMU inits vcpu state in userspace and write it into the
> kernel with set_regs/set_srges ioctls.
So how will this achieve isolation and protection? I mean if QEMU can
reset this MSR when reboot, can user in OS also reset it? Actually,
after setting to lock bit, it cannot be set until next reboot.
>
>> >
>> >> >
>> >> >> return 1;
>> >> >> + }
>> >> >> /*
>> >> >> * No need to treat VMX capability MSRs specially: If we don't
>> >> >> handle
>> >> >> * them, handle_wrmsr will #GP(0), which is correct (they are
>> >> >> readonly)
>> >> >> @@ -5595,6 +5603,15 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>> >> >> skip_emulated_instruction(vcpu);
>> >> >> return 1;
>> >> >> }
>> >> >> +
>> >> >> +#define VMXON_NEEDED_FEATURES \
>> >> > Avi asked to use const u64 here.
>> >> >
>> >> >> + (FEATURE_CONTROL_LOCKED |
>> >> >> FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX)
>> >> >> + if ((vmx->nested.msr_ia32_feature_control &
>> >> >> VMXON_NEEDED_FEATURES)
>> >> >> + != VMXON_NEEDED_FEATURES) {
>> >> >> + kvm_inject_gp(vcpu, 0);
>> >> >> + return 1;
>> >> >> + }
>> >> >> +
>> >> >> if (enable_shadow_vmcs) {
>> >> >> shadow_vmcs = alloc_vmcs();
>> >> >> if (!shadow_vmcs)
>> >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> >> >> index e8ba99c..2d4eb8e 100644
>> >> >> --- a/arch/x86/kvm/x86.c
>> >> >> +++ b/arch/x86/kvm/x86.c
>> >> >> @@ -850,7 +850,8 @@ static u32 msrs_to_save[] = {
>> >> >> #ifdef CONFIG_X86_64
>> >> >> MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
>> >> >> #endif
>> >> >> - MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
>> >> >> + MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
>> >> >> + MSR_IA32_FEATURE_CONTROL
>> >> >> };
>> >> >>
>> >> >> static unsigned num_msrs_to_save;
>> >> >> --
>> >> >> 1.7.9.5
>> >> >
>> >> > --
>> >> > Gleb.
>> >
>> > --
>> > Gleb.
>>
>>
>>
>> --
>> Arthur Chunqi Li
>> Department of Computer Science
>> School of EECS
>> Peking University
>> Beijing, China
>
> --
> Gleb.
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