On Mon, 2022-12-19 at 15:32 +0800, Yuan Yao wrote:
> On Fri, Dec 09, 2022 at 12:45:54PM +0800, Robert Hoo wrote:
> > Define kvm_untagged_addr() per LAM feature spec: Address high bits
> > are sign
> > extended, from highest effective address bit.
> > Note that LAM_U48 and LA57 has some effective bits overlap. This
> > patch
> > gives a WARN() on that case.
> >
> > Now the only applicable possible case that addresses passed down
> > from VM
> > with LAM bits is those for MPX MSRs.
> >
> > Signed-off-by: Robert Hoo <robert.hu@xxxxxxxxxxxxxxx>
> > Reviewed-by: Jingqi Liu <jingqi.liu@xxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/vmx.c | 3 +++
> > arch/x86/kvm/x86.c | 5 +++++
> > arch/x86/kvm/x86.h | 37 +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 45 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 9985dbb63e7b..16ddd3fcd3cb 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -2134,6 +2134,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu,
> > struct msr_data *msr_info)
> > (!msr_info->host_initiated &&
> > !guest_cpuid_has(vcpu, X86_FEATURE_MPX)))
> > return 1;
> > +
> > + data = kvm_untagged_addr(data, vcpu);
> > +
> > if (is_noncanonical_address(data & PAGE_MASK, vcpu) ||
> > (data & MSR_IA32_BNDCFGS_RSVD))
> > return 1;
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index eb1f2c20e19e..0a446b45e3d6 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -1812,6 +1812,11 @@ static int __kvm_set_msr(struct kvm_vcpu
> > *vcpu, u32 index, u64 data,
> > case MSR_KERNEL_GS_BASE:
> > case MSR_CSTAR:
> > case MSR_LSTAR:
> > + /*
> > + * LAM applies only addresses used for data accesses.
>
> Confused due to the MSR_KERNEL_GS_BASE also used for data accessing,
> how about add below:
> The strict canonical checking is sitll appplied to MSR writing even
> LAM is enabled.
OK
...
> > +#ifdef CONFIG_X86_64
> > +/* untag addr for guest, according to vCPU CR3 and CR4 settings */
> > +static inline u64 kvm_untagged_addr(u64 addr, struct kvm_vcpu
> > *vcpu)
> > +{
> > + if (addr >> 63 == 0) {
> > + /* User pointers */
> > + if (kvm_read_cr3(vcpu) & X86_CR3_LAM_U57)
> > + addr = get_canonical(addr, 57);
> > + else if (kvm_read_cr3(vcpu) & X86_CR3_LAM_U48) {
> > + /*
> > + * If guest enabled 5-level paging and LAM_U48,
> > + * bit 47 should be 0, bit 48:56 contains meta
> > data
> > + * although bit 47:56 are valid 5-level address
>
> Still 48:56.
OK
