On Tue, Jan 17, 2023 at 03:11:46AM +0000,
"Huang, Kai" <kai.huang@xxxxxxxxx> wrote:
> On Thu, 2023-01-12 at 08:32 -0800, isaku.yamahata@xxxxxxxxx wrote:
> > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> >
> > Although TDX supports only WB for private GPA, MTRR/PAT for shared GPA
> > should be supported. Implement get_mt_mask() following vmx case.
>
> By far this is the first patch to handle MTRR/PAT. There's absolutely no
> background have been explained.
>
> So what about MTRR/PAT related MSRs handling? No code needed to handle?
>
> I was expecting there should be at least some words here to explain how TDX
> handles them, and if no handling is required in KVM, why.
>
> W/o those, I don't think this patch is reviewable.
I've updated the commit message.
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/main.c | 10 +++++++++-
> > arch/x86/kvm/vmx/tdx.c | 19 +++++++++++++++++++
> > arch/x86/kvm/vmx/x86_ops.h | 2 ++
> > 3 files changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> > index 770d1b29d1c3..4319f6d7a4da 100644
> > --- a/arch/x86/kvm/vmx/main.c
> > +++ b/arch/x86/kvm/vmx/main.c
> > @@ -158,6 +158,14 @@ static void vt_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
> > vmx_load_mmu_pgd(vcpu, root_hpa, pgd_level);
> > }
> >
> > +static u8 vt_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> > +{
> > + if (is_td_vcpu(vcpu))
> > + return tdx_get_mt_mask(vcpu, gfn, is_mmio);
> > +
> > + return vmx_get_mt_mask(vcpu, gfn, is_mmio);
> > +}
> > +
> > static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
> > {
> > if (!is_td(kvm))
> > @@ -267,7 +275,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> >
> > .set_tss_addr = vmx_set_tss_addr,
> > .set_identity_map_addr = vmx_set_identity_map_addr,
> > - .get_mt_mask = vmx_get_mt_mask,
> > + .get_mt_mask = vt_get_mt_mask,
> >
> > .get_exit_info = vmx_get_exit_info,
> >
> > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > index e68816999387..c4c5a8f786c1 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -309,6 +309,25 @@ int tdx_vm_init(struct kvm *kvm)
> > return 0;
> > }
> >
> > +u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> > +{
> > + /* TDX private GPA is always WB. */
> > + if (gfn & kvm_gfn_shared_mask(vcpu->kvm)) {
>
> First of all, private GPA doesn't have 'shared bit' set, so comment doesn't
> reflect code.
>
> Secondly (and again), IIUC the shared bit of the gfn has been stripped out long
> time ago, so this is incorrect.
>
> Please don't sliently ignore other people's comment:
>
> https://lore.kernel.org/lkml/Y19NzlQcwhV%2F2wl3@xxxxxxxxx/T/#mf319d5b718519709362f9f094bfc5b53fd870241
Make the logic common for vmx and tdx. the difference is to check cr0.cd.
Thanks,
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
