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SubjectRe: [RESEND PATCH v10 03/10] mmu: spp: Add SPP Table setup functions
On Fri, Jan 10, 2020 at 09:26:11AM -0800, Sean Christopherson wrote:
> On Thu, Jan 02, 2020 at 02:13:12PM +0800, Yang Weijiang wrote:
> > SPPT is a 4-level paging structure similar to EPT, when SPP is
>
> How does SPP interact with 5-level EPT?
>
It should work, will add the test later.

> > armed for target physical page, bit 61 of the corresponding
> > EPT entry is flaged, then SPPT is traversed with the gfn,
> > the leaf entry of SPPT contains the access bitmap of subpages
> > inside the target 4KB physical page, one bit per 128-byte subpage.
> >
> > Co-developed-by: He Chen <he.chen@linux.intel.com>
> > Signed-off-by: He Chen <he.chen@linux.intel.com>
> > Co-developed-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
>
> ...
>
> > +static u64 format_spp_spte(u32 spp_wp_bitmap)
> > +{
> > + u64 new_spte = 0;
> > + int i = 0;
> > +
> > + /*
> > + * One 4K page contains 32 sub-pages, in SPP table L4E, old bits
>
> Is this
>
> One 4k page constains 32 sub-pages in SPP table L4E. Old bits are...
>
> or
> One 4k page contains 32 sub-pages. In SPP table L4E, old bits are...
>
> or
> ???
>
The second case, there's a typo, old should be odd. will modify it,
thank you!

> > + * are reserved, so we need to transfer u32 subpage write
>
> Wrap comments at 80 columns to save lines.
>
> > + * protect bitmap to u64 SPP L4E format.
>
> What is a "page" in "one 4k page"? What old bits? Why not just track a
> 64-bit value? I understand *what* the code below does, but I have no clue
> why or whether it's correct.
old should be "odd", according to SDM, the write-permission is tracked
via even bits(2i), then 32*128 = 4KB. odd bits are reserved now.
>
> > + */
> > + while (i < 32) {
> > + if (spp_wp_bitmap & (1ULL << i))
> > + new_spte |= 1ULL << (i * 2);
> > + i++;
> > + }
>
> for (i = 0; i < 32; i++)
> new_spte |= (spp_wp_bitmap & BIT_ULL(i)) << i;
>
> At the very least, use a for loop.
Sure, will change it, thank you!

>
> > +
> > + return new_spte;
> > +}
> > +
> > +static void spp_spte_set(u64 *sptep, u64 new_spte)
> > +{
> > + __set_spte(sptep, new_spte);
> > +}
> > +
> > +bool is_spp_spte(struct kvm_mmu_page *sp)
> > +{
> > + return sp->role.spp;
> > +}
> > +
> > +#define SPPT_ENTRY_PHA_MASK (0xFFFFFFFFFF << 12)
> > +
> > +int kvm_spp_setup_structure(struct kvm_vcpu *vcpu,
> > + u32 access_map, gfn_t gfn)
> > +{
> > + struct kvm_shadow_walk_iterator iter;
> > + struct kvm_mmu_page *sp;
> > + gfn_t pseudo_gfn;
> > + u64 old_spte, spp_spte;
> > + int ret = -EFAULT;
> > +
> > + /* direct_map spp start */
> > + if (!VALID_PAGE(vcpu->kvm->arch.sppt_root))
> > + return -EFAULT;
> > +
> > + for_each_shadow_spp_entry(vcpu, (u64)gfn << PAGE_SHIFT, iter) {
> > + if (iter.level == PT_PAGE_TABLE_LEVEL) {
> > + spp_spte = format_spp_spte(access_map);
> > + old_spte = mmu_spte_get_lockless(iter.sptep);
> > + if (old_spte != spp_spte)
> > + spp_spte_set(iter.sptep, spp_spte);
> > + ret = 0;
> > + break;
> > + }
> > +
> > + if (!is_shadow_present_pte(*iter.sptep)) {
> > + u64 base_addr = iter.addr;
> > +
> > + base_addr &= PT64_LVL_ADDR_MASK(iter.level);
> > + pseudo_gfn = base_addr >> PAGE_SHIFT;
> > + spp_spte = *iter.sptep;
> > + sp = kvm_spp_get_page(vcpu, pseudo_gfn,
> > + iter.level - 1);
> > + link_spp_shadow_page(vcpu, iter.sptep, sp);
> > + } else if (iter.level == PT_DIRECTORY_LEVEL &&
> > + !(spp_spte & PT_PRESENT_MASK) &&
> > + (spp_spte & SPPT_ENTRY_PHA_MASK)) {
> > + spp_spte = *iter.sptep;
> > + spp_spte |= PT_PRESENT_MASK;
> > + spp_spte_set(iter.sptep, spp_spte);
> > + }
> > + }
> > +
> > + kvm_flush_remote_tlbs(vcpu->kvm);
> > + return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(kvm_spp_setup_structure);
> > +
> > +inline u64 construct_spptp(unsigned long root_hpa)
> > +{
> > + return root_hpa & PAGE_MASK;
> > +}
> > +EXPORT_SYMBOL_GPL(construct_spptp);
> > +
> > diff --git a/arch/x86/kvm/mmu/spp.h b/arch/x86/kvm/mmu/spp.h
> > new file mode 100644
> > index 000000000000..8ef94b7a2057
> > --- /dev/null
> > +++ b/arch/x86/kvm/mmu/spp.h
> > @@ -0,0 +1,10 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __KVM_X86_VMX_SPP_H
> > +#define __KVM_X86_VMX_SPP_H
> > +
> > +bool is_spp_spte(struct kvm_mmu_page *sp);
> > +u64 construct_spptp(unsigned long root_hpa);
> > +int kvm_spp_setup_structure(struct kvm_vcpu *vcpu,
> > + u32 access_map, gfn_t gfn);
> > +
> > +#endif /* __KVM_X86_VMX_SPP_H */
> > --
> > 2.17.2
> >

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