KVM: Documentation: Add the missing description for tdp_mmu_page into kvm_mmu_page

Add the description for tdp_mmu_page into kvm_mmu_page description.
tdp_mmu_page is a field to differentiate shadow pages from TDP MMU and
non-TDP MMU.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-7-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: Documentation: Add the missing description for mmu_valid_gen into kvm_mmu_page

Add the description for mmu_valid_gen into kvm_mmu_page description.
mmu_valid_gen is used in shadow MMU for fast zapping. Update the doc to
reflect that.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-6-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: Documentation: Add the missing description for tdp_mmu_root_count into kvm_mmu_page

Add the description of tdp_mmu_root_count into kvm_mmu_page description and
combine it with the description of root_count. tdp_mmu_root_count is an
atomic counter used only in TDP MMU. Update the doc.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-5-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: Documentation: Add the missing description for ptep in kvm_mmu_page

Add the missing description for ptep in kvm_mmu_page description. ptep is
used when TDP MMU is enabled and it shares the storage with parent_ptes.
Update the doc to help readers to get up-to-date info.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-4-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: Documentation: Update the field name gfns and its description in kvm_mmu_page

Update the field 'gfns' in kvm_mmu_page to 'shadowed_translation' to be
consistent with the code. Also update the corresponding 'gfns' in the
comments. The more detailed description of 'shadowed_translation' is
already inlined in the data structure definition, so no need to duplicate
the text but simply just update the names.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-3-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

KVM: Documentation: Add the missing description for guest_mode in kvm_mmu_page_role

Add the missing description for guest_mode in kvm_mmu_page_role
description. guest_mode tells KVM whether a shadow page is used for the L1
or an L2. Update the missing field in documentation.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230912184553.1887764-2-mizhang@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Documentation: Fix typos

Fix typos in Documentation.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20230814212822.193684-4-helgaas@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

KVM: x86: Fix a typo in Documentation/virt/kvm/x86/mmu.rst

L1 CR4.LA57 should be '0' instead of '1' when shadowing 5-level NPT
for 4-level NPT L1 guest.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20230518091339.1102-4-binbin.wu@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Delete duplicate words from kernel docs

I have deleted duplicate words like

to, guest, trace, when, we

Signed-off-by: Akhil Raj <lf32.dev@gmail.com>
Link: https://lore.kernel.org/r/20220829065239.4531-1-lf32.dev@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

KVM: X86/MMU: Fix shadowing 5-level NPT for 4-level NPT L1 guest

When shadowing 5-level NPT for 4-level NPT L1 guest, the root_sp is
allocated with role.level = 5 and the guest pagetable's root gfn.

And root_sp->spt[0] is also allocated with the same gfn and the same
role except role.level = 4. Luckily that they are different shadow
pages, but only root_sp->spt[0] is the real translation of the guest
pagetable.

Here comes a problem:

If the guest switches from gCR4_LA57=0 to gCR4_LA57=1 (or vice verse)
and uses the same gfn as the root page for nested NPT before and after
switching gCR4_LA57. The host (hCR4_LA57=1) might use the same root_sp
for the guest even the guest switches gCR4_LA57. The guest will see
unexpected page mapped and L2 may exploit the bug and hurt L1. It is
lucky that the problem can't hurt L0.

And three special cases need to be handled:

The root_sp should be like role.direct=1 sometimes: its contents are
not backed by gptes, root_sp->gfns is meaningless. (For a normal high
level sp in shadow paging, sp->gfns is often unused and kept zero, but
it could be relevant and meaningful if sp->gfns is used because they
are backed by concrete gptes.)

For such root_sp in the case, root_sp is just a portal to contribute
root_sp->spt[0], and root_sp->gfns should not be used and
root_sp->spt[0] should not be dropped if gpte[0] of the guest root
pagetable is changed.

Such root_sp should not be accounted too.

So add role.passthrough to distinguish the shadow pages in the hash
when gCR4_LA57 is toggled and fix above special cases by using it in
kvm_mmu_page_{get|set}_gfn() and sp_has_gptes().

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Message-Id: <20220420131204.2850-3-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation: KVM: add separate directories for architecture-specific documentation

ARM already has an arm/ subdirectory, but s390 and x86 do not even though
they have a relatively large number of files specific to them. Create
new directories in Documentation/virt/kvm for these two architectures
as well.

While at it, group the API documentation and the developer documentation
in the table of contents.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220322110712.222449-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>