KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 115 insertions, 0 deletions

diff --git a/Documentation/Makefile b/Documentation/Makefile
new file mode 100644
index 000000000..377a44965
--- /dev/null
+++ b/Documentation/Makefile
@@ -0,0 +1,115 @@
+# -*- makefile -*-
+# Makefile for Sphinx documentation
+#
+
+# for cleaning
+subdir- := devicetree/bindings
+
+ifneq ($(MAKECMDGOALS),cleandocs)
+# Check for broken documentation file references
+ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
+$(shell $(srctree)/tools/docs/documentation-file-ref-check --warn)
+endif
+
+# Check for broken ABI files
+ifeq ($(CONFIG_WARN_ABI_ERRORS),y)
+$(shell $(srctree)/tools/docs/get_abi.py --dir $(srctree)/Documentation/ABI validate)
+endif
+endif
+
+# You can set these variables from the command line.
+SPHINXBUILD   = sphinx-build
+SPHINXOPTS    =
+SPHINXDIRS    = .
+DOCS_THEME    =
+DOCS_CSS      =
+RUSTDOC       =
+PAPER         =
+BUILDDIR      = $(obj)/output
+PDFLATEX      = xelatex
+LATEXOPTS     = -interaction=batchmode -no-shell-escape
+
+PYTHONPYCACHEPREFIX ?= $(abspath $(BUILDDIR)/__pycache__)
+
+# Wrapper for sphinx-build
+
+BUILD_WRAPPER = $(srctree)/tools/docs/sphinx-build-wrapper
+
+# For denylisting "variable font" files
+# Can be overridden by setting as an env variable
+FONTS_CONF_DENY_VF ?= $(HOME)/deny-vf
+
+# User-friendly check for sphinx-build
+HAVE_SPHINX := $(shell if which $(SPHINXBUILD) >/dev/null 2>&1; then echo 1; else echo 0; fi)
+
+ifeq ($(HAVE_SPHINX),0)
+
+.DEFAULT:
+	$(warning The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the '$(SPHINXBUILD)' executable.)
+	@echo
+	@$(srctree)/tools/docs/sphinx-pre-install
+	@echo "  SKIP    Sphinx $@ target."
+
+else # HAVE_SPHINX
+
+# Common documentation targets
+htmldocs mandocs infodocs texinfodocs latexdocs epubdocs xmldocs pdfdocs linkcheckdocs:
+	$(Q)PYTHONPYCACHEPREFIX="$(PYTHONPYCACHEPREFIX)" \
+		$(srctree)/tools/docs/sphinx-pre-install --version-check
+	+$(Q)PYTHONPYCACHEPREFIX="$(PYTHONPYCACHEPREFIX)" \
+		$(PYTHON3) $(BUILD_WRAPPER) $@ \
+		--sphinxdirs="$(SPHINXDIRS)" $(RUSTDOC) \
+		--builddir="$(BUILDDIR)" --deny-vf=$(FONTS_CONF_DENY_VF) \
+		--theme=$(DOCS_THEME) --css=$(DOCS_CSS) --paper=$(PAPER)
+
+
+endif
+
+# The following targets are independent of HAVE_SPHINX, and the rules should
+# work or silently pass without Sphinx.
+
+htmldocs-redirects: $(srctree)/Documentation/.renames.txt
+	@tools/docs/gen-redirects.py --output $(BUILDDIR) < $<
+
+refcheckdocs:
+	$(Q)cd $(srctree); tools/docs/documentation-file-ref-check
+
+cleandocs:
+	$(Q)rm -rf $(BUILDDIR)
+
+# Used only on help
+_SPHINXDIRS   = $(shell printf "%s\n" $(patsubst $(srctree)/Documentation/%/index.rst,%,$(wildcard $(srctree)/Documentation/*/index.rst)) | sort -f)
+
+dochelp:
+	@echo  ' Linux kernel internal documentation in different formats from ReST:'
+	@echo  '  htmldocs        - HTML'
+	@echo  '  htmldocs-redirects - generate HTML redirects for moved pages'
+	@echo  '  texinfodocs     - Texinfo'
+	@echo  '  infodocs        - Info'
+	@echo  '  mandocs         - Man pages'
+	@echo  '  latexdocs       - LaTeX'
+	@echo  '  pdfdocs         - PDF'
+	@echo  '  epubdocs        - EPUB'
+	@echo  '  xmldocs         - XML'
+	@echo  '  linkcheckdocs   - check for broken external links'
+	@echo  '                    (will connect to external hosts)'
+	@echo  '  refcheckdocs    - check for references to non-existing files under'
+	@echo  '                    Documentation'
+	@echo  '  cleandocs       - clean all generated files'
+	@echo
+	@echo  '  make SPHINXDIRS="s1 s2" [target] Generate only docs of folder s1, s2'
+	@echo  '  top level values for SPHINXDIRS are:'
+	@echo  '$(_SPHINXDIRS)' | fmt -s -w 75 -g 75 | sed 's/^/    /'
+	@echo  '  you may also use a subdirectory like SPHINXDIRS=userspace-api/media,'
+	@echo  '  provided that there is an index.rst file at the subdirectory.'
+	@echo
+	@echo  '  make DOCS_THEME={sphinx-theme} selects a different Sphinx theme.'
+	@echo
+	@echo  '  make DOCS_CSS={a .css file} adds a DOCS_CSS override file for html/epub output.'
+	@echo
+	@echo  '  make PAPER={a4|letter} Specifies the paper size used for LaTeX/PDF output.'
+	@echo
+	@echo  '  make FONTS_CONF_DENY_VF={path} sets a deny list to block variable Noto CJK fonts'
+	@echo  '  for PDF build. See tools/lib/python/kdoc/latex_fonts.py for more details'
+	@echo
+	@echo  '  Default location for the generated documents is Documentation/output'