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truncate_inode_pages_range() may attempt to zero pages before truncating them, and this will occur before arch-specific invalidations can be triggered via .invalidate_folio/.free_folio hooks via kvm_gmem_aops. For AMD SEV-SNP this would result in an RMP #PF being generated by the hardware, which is currently treated as fatal (and even if specifically allowed for, would not result in anything other than garbage being written to guest pages due to encryption). On Intel TDX this would also result in undesirable behavior. Set the AS_INACCESSIBLE flag to prevent the MM from attempting unexpected accesses of this sort during operations like truncation. This may also in some cases yield a decent performance improvement for guest_memfd userspace implementations that hole-punch ranges immediately after private->shared conversions via KVM_SET_MEMORY_ATTRIBUTES, since the current implementation of truncate_inode_pages_range() always ends up zero'ing an entire 4K range if it is backing by a 2M folio. Link: https://lore.kernel.org/lkml/ZR9LYhpxTaTk6PJX@google.com/ Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Michael Roth <michael.roth@amd.com> Message-ID: <20240329212444.395559-6-michael.roth@amd.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.