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SubjectRe: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point
Friendly ping. I am hopeful one of the x86 and/or KVM maintainers has a 
few cycles to spare to look this over.

And thanks to everyone who has helped thus far by providing valuable
feedback and reviewing.


On 4/16/2018 4:09 PM, Maran Wilson wrote:
> For certain applications it is desirable to rapidly boot a KVM virtual
> machine. In cases where legacy hardware and software support within the
> guest is not needed, Qemu should be able to boot directly into the
> uncompressed Linux kernel binary without the need to run firmware.
> There already exists an ABI to allow this for Xen PVH guests and the ABI
> is supported by Linux and FreeBSD:
> This patch series would enable Qemu to use that same entry point for
> booting KVM guests.
> Changes from v6:
> * Addressed issues caught by the kbuild test robot:
> - Restored an #include line that had been dropped by mistake (patch 4)
> - Removed a pair of #include lines that were no longer needed in a
> common code file and causing problems for certain 32-bit configs
> (patchs 4 and 7)
> Changes from v5:
> * The interface changes to the x86/HVM start info layout have
> now been accepted into the Xen tree.
> * Rebase and merge upstream PVH file changes.
> * (Patch 6) Synced up to the final version of the header file that was
> acked and pulled into the Xen tree.
> * (Patch 1) Fixed typo and removed redundant "def_bool n" line.
> Changes from v4:
> Note: I've withheld Juergen's earlier "Reviewed-by" tags from patches
> 1 and 7 since there were minor changes (mostly just addition of
> CONFIG_KVM_GUEST_PVH as requested) that came afterwards.
> * Changed subject prefix from RFC to PATCH
> * Added CONFIG_KVM_GUEST_PVH as suggested
> * Relocated the PVH common files to
> arch/x86/platform/pvh/{enlighten.c,head.S}
> * Realized I also needed to move the objtool override for those files
> * Updated a few code comments per reviewer feedback
> * Sent out a patch of the hvm_start_info struct changes against the Xen
> tree since that is the canonical copy of the header. Discussions on
> that thread have resulted in some (non-functional) updates to
> start_info.h (patch 6/7) and those changes are reflected here as well
> in order to keep the files in sync. The header file has since been
> ack'ed for the Xen tree by Jan Beulich.
> Changes from v3:
> * Implemented Juergen's suggestion for refactoring and moving the PVH
> code so that CONFIG_XEN is no longer required for booting KVM guests
> via the PVH entry point.
> Functionally, nothing has changed from V3 really, but the patches
> look completely different now because of all the code movement and
> refactoring. Some of these patches can be combined, but I've left
> them very small in some cases to make the refactoring and code
> movement easier to review.
> My approach for refactoring has been to create a PVH entry layer that
> still has understanding and knowledge about Xen vs non-Xen guest types
> so that it can make run time decisions to handle either case, as
> opposed to going all the way and re-writing it to be a completely
> hypervisor agnostic and architecturally pure layer that is separate
> from guest type details. The latter seemed a bit overkill in this
> situation. And I've handled the complexity of having to support
> Qemu/KVM boot of kernels compiled with or without CONFIG_XEN via a
> pair of xen specific __weak routines that can be overridden in kernels
> that support Xen guests. Importantly, the __weak routines are for
> xen specific code only (not generic "guest type" specific code) so
> there is no clashing between xen version of the strong routine and,
> say, a KVM version of the same routine. But I'm sure there are many
> ways to skin this cat, so I'm open to alternate suggestions if there
> is a compelling reason for not using __weak in this situation.
> Changes from v2:
> * All structures (including memory map table entries) are padded and
> aligned to an 8 byte boundary.
> * Removed the "packed" attributes and made changes to comments as
> suggested by Jan.
> Changes from v1:
> * Adopted Paolo's suggestion for defining a v2 PVH ABI that includes the
> e820 map instead of using the second module entry to pass the table.
> * Cleaned things up a bit to reduce the number of xen vs non-xen special
> cases.
> Maran Wilson (7):
> xen/pvh: Move PVH entry code out of Xen specific tree
> xen/pvh: Create a new file for Xen specific PVH code
> xen/pvh: Move Xen specific PVH VM initialization out of common file
> xen/pvh: Move Xen code for getting mem map via hcall out of common
> file
> xen/pvh: Add memory map pointer to hvm_start_info struct
> KVM: x86: Allow Qemu/KVM to use PVH entry point
> arch/x86/Kbuild | 2 +
> arch/x86/Kconfig | 14 +++
> arch/x86/kernel/head_64.S | 2 +-
> arch/x86/platform/pvh/Makefile | 5 +
> arch/x86/platform/pvh/enlighten.c | 136 ++++++++++++++++++++++++
> arch/x86/{xen/xen-pvh.S => platform/pvh/head.S} | 0
> arch/x86/xen/Kconfig | 3 +-
> arch/x86/xen/Makefile | 2 -
> arch/x86/xen/enlighten_pvh.c | 93 +++-------------
> include/xen/interface/hvm/start_info.h | 63 ++++++++++-
> 11 files changed, 240 insertions(+), 81 deletions(-)
> create mode 100644 arch/x86/platform/pvh/Makefile
> create mode 100644 arch/x86/platform/pvh/enlighten.c
> rename arch/x86/{xen/xen-pvh.S => platform/pvh/head.S} (100%)

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