[PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

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:

   https://xenbits.xen.org/docs/unstable/misc/pvh.html

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: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH
  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

 MAINTAINERS                                     |   1 +
 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%)

-- 
2.16.1

[PATCH v7 1/7] xen/pvh: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH

[Maran Wilson]

In order to pave the way for hypervisors other than Xen to use the PVH
entry point for VMs, we need to factor the PVH entry code into Xen specific
and hypervisor agnostic components. The first step in doing that, is to
create a new config option for PVH entry that can be enabled
independently from CONFIG_XEN.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
---
 arch/x86/Kconfig          | 6 ++++++
 arch/x86/kernel/head_64.S | 2 +-
 arch/x86/xen/Kconfig      | 3 ++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d234cca296db..8511d419e39f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -781,6 +781,12 @@ config KVM_GUEST
 	  underlying device model, the host provides the guest with
 	  timing infrastructure such as time of day, and system time
 
+config PVH
+	bool "Support for running PVH guests"
+	---help---
+	  This option enables the PVH entry point for guest virtual machines
+	  as specified in the x86/HVM direct boot ABI.
+
 config KVM_DEBUG_FS
 	bool "Enable debug information for KVM Guests in debugfs"
 	depends on KVM_GUEST && DEBUG_FS
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 48385c1074a5..d83f2b110b47 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -385,7 +385,7 @@ NEXT_PAGE(early_dynamic_pgts)
 
 	.data
 
-#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
+#if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH)
 NEXT_PGD_PAGE(init_top_pgt)
 	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
 	.org    init_top_pgt + L4_PAGE_OFFSET*8, 0
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index c1f98f32c45f..5fccee76f44d 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -74,6 +74,7 @@ config XEN_DEBUG_FS
 	  Enabling this option may incur a significant performance overhead.
 
 config XEN_PVH
-	bool "Support for running as a PVH guest"
+	bool "Support for running as a Xen PVH guest"
 	depends on XEN && XEN_PVHVM && ACPI
+	select PVH
 	def_bool n
-- 
2.16.1

[PATCH v7 2/7] xen/pvh: Move PVH entry code out of Xen specific tree

[Maran Wilson]

Once hypervisors other than Xen start using the PVH entry point for
starting VMs, we would like the option of being able to compile PVH entry
capable kernels without enabling CONFIG_XEN and all the code that comes
along with that. To allow that, we are moving the PVH code out of Xen and
into files sitting at a higher level in the tree.

This patch is not introducing any code or functional changes, just moving
files from one location to another.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 MAINTAINERS                                                | 1 +
 arch/x86/Kbuild                                            | 2 ++
 arch/x86/platform/pvh/Makefile                             | 5 +++++
 arch/x86/{xen/enlighten_pvh.c => platform/pvh/enlighten.c} | 0
 arch/x86/{xen/xen-pvh.S => platform/pvh/head.S}            | 0
 arch/x86/xen/Makefile                                      | 3 ---
 6 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/platform/pvh/Makefile
 rename arch/x86/{xen/enlighten_pvh.c => platform/pvh/enlighten.c} (100%)
 rename arch/x86/{xen/xen-pvh.S => platform/pvh/head.S} (100%)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7bb2e9595f14..0b816f588fe1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15385,6 +15385,7 @@ L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
 S:	Supported
 F:	arch/x86/xen/
+F:	arch/x86/platform/pvh/
 F:	drivers/*/xen-*front.c
 F:	drivers/xen/
 F:	arch/x86/include/asm/xen/
diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index 0038a2d10a7a..2089e4414300 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -7,6 +7,8 @@ obj-$(CONFIG_KVM) += kvm/
 # Xen paravirtualization support
 obj-$(CONFIG_XEN) += xen/
 
+obj-$(CONFIG_XEN_PVH) += platform/pvh/
+
 # Hyper-V paravirtualization support
 obj-$(subst m,y,$(CONFIG_HYPERV)) += hyperv/
 
diff --git a/arch/x86/platform/pvh/Makefile b/arch/x86/platform/pvh/Makefile
new file mode 100644
index 000000000000..9fd25efcd2a3
--- /dev/null
+++ b/arch/x86/platform/pvh/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+OBJECT_FILES_NON_STANDARD_head.o := y
+
+obj-$(CONFIG_XEN_PVH) += enlighten.o
+obj-$(CONFIG_XEN_PVH) += head.o
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/platform/pvh/enlighten.c
similarity index 100%
rename from arch/x86/xen/enlighten_pvh.c
rename to arch/x86/platform/pvh/enlighten.c
diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/platform/pvh/head.S
similarity index 100%
rename from arch/x86/xen/xen-pvh.S
rename to arch/x86/platform/pvh/head.S
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index d83cb5478f54..f1b850607212 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y
-OBJECT_FILES_NON_STANDARD_xen-pvh.o := y
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
@@ -21,7 +20,6 @@ obj-y		:= enlighten.o multicalls.o mmu.o irq.o \
 obj-$(CONFIG_XEN_PVHVM)		+= enlighten_hvm.o mmu_hvm.o suspend_hvm.o
 obj-$(CONFIG_XEN_PV)			+= setup.o apic.o pmu.o suspend_pv.o \
 						p2m.o enlighten_pv.o mmu_pv.o
-obj-$(CONFIG_XEN_PVH)			+= enlighten_pvh.o
 
 obj-$(CONFIG_EVENT_TRACING) += trace.o
 
@@ -33,4 +31,3 @@ obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_XEN_DOM0)		+= vga.o
 obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
 obj-$(CONFIG_XEN_EFI)		+= efi.o
-obj-$(CONFIG_XEN_PVH)	 	+= xen-pvh.o
-- 
2.16.1

[PATCH v7 3/7] xen/pvh: Create a new file for Xen specific PVH code

[Maran Wilson]

We need to refactor PVH entry code so that support for other hypervisors
like Qemu/KVM can be added more easily.

The first step in that direction is to create a new file that will
eventually hold the Xen specific routines.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
---
 arch/x86/platform/pvh/enlighten.c | 5 ++---
 arch/x86/xen/Makefile             | 1 +
 arch/x86/xen/enlighten_pvh.c      | 9 +++++++++
 3 files changed, 12 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/xen/enlighten_pvh.c

diff --git a/arch/x86/platform/pvh/enlighten.c b/arch/x86/platform/pvh/enlighten.c
index aa1c6a6831a9..74ff1c3d2789 100644
--- a/arch/x86/platform/pvh/enlighten.c
+++ b/arch/x86/platform/pvh/enlighten.c
@@ -17,10 +17,9 @@
 /*
  * PVH variables.
  *
- * xen_pvh pvh_bootparams and pvh_start_info need to live in data segment
- * since they are used after startup_{32|64}, which clear .bss, are invoked.
+ * pvh_bootparams and pvh_start_info need to live in the data segment since
+ * they are used after startup_{32|64}, which clear .bss, are invoked.
  */
-bool xen_pvh __attribute__((section(".data"))) = 0;
 struct boot_params pvh_bootparams __attribute__((section(".data")));
 struct hvm_start_info pvh_start_info __attribute__((section(".data")));
 
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index f1b850607212..ae5c6f1f0fe0 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -20,6 +20,7 @@ obj-y		:= enlighten.o multicalls.o mmu.o irq.o \
 obj-$(CONFIG_XEN_PVHVM)		+= enlighten_hvm.o mmu_hvm.o suspend_hvm.o
 obj-$(CONFIG_XEN_PV)			+= setup.o apic.o pmu.o suspend_pv.o \
 						p2m.o enlighten_pv.o mmu_pv.o
+obj-$(CONFIG_XEN_PVH)			+= enlighten_pvh.o
 
 obj-$(CONFIG_EVENT_TRACING) += trace.o
 
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
new file mode 100644
index 000000000000..313fe499065e
--- /dev/null
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -0,0 +1,9 @@
+#include <linux/types.h>
+
+/*
+ * PVH variables.
+ *
+ * The variable xen_pvh needs to live in the data segment since it is used
+ * after startup_{32|64} is invoked, which will clear the .bss segment.
+ */
+bool xen_pvh __attribute__((section(".data"))) = 0;
-- 
2.16.1

[PATCH v7 4/7] xen/pvh: Move Xen specific PVH VM initialization out of common file

[Maran Wilson]

We need to refactor PVH entry code so that support for other hypervisors
like Qemu/KVM can be added more easily.

This patch moves the small block of code used for initializing Xen PVH
virtual machines into the Xen specific file. This initialization is not
going to be needed for Qemu/KVM guests. Moving it out of the common file
is going to allow us to compile kernels in the future without CONFIG_XEN
that are still capable of being booted as a Qemu/KVM guest via the PVH
entry point.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/platform/pvh/enlighten.c | 28 ++++++++++++++++++++--------
 arch/x86/xen/enlighten_pvh.c      | 20 +++++++++++++++++++-
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/arch/x86/platform/pvh/enlighten.c b/arch/x86/platform/pvh/enlighten.c
index 74ff1c3d2789..edcff7de0529 100644
--- a/arch/x86/platform/pvh/enlighten.c
+++ b/arch/x86/platform/pvh/enlighten.c
@@ -80,26 +80,38 @@ static void __init init_pvh_bootparams(void)
 	x86_init.acpi.get_root_pointer = pvh_get_root_pointer;
 }
 
+/*
+ * If we are trying to boot a Xen PVH guest, it is expected that the kernel
+ * will have been configured to provide the required override for this routine.
+ */
+void __init __weak xen_pvh_init(void)
+{
+	xen_raw_printk("Error: Missing xen PVH initialization\n");
+	BUG();
+}
+
+/*
+ * When we add support for other hypervisors like Qemu/KVM, this routine can
+ * selectively invoke the appropriate initialization based on guest type.
+ */
+static void hypervisor_specific_init(void)
+{
+	xen_pvh_init();
+}
+
 /*
  * This routine (and those that it might call) should not use
  * anything that lives in .bss since that segment will be cleared later.
  */
 void __init xen_prepare_pvh(void)
 {
-	u32 msr;
-	u64 pfn;
-
 	if (pvh_start_info.magic != XEN_HVM_START_MAGIC_VALUE) {
 		xen_raw_printk("Error: Unexpected magic value (0x%08x)\n",
 				pvh_start_info.magic);
 		BUG();
 	}
 
-	xen_pvh = 1;
-
-	msr = cpuid_ebx(xen_cpuid_base() + 2);
-	pfn = __pa(hypercall_page);
-	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
+	hypervisor_specific_init();
 
 	init_pvh_bootparams();
 }
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index 313fe499065e..bb5784f354b8 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -1,4 +1,10 @@
-#include <linux/types.h>
+#include <linux/acpi.h>
+
+#include <asm/io_apic.h>
+#include <asm/hypervisor.h>
+
+#include <asm/xen/interface.h>
+#include <asm/xen/hypercall.h>
 
 /*
  * PVH variables.
@@ -7,3 +13,15 @@
  * after startup_{32|64} is invoked, which will clear the .bss segment.
  */
 bool xen_pvh __attribute__((section(".data"))) = 0;
+
+void __init xen_pvh_init(void)
+{
+	u32 msr;
+	u64 pfn;
+
+	xen_pvh = 1;
+
+	msr = cpuid_ebx(xen_cpuid_base() + 2);
+	pfn = __pa(hypercall_page);
+	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
+}
-- 
2.16.1

[PATCH v7 5/7] xen/pvh: Move Xen code for getting mem map via hcall out of common file

[Maran Wilson]

We need to refactor PVH entry code so that support for other hypervisors
like Qemu/KVM can be added more easily.

The original design for PVH entry in Xen guests relies on being able to
obtain the memory map from the hypervisor using a hypercall. When we
extend the PVH entry ABI to support other hypervisors like Qemu/KVM,
a new mechanism will be added that allows the guest to get the memory
map without needing to use hypercalls.

For Xen guests, the hypercall approach will still be supported. In
preparation for adding support for other hypervisors, we can move the
code that uses hypercalls into the Xen specific file. This will allow us
to compile kernels in the future without CONFIG_XEN that are still capable
of being booted as a Qemu/KVM guest via the PVH entry point.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/platform/pvh/enlighten.c | 29 ++++++++++++++---------------
 arch/x86/xen/enlighten_pvh.c      | 20 ++++++++++++++++++++
 2 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/arch/x86/platform/pvh/enlighten.c b/arch/x86/platform/pvh/enlighten.c
index edcff7de0529..c42a9f36ee9c 100644
--- a/arch/x86/platform/pvh/enlighten.c
+++ b/arch/x86/platform/pvh/enlighten.c
@@ -8,10 +8,6 @@
 #include <asm/e820/api.h>
 #include <asm/x86_init.h>
 
-#include <asm/xen/interface.h>
-#include <asm/xen/hypercall.h>
-
-#include <xen/interface/memory.h>
 #include <xen/interface/hvm/start_info.h>
 
 /*
@@ -30,21 +26,24 @@ static u64 pvh_get_root_pointer(void)
 	return pvh_start_info.rsdp_paddr;
 }
 
+/*
+ * Xen guests are able to obtain the memory map from the hypervisor via the
+ * HYPERVISOR_memory_op hypercall.
+ * If we are trying to boot a Xen PVH guest, it is expected that the kernel
+ * will have been configured to provide an override for this routine to do
+ * just that.
+ */
+void __init __weak mem_map_via_hcall(struct boot_params *ptr __maybe_unused)
+{
+	xen_raw_printk("Error: Could not find memory map\n");
+	BUG();
+}
+
 static void __init init_pvh_bootparams(void)
 {
-	struct xen_memory_map memmap;
-	int rc;
-
 	memset(&pvh_bootparams, 0, sizeof(pvh_bootparams));
 
-	memmap.nr_entries = ARRAY_SIZE(pvh_bootparams.e820_table);
-	set_xen_guest_handle(memmap.buffer, pvh_bootparams.e820_table);
-	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
-	if (rc) {
-		xen_raw_printk("XENMEM_memory_map failed (%d)\n", rc);
-		BUG();
-	}
-	pvh_bootparams.e820_entries = memmap.nr_entries;
+	mem_map_via_hcall(&pvh_bootparams);
 
 	if (pvh_bootparams.e820_entries < E820_MAX_ENTRIES_ZEROPAGE - 1) {
 		pvh_bootparams.e820_table[pvh_bootparams.e820_entries].addr =
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index bb5784f354b8..0141dd1d21e2 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -1,11 +1,16 @@
 #include <linux/acpi.h>
 
+#include <xen/hvc-console.h>
+
 #include <asm/io_apic.h>
 #include <asm/hypervisor.h>
+#include <asm/e820/api.h>
 
 #include <asm/xen/interface.h>
 #include <asm/xen/hypercall.h>
 
+#include <xen/interface/memory.h>
+
 /*
  * PVH variables.
  *
@@ -25,3 +30,18 @@ void __init xen_pvh_init(void)
 	pfn = __pa(hypercall_page);
 	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
 }
+
+void __init mem_map_via_hcall(struct boot_params *boot_params_p)
+{
+	struct xen_memory_map memmap;
+	int rc;
+
+	memmap.nr_entries = ARRAY_SIZE(boot_params_p->e820_table);
+	set_xen_guest_handle(memmap.buffer, boot_params_p->e820_table);
+	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+	if (rc) {
+		xen_raw_printk("XENMEM_memory_map failed (%d)\n", rc);
+		BUG();
+	}
+	boot_params_p->e820_entries = memmap.nr_entries;
+}
-- 
2.16.1

[PATCH v7 6/7] xen/pvh: Add memory map pointer to hvm_start_info struct

[Maran Wilson]

The start info structure that is defined as part of the x86/HVM direct boot
ABI and used for starting Xen PVH guests would be more versatile if it also
included a way to pass information about the memory map to the guest. This
would allow KVM guests to share the same entry point.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
---
 include/xen/interface/hvm/start_info.h | 63 +++++++++++++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/include/xen/interface/hvm/start_info.h b/include/xen/interface/hvm/start_info.h
index 648415976ead..50af9ea2ff1e 100644
--- a/include/xen/interface/hvm/start_info.h
+++ b/include/xen/interface/hvm/start_info.h
@@ -33,7 +33,7 @@
  *    | magic          | Contains the magic value XEN_HVM_START_MAGIC_VALUE
  *    |                | ("xEn3" with the 0x80 bit of the "E" set).
  *  4 +----------------+
- *    | version        | Version of this structure. Current version is 0. New
+ *    | version        | Version of this structure. Current version is 1. New
  *    |                | versions are guaranteed to be backwards-compatible.
  *  8 +----------------+
  *    | flags          | SIF_xxx flags.
@@ -48,6 +48,15 @@
  * 32 +----------------+
  *    | rsdp_paddr     | Physical address of the RSDP ACPI data structure.
  * 40 +----------------+
+ *    | memmap_paddr   | Physical address of the (optional) memory map. Only
+ *    |                | present in version 1 and newer of the structure.
+ * 48 +----------------+
+ *    | memmap_entries | Number of entries in the memory map table. Zero
+ *    |                | if there is no memory map being provided. Only
+ *    |                | present in version 1 and newer of the structure.
+ * 52 +----------------+
+ *    | reserved       | Version 1 and newer only.
+ * 56 +----------------+
  *
  * The layout of each entry in the module structure is the following:
  *
@@ -62,13 +71,51 @@
  *    | reserved       |
  * 32 +----------------+
  *
+ * The layout of each entry in the memory map table is as follows:
+ *
+ *  0 +----------------+
+ *    | addr           | Base address
+ *  8 +----------------+
+ *    | size           | Size of mapping in bytes
+ * 16 +----------------+
+ *    | type           | Type of mapping as defined between the hypervisor
+ *    |                | and guest. See XEN_HVM_MEMMAP_TYPE_* values below.
+ * 20 +----------------|
+ *    | reserved       |
+ * 24 +----------------+
+ *
  * The address and sizes are always a 64bit little endian unsigned integer.
  *
  * NB: Xen on x86 will always try to place all the data below the 4GiB
  * boundary.
+ *
+ * Version numbers of the hvm_start_info structure have evolved like this:
+ *
+ * Version 0:  Initial implementation.
+ *
+ * Version 1:  Added the memmap_paddr/memmap_entries fields (plus 4 bytes of
+ *             padding) to the end of the hvm_start_info struct. These new
+ *             fields can be used to pass a memory map to the guest. The
+ *             memory map is optional and so guests that understand version 1
+ *             of the structure must check that memmap_entries is non-zero
+ *             before trying to read the memory map.
  */
 #define XEN_HVM_START_MAGIC_VALUE 0x336ec578
 
+/*
+ * The values used in the type field of the memory map table entries are
+ * defined below and match the Address Range Types as defined in the "System
+ * Address Map Interfaces" section of the ACPI Specification. Please refer to
+ * section 15 in version 6.2 of the ACPI spec: http://uefi.org/specifications
+ */
+#define XEN_HVM_MEMMAP_TYPE_RAM       1
+#define XEN_HVM_MEMMAP_TYPE_RESERVED  2
+#define XEN_HVM_MEMMAP_TYPE_ACPI      3
+#define XEN_HVM_MEMMAP_TYPE_NVS       4
+#define XEN_HVM_MEMMAP_TYPE_UNUSABLE  5
+#define XEN_HVM_MEMMAP_TYPE_DISABLED  6
+#define XEN_HVM_MEMMAP_TYPE_PMEM      7
+
 /*
  * C representation of the x86/HVM start info layout.
  *
@@ -86,6 +133,13 @@ struct hvm_start_info {
     uint64_t cmdline_paddr;     /* Physical address of the command line.     */
     uint64_t rsdp_paddr;        /* Physical address of the RSDP ACPI data    */
                                 /* structure.                                */
+    /* All following fields only present in version 1 and newer */
+    uint64_t memmap_paddr;      /* Physical address of an array of           */
+                                /* hvm_memmap_table_entry.                   */
+    uint32_t memmap_entries;    /* Number of entries in the memmap table.    */
+                                /* Value will be zero if there is no memory  */
+                                /* map being provided.                       */
+    uint32_t reserved;          /* Must be zero.                             */
 };
 
 struct hvm_modlist_entry {
@@ -95,4 +149,11 @@ struct hvm_modlist_entry {
     uint64_t reserved;
 };
 
+struct hvm_memmap_table_entry {
+    uint64_t addr;              /* Base address of the memory region         */
+    uint64_t size;              /* Size of the memory region in bytes        */
+    uint32_t type;              /* Mapping type                              */
+    uint32_t reserved;          /* Must be zero for Version 1.               */
+};
+
 #endif /* __XEN_PUBLIC_ARCH_X86_HVM_START_INFO_H__ */
-- 
2.16.1

[PATCH v7 7/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

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:

   https://xenbits.xen.org/docs/unstable/misc/pvh.html

This patch enables Qemu to use that same entry point for booting KVM
guests.

Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
Suggested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Suggested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 arch/x86/Kbuild                   |  2 +-
 arch/x86/Kconfig                  |  8 ++++++++
 arch/x86/platform/pvh/Makefile    |  4 ++--
 arch/x86/platform/pvh/enlighten.c | 42 +++++++++++++++++++++++++++++----------
 4 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index 2089e4414300..c625f57472f7 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -7,7 +7,7 @@ obj-$(CONFIG_KVM) += kvm/
 # Xen paravirtualization support
 obj-$(CONFIG_XEN) += xen/
 
-obj-$(CONFIG_XEN_PVH) += platform/pvh/
+obj-$(CONFIG_PVH) += platform/pvh/
 
 # Hyper-V paravirtualization support
 obj-$(subst m,y,$(CONFIG_HYPERV)) += hyperv/
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8511d419e39f..26fef538d3ef 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -787,6 +787,14 @@ config PVH
 	  This option enables the PVH entry point for guest virtual machines
 	  as specified in the x86/HVM direct boot ABI.
 
+config KVM_GUEST_PVH
+	bool "Support for running as a KVM PVH guest"
+	depends on KVM_GUEST
+	select PVH
+	---help---
+	  This option enables starting KVM guests via the PVH entry point as
+	  specified in the x86/HVM direct boot ABI.
+
 config KVM_DEBUG_FS
 	bool "Enable debug information for KVM Guests in debugfs"
 	depends on KVM_GUEST && DEBUG_FS
diff --git a/arch/x86/platform/pvh/Makefile b/arch/x86/platform/pvh/Makefile
index 9fd25efcd2a3..5dec5067c9fb 100644
--- a/arch/x86/platform/pvh/Makefile
+++ b/arch/x86/platform/pvh/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 OBJECT_FILES_NON_STANDARD_head.o := y
 
-obj-$(CONFIG_XEN_PVH) += enlighten.o
-obj-$(CONFIG_XEN_PVH) += head.o
+obj-$(CONFIG_PVH) += enlighten.o
+obj-$(CONFIG_PVH) += head.o
diff --git a/arch/x86/platform/pvh/enlighten.c b/arch/x86/platform/pvh/enlighten.c
index c42a9f36ee9c..0c7f570d3c16 100644
--- a/arch/x86/platform/pvh/enlighten.c
+++ b/arch/x86/platform/pvh/enlighten.c
@@ -8,6 +8,8 @@
 #include <asm/e820/api.h>
 #include <asm/x86_init.h>
 
+#include <asm/xen/interface.h>
+
 #include <xen/interface/hvm/start_info.h>
 
 /*
@@ -39,11 +41,28 @@ void __init __weak mem_map_via_hcall(struct boot_params *ptr __maybe_unused)
 	BUG();
 }
 
-static void __init init_pvh_bootparams(void)
+static void __init init_pvh_bootparams(bool xen_guest)
 {
 	memset(&pvh_bootparams, 0, sizeof(pvh_bootparams));
 
-	mem_map_via_hcall(&pvh_bootparams);
+	if ((pvh_start_info.version > 0) && (pvh_start_info.memmap_entries)) {
+		struct hvm_memmap_table_entry *ep;
+		int i;
+
+		ep = __va(pvh_start_info.memmap_paddr);
+		pvh_bootparams.e820_entries = pvh_start_info.memmap_entries;
+
+		for (i = 0; i < pvh_bootparams.e820_entries ; i++, ep++) {
+			pvh_bootparams.e820_table[i].addr = ep->addr;
+			pvh_bootparams.e820_table[i].size = ep->size;
+			pvh_bootparams.e820_table[i].type = ep->type;
+		}
+	} else if (xen_guest) {
+		mem_map_via_hcall(&pvh_bootparams);
+	} else {
+		/* Non-xen guests are not supported by version 0 */
+		BUG();
+	}
 
 	if (pvh_bootparams.e820_entries < E820_MAX_ENTRIES_ZEROPAGE - 1) {
 		pvh_bootparams.e820_table[pvh_bootparams.e820_entries].addr =
@@ -74,7 +93,7 @@ static void __init init_pvh_bootparams(void)
 	 * environment (i.e. hardware_subarch 0).
 	 */
 	pvh_bootparams.hdr.version = 0x212;
-	pvh_bootparams.hdr.type_of_loader = (9 << 4) | 0; /* Xen loader */
+	pvh_bootparams.hdr.type_of_loader = ((xen_guest ? 0x9 : 0xb) << 4) | 0;
 
 	x86_init.acpi.get_root_pointer = pvh_get_root_pointer;
 }
@@ -89,13 +108,10 @@ void __init __weak xen_pvh_init(void)
 	BUG();
 }
 
-/*
- * When we add support for other hypervisors like Qemu/KVM, this routine can
- * selectively invoke the appropriate initialization based on guest type.
- */
-static void hypervisor_specific_init(void)
+static void hypervisor_specific_init(bool xen_guest)
 {
-	xen_pvh_init();
+	if (xen_guest)
+		xen_pvh_init();
 }
 
 /*
@@ -104,13 +120,17 @@ static void hypervisor_specific_init(void)
  */
 void __init xen_prepare_pvh(void)
 {
+
+	u32 msr = xen_cpuid_base();
+	bool xen_guest = !!msr;
+
 	if (pvh_start_info.magic != XEN_HVM_START_MAGIC_VALUE) {
 		xen_raw_printk("Error: Unexpected magic value (0x%08x)\n",
 				pvh_start_info.magic);
 		BUG();
 	}
 
-	hypervisor_specific_init();
+	hypervisor_specific_init(xen_guest);
 
-	init_pvh_bootparams();
+	init_pvh_bootparams(xen_guest);
 }
-- 
2.16.1

Re: [PATCH v7 1/7] xen/pvh: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH

[Juergen Gross]

On 17/04/18 01:11, Maran Wilson wrote:
> In order to pave the way for hypervisors other than Xen to use the PVH
> entry point for VMs, we need to factor the PVH entry code into Xen specific
> and hypervisor agnostic components. The first step in doing that, is to
> create a new config option for PVH entry that can be enabled
> independently from CONFIG_XEN.
> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v7 2/7] xen/pvh: Move PVH entry code out of Xen specific tree

[Juergen Gross]

On 17/04/18 01:11, Maran Wilson wrote:
> Once hypervisors other than Xen start using the PVH entry point for
> starting VMs, we would like the option of being able to compile PVH entry
> capable kernels without enabling CONFIG_XEN and all the code that comes
> along with that. To allow that, we are moving the PVH code out of Xen and
> into files sitting at a higher level in the tree.
> 
> This patch is not introducing any code or functional changes, just moving
> files from one location to another.
> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v7 3/7] xen/pvh: Create a new file for Xen specific PVH code

[Juergen Gross]

On 17/04/18 01:12, Maran Wilson wrote:
> We need to refactor PVH entry code so that support for other hypervisors
> like Qemu/KVM can be added more easily.
> 
> The first step in that direction is to create a new file that will
> eventually hold the Xen specific routines.
> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v7 6/7] xen/pvh: Add memory map pointer to hvm_start_info struct

[Juergen Gross]

On 17/04/18 01:13, Maran Wilson wrote:
> The start info structure that is defined as part of the x86/HVM direct boot
> ABI and used for starting Xen PVH guests would be more versatile if it also
> included a way to pass information about the memory map to the guest. This
> would allow KVM guests to share the same entry point.
> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v7 7/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Juergen Gross]

On 17/04/18 01:13, 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:
> 
>    https://xenbits.xen.org/docs/unstable/misc/pvh.html
> 
> This patch enables Qemu to use that same entry point for booting KVM
> guests.
> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
> Suggested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Suggested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Reviewed-by: Juergen Gross <jgross@suse.com>

You might want to send a follow-up patch to rename the functions in
arch/x86/platform/pvh/* from xen_* to pvh_*.


Juergen

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Linus Walleij]

I wonder why I am starting to get CCed on Xen patches all of a sudden.

I happened to run into Jürgen at a conference only last weekend, but
I still don't know anything whatsoever about Xen or how it works.

If get_maintainer.pl has started to return my name on this stuff I
really want to know why :/

Yours,
Linus Walleij

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

On 4/18/2018 1:11 AM, Linus Walleij wrote:
> I wonder why I am starting to get CCed on Xen patches all of a sudden.
>
> I happened to run into Jürgen at a conference only last weekend, but
> I still don't know anything whatsoever about Xen or how it works.
>
> If get_maintainer.pl has started to return my name on this stuff I
> really want to know why :/

It has nothing to do with Xen actually. But for some reason, the 
get_maintainer.pl script is returning your name for any patch that 
modifies the MAINTAINERS file. Although why that is the case wasn't 
clear to me based on a quick look at both those files.

-Maran

> Yours,
> Linus Walleij

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

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.

    https://lkml.org/lkml/2018/4/16/1002

Thanks,
-Maran

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:
>
>     https://xenbits.xen.org/docs/unstable/misc/pvh.html
>
> 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: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH
>    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
>
>   MAINTAINERS                                     |   1 +
>   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%)
>

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Paolo Bonzini]

On 16/05/2018 22:27, Maran Wilson wrote:
> 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.
> 
>    https://lkml.org/lkml/2018/4/16/1002

KVM bits look fine.  This would be the right time to post the QEMU
patches...

Paolo

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

On 5/18/2018 4:31 AM, Paolo Bonzini wrote:
> On 16/05/2018 22:27, Maran Wilson wrote:
>> 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.
>>
>>     https://lkml.org/lkml/2018/4/16/1002
> KVM bits look fine.  This would be the right time to post the QEMU
> patches...

Thanks Paolo. Yes, we will have the Qemu patches out soon. It is being 
actively worked. We have had one implementation in place, but decided to 
re-implement things slightly based on some preliminary feedback before 
sending it out to the wider community.

Thanks,
-Maran

> Paolo

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Paolo Bonzini]

On 17/04/18 01:09, 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:
> 
>    https://xenbits.xen.org/docs/unstable/misc/pvh.html
> 
> This patch series would enable Qemu to use that same entry point for
> booting KVM guests.

Hi Maran, what happened to this series (and to the QEMU work)?

Paolo

> 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: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH
>   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
> 
>  MAINTAINERS                                     |   1 +
>  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%)
> 

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Maran Wilson]

On 11/16/2018 2:46 AM, Paolo Bonzini wrote:
> On 17/04/18 01:09, 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:
>>
>>     https://xenbits.xen.org/docs/unstable/misc/pvh.html
>>
>> This patch series would enable Qemu to use that same entry point for
>> booting KVM guests.
> Hi Maran, what happened to this series (and to the QEMU work)?

Hi Paolo,

Thank you for the reminder. Sorry, I have been wanting to continue this 
work for a while now, but our team has been pulled in other directions 
and this one ended up getting temporarily pushed down the priority stack.

Let me discuss with my management and get back to you. I do want (and 
intend) to support and push this over the finish line.

In the meantime, if there are any folks out there with a specific 
business need for getting this done sooner rather than later and are 
able to invest a bit of time to collaborate on the remaining Qemu work, 
please feel free to ping me offline. We have some preliminary Qemu 
patches, but there is some additional work needed before they are ready 
wider review.

Thanks,
-Maran

>
> Paolo
>
>> 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: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH
>>    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
>>
>>   MAINTAINERS                                     |   1 +
>>   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%)
>>

Re: [PATCH v7 0/7] KVM: x86: Allow Qemu/KVM to use PVH entry point

[Paolo Bonzini]

On 16/11/18 18:17, Maran Wilson wrote:
> On 11/16/2018 2:46 AM, Paolo Bonzini wrote:
>> On 17/04/18 01:09, 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:
>>>
>>>     https://xenbits.xen.org/docs/unstable/misc/pvh.html
>>>
>>> This patch series would enable Qemu to use that same entry point for
>>> booting KVM guests.
>> Hi Maran, what happened to this series (and to the QEMU work)?
> 
> Hi Paolo,
> 
> Thank you for the reminder. Sorry, I have been wanting to continue this
> work for a while now, but our team has been pulled in other directions
> and this one ended up getting temporarily pushed down the priority stack.
> 
> Let me discuss with my management and get back to you. I do want (and
> intend) to support and push this over the finish line.
> 
> In the meantime, if there are any folks out there with a specific
> business need for getting this done sooner rather than later

Well, we are interested in using this to avoid the decompression cost of
booting a "container-like" VM image.  I'm not sure what we will do about
that, but certainly getting this included in the upstream projects would
be a prerequisite.

If you really prefer to discuss things offlist, feel free to include me,
Stefan and Stefano.

Paolo

> and are
> able to invest a bit of time to collaborate on the remaining Qemu work,
> please feel free to ping me offline. We have some preliminary Qemu
> patches, but there is some additional work needed before they are ready
> wider review.
> 
> Thanks,
> -Maran