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Commit 716ff017 authored by Maran Wilson's avatar Maran Wilson Committed by Boris Ostrovsky
Browse files

KVM: x86: Allow Qemu/KVM to use PVH entry point 

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: default avatarMaran Wilson <maran.wilson@oracle.com>
Suggested-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Suggested-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
parent d907be2b

arch/x86/Kbuild

+1 −1
Original line number Diff line number Diff line
@@ -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/

arch/x86/platform/pvh/Makefile

+2 −2
Original line number Diff line number Diff line 
# 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

arch/x86/platform/pvh/enlighten.c

+31 −11
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#include <asm/e820/api.h>

#include <asm/x86_init.h>



#include <asm/xen/interface.h>



#include <xen/xen.h>

#include <xen/interface/hvm/start_info.h>
@@ -40,11 +42,28 @@ 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));



	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 =
@@ -75,7 +94,7 @@ static void __init init_pvh_bootparams(void) 
	 * environment (i.e. hardware_subarch 0).

	 */

	pvh_bootparams.hdr.version = (2 << 8) | 12;

	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;

}
@@ -90,12 +109,9 @@ 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)

{

	if (xen_guest)

		xen_pvh_init();

}
@@ -105,13 +121,17 @@ 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);

}