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Commit 1526bf9c authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Marcelo Tosatti
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KVM: s390: add capability indicating COW support 



Currently qemu/kvm on s390 uses a guest mapping that does not
allow the guest backing page table to be write-protected to
support older systems. On those older systems a host write
protection fault will be delivered to the guest.

Newer systems allow to write-protect the guest backing memory
and let the fault be delivered to the host, thus allowing COW.

Use a capability bit to tell qemu if that is possible.

Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent d8368af8

arch/s390/include/asm/sclp.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ int sclp_cpu_deconfigure(u8 cpu); 
void sclp_facilities_detect(void);

unsigned long long sclp_get_rnmax(void);

unsigned long long sclp_get_rzm(void);

u8 sclp_get_fac85(void);

int sclp_sdias_blk_count(void);

int sclp_sdias_copy(void *dest, int blk_num, int nr_blks);

int sclp_chp_configure(struct chp_id chpid);

arch/s390/kvm/kvm-s390.c

+4 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <asm/pgtable.h>

#include <asm/nmi.h>

#include <asm/switch_to.h>

#include <asm/sclp.h>

#include "kvm-s390.h"

#include "gaccess.h"
@@ -140,6 +141,9 @@ int kvm_dev_ioctl_check_extension(long ext) 
	case KVM_CAP_MAX_VCPUS:

		r = KVM_MAX_VCPUS;

		break;

	case KVM_CAP_S390_COW:

		r = sclp_get_fac85() & 0x2;

		break;

	default:

		r = 0;

	}

drivers/s390/char/sclp_cmd.c

+11 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/mm.h>

#include <linux/mmzone.h>

#include <linux/memory.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include <asm/chpid.h>

#include <asm/sclp.h>
@@ -38,7 +39,8 @@ struct read_info_sccb { 
	u64	facilities;		/* 48-55 */

	u8	_reserved2[84 - 56];	/* 56-83 */

	u8	fac84;			/* 84 */

	u8	_reserved3[91 - 85];	/* 85-90 */

	u8	fac85;			/* 85 */

	u8	_reserved3[91 - 86];	/* 86-90 */

	u8	flags;			/* 91 */

	u8	_reserved4[100 - 92];	/* 92-99 */

	u32	rnsize2;		/* 100-103 */
@@ -51,6 +53,7 @@ static int __initdata early_read_info_sccb_valid; 


u64 sclp_facilities;

static u8 sclp_fac84;

static u8 sclp_fac85;

static unsigned long long rzm;

static unsigned long long rnmax;
@@ -112,6 +115,7 @@ void __init sclp_facilities_detect(void) 
	sccb = &early_read_info_sccb;

	sclp_facilities = sccb->facilities;

	sclp_fac84 = sccb->fac84;

	sclp_fac85 = sccb->fac85;

	rnmax = sccb->rnmax ? sccb->rnmax : sccb->rnmax2;

	rzm = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;

	rzm <<= 20;
@@ -127,6 +131,12 @@ unsigned long long sclp_get_rzm(void) 
	return rzm;

}



u8 sclp_get_fac85(void)

{

	return sclp_fac85;

}

EXPORT_SYMBOL_GPL(sclp_get_fac85);



/*

 * This function will be called after sclp_facilities_detect(), which gets

 * called from early.c code. Therefore the sccb should have valid contents.

include/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -616,6 +616,7 @@ struct kvm_ppc_smmu_info { 
#define KVM_CAP_KVMCLOCK_CTRL 76

#define KVM_CAP_SIGNAL_MSI 77

#define KVM_CAP_PPC_GET_SMMU_INFO 78

#define KVM_CAP_S390_COW 79



#ifdef KVM_CAP_IRQ_ROUTING