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Commit 49b99e1e authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Gleb Natapov
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s390/kvm: Provide a way to prevent reentering SIE 



Lets provide functions to prevent KVM from reentering SIE and
to kick cpus out of SIE. We cannot use the common kvm_vcpu_kick code,
since we need to kick out guests in places that hold architecture
specific locks (e.g. pgste lock) which might be necessary on the
other cpus - so no waiting possible.

So lets provide a bit in a private field of the sie control block
that acts as a gate keeper, after we claimed we are in SIE.
Please note that we do not reuse prog0c, since we want to access
that bit without atomic ops.

Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent 95d38fd0

arch/s390/include/asm/kvm_host.h

+4 −1
Original line number Diff line number Diff line
@@ -71,7 +71,10 @@ struct kvm_s390_sie_block { 
	__u8	reserved08[4];		/* 0x0008 */

#define PROG_IN_SIE (1<<0)

	__u32	prog0c;			/* 0x000c */

	__u8	reserved10[24];		/* 0x0010 */

	__u8	reserved10[16];		/* 0x0010 */

#define PROG_BLOCK_SIE 0x00000001

	atomic_t prog20;		/* 0x0020 */

	__u8	reserved24[4];		/* 0x0024 */

	__u64	cputm;			/* 0x0028 */

	__u64	ckc;			/* 0x0030 */

	__u64	epoch;			/* 0x0038 */

arch/s390/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -163,6 +163,7 @@ int main(void) 
	DEFINE(__THREAD_trap_tdb, offsetof(struct task_struct, thread.trap_tdb));

	DEFINE(__GMAP_ASCE, offsetof(struct gmap, asce));

	DEFINE(__SIE_PROG0C, offsetof(struct kvm_s390_sie_block, prog0c));

	DEFINE(__SIE_PROG20, offsetof(struct kvm_s390_sie_block, prog20));

#endif /* CONFIG_32BIT */

	return 0;

}

arch/s390/kernel/entry64.S

+3 −1
Original line number Diff line number Diff line
@@ -958,7 +958,9 @@ sie_loop: 
	lctlg	%c1,%c1,__GMAP_ASCE(%r14)	# load primary asce

sie_gmap:

	lg	%r14,__SF_EMPTY(%r15)		# get control block pointer

	oi	__SIE_PROG0C+3(%r14),1		# we are in SIE now

	oi	__SIE_PROG0C+3(%r14),1		# we are going into SIE now

	tm	__SIE_PROG20+3(%r14),1		# last exit...

	jnz	sie_done

	LPP	__SF_EMPTY(%r15)		# set guest id

	sie	0(%r14)

sie_done:

arch/s390/kvm/kvm-s390.c

+28 −0
Original line number Diff line number Diff line
@@ -454,6 +454,34 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu) 
	return 0;

}



void s390_vcpu_block(struct kvm_vcpu *vcpu)

{

	atomic_set_mask(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);

}



void s390_vcpu_unblock(struct kvm_vcpu *vcpu)

{

	atomic_clear_mask(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);

}



/*

 * Kick a guest cpu out of SIE and wait until SIE is not running.

 * If the CPU is not running (e.g. waiting as idle) the function will

 * return immediately. */

void exit_sie(struct kvm_vcpu *vcpu)

{

	atomic_set_mask(CPUSTAT_STOP_INT, &vcpu->arch.sie_block->cpuflags);

	while (vcpu->arch.sie_block->prog0c & PROG_IN_SIE)

		cpu_relax();

}



/* Kick a guest cpu out of SIE and prevent SIE-reentry */

void exit_sie_sync(struct kvm_vcpu *vcpu)

{

	s390_vcpu_block(vcpu);

	exit_sie(vcpu);

}



int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)

{

	/* kvm common code refers to this, but never calls it */

arch/s390/kvm/kvm-s390.h

+4 −0
Original line number Diff line number Diff line
@@ -133,6 +133,10 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu); 
/* implemented in kvm-s390.c */

int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu,

				 unsigned long addr);

void s390_vcpu_block(struct kvm_vcpu *vcpu);

void s390_vcpu_unblock(struct kvm_vcpu *vcpu);

void exit_sie(struct kvm_vcpu *vcpu);

void exit_sie_sync(struct kvm_vcpu *vcpu);

/* implemented in diag.c */

int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);