Commit 819a63dc authored by Alexander Graf's avatar Alexander Graf Committed by Avi Kivity
Browse files

KVM: PPC: PV mtmsrd L=1 



The PowerPC ISA has a special instruction for mtmsr that only changes the EE
and RI bits, namely the L=1 form.

Since that one is reasonably often occuring and simple to implement, let's
go with this first. Writing EE=0 is always just a store. Doing EE=1 also
requires us to check for pending interrupts and if necessary exit back to the
hypervisor.

Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 92234722

arch/powerpc/kernel/kvm.c

+45 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ 
#define KVM_INST_MTSPR_DSISR	0x7c1203a6



#define KVM_INST_TLBSYNC	0x7c00046c

#define KVM_INST_MTMSRD_L1	0x7c010164



static bool kvm_patching_worked = true;

static char kvm_tmp[1024 * 1024];
@@ -138,6 +139,43 @@ static u32 *kvm_alloc(int len) 
	return p;

}



extern u32 kvm_emulate_mtmsrd_branch_offs;

extern u32 kvm_emulate_mtmsrd_reg_offs;

extern u32 kvm_emulate_mtmsrd_len;

extern u32 kvm_emulate_mtmsrd[];



static void kvm_patch_ins_mtmsrd(u32 *inst, u32 rt)

{

	u32 *p;

	int distance_start;

	int distance_end;

	ulong next_inst;



	p = kvm_alloc(kvm_emulate_mtmsrd_len * 4);

	if (!p)

		return;



	/* Find out where we are and put everything there */

	distance_start = (ulong)p - (ulong)inst;

	next_inst = ((ulong)inst + 4);

	distance_end = next_inst - (ulong)&p[kvm_emulate_mtmsrd_branch_offs];



	/* Make sure we only write valid b instructions */

	if (distance_start > KVM_INST_B_MAX) {

		kvm_patching_worked = false;

		return;

	}



	/* Modify the chunk to fit the invocation */

	memcpy(p, kvm_emulate_mtmsrd, kvm_emulate_mtmsrd_len * 4);

	p[kvm_emulate_mtmsrd_branch_offs] |= distance_end & KVM_INST_B_MASK;

	p[kvm_emulate_mtmsrd_reg_offs] |= rt;

	flush_icache_range((ulong)p, (ulong)p + kvm_emulate_mtmsrd_len * 4);



	/* Patch the invocation */

	kvm_patch_ins_b(inst, distance_start);

}



static void kvm_map_magic_page(void *data)

{

	kvm_hypercall2(KVM_HC_PPC_MAP_MAGIC_PAGE,
@@ -211,6 +249,13 @@ static void kvm_check_ins(u32 *inst) 
	case KVM_INST_TLBSYNC:

		kvm_patch_ins_nop(inst);

		break;



	/* Rewrites */

	case KVM_INST_MTMSRD_L1:

		/* We use r30 and r31 during the hook */

		if (get_rt(inst_rt) < 30)

			kvm_patch_ins_mtmsrd(inst, inst_rt);

		break;

	}



	switch (_inst) {

arch/powerpc/kernel/kvm_emul.S

+56 −0
Original line number Diff line number Diff line
@@ -64,3 +64,59 @@ kvm_hypercall_start: 
	/* Disable critical section. We are critical if			\

	   shared->critical == r1 and r2 is always != r1 */		\

	STL64(r2, KVM_MAGIC_PAGE + KVM_MAGIC_CRITICAL, 0);



.global kvm_emulate_mtmsrd

kvm_emulate_mtmsrd:



	SCRATCH_SAVE



	/* Put MSR & ~(MSR_EE|MSR_RI) in r31 */

	LL64(r31, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)

	lis	r30, (~(MSR_EE | MSR_RI))@h

	ori	r30, r30, (~(MSR_EE | MSR_RI))@l

	and	r31, r31, r30



	/* OR the register's (MSR_EE|MSR_RI) on MSR */

kvm_emulate_mtmsrd_reg:

	andi.	r30, r0, (MSR_EE|MSR_RI)

	or	r31, r31, r30



	/* Put MSR back into magic page */

	STL64(r31, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)



	/* Check if we have to fetch an interrupt */

	lwz	r31, (KVM_MAGIC_PAGE + KVM_MAGIC_INT)(0)

	cmpwi	r31, 0

	beq+	no_check



	/* Check if we may trigger an interrupt */

	andi.	r30, r30, MSR_EE

	beq	no_check



	SCRATCH_RESTORE



	/* Nag hypervisor */

	tlbsync



	b	kvm_emulate_mtmsrd_branch



no_check:



	SCRATCH_RESTORE



	/* Go back to caller */

kvm_emulate_mtmsrd_branch:

	b	.

kvm_emulate_mtmsrd_end:



.global kvm_emulate_mtmsrd_branch_offs

kvm_emulate_mtmsrd_branch_offs:

	.long (kvm_emulate_mtmsrd_branch - kvm_emulate_mtmsrd) / 4



.global kvm_emulate_mtmsrd_reg_offs

kvm_emulate_mtmsrd_reg_offs:

	.long (kvm_emulate_mtmsrd_reg - kvm_emulate_mtmsrd) / 4



.global kvm_emulate_mtmsrd_len

kvm_emulate_mtmsrd_len:

	.long (kvm_emulate_mtmsrd_end - kvm_emulate_mtmsrd) / 4

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