Commit 78109277 authored by Alexander Graf's avatar Alexander Graf Committed by Avi Kivity
Browse files

KVM: PPC: PV mtmsrd L=0 and mtmsr 



There is also a form of mtmsr where all bits need to be addressed. While the
PPC64 Linux kernel behaves resonably well here, on PPC32 we do not have an
L=1 form. It does mtmsr even for simple things like only changing EE.

So we need to hook into that one as well and check for a mask of bits that we
deem safe to change from within guest context.

Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 819a63dc

arch/powerpc/kernel/kvm.c

+51 −0
Original line number Diff line number Diff line
@@ -63,7 +63,9 @@ 
#define KVM_INST_MTSPR_DSISR	0x7c1203a6



#define KVM_INST_TLBSYNC	0x7c00046c

#define KVM_INST_MTMSRD_L0	0x7c000164

#define KVM_INST_MTMSRD_L1	0x7c010164

#define KVM_INST_MTMSR		0x7c000124



static bool kvm_patching_worked = true;

static char kvm_tmp[1024 * 1024];
@@ -176,6 +178,49 @@ static void kvm_patch_ins_mtmsrd(u32 *inst, u32 rt) 
	kvm_patch_ins_b(inst, distance_start);

}



extern u32 kvm_emulate_mtmsr_branch_offs;

extern u32 kvm_emulate_mtmsr_reg1_offs;

extern u32 kvm_emulate_mtmsr_reg2_offs;

extern u32 kvm_emulate_mtmsr_reg3_offs;

extern u32 kvm_emulate_mtmsr_orig_ins_offs;

extern u32 kvm_emulate_mtmsr_len;

extern u32 kvm_emulate_mtmsr[];



static void kvm_patch_ins_mtmsr(u32 *inst, u32 rt)

{

	u32 *p;

	int distance_start;

	int distance_end;

	ulong next_inst;



	p = kvm_alloc(kvm_emulate_mtmsr_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_mtmsr_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_mtmsr, kvm_emulate_mtmsr_len * 4);

	p[kvm_emulate_mtmsr_branch_offs] |= distance_end & KVM_INST_B_MASK;

	p[kvm_emulate_mtmsr_reg1_offs] |= rt;

	p[kvm_emulate_mtmsr_reg2_offs] |= rt;

	p[kvm_emulate_mtmsr_reg3_offs] |= rt;

	p[kvm_emulate_mtmsr_orig_ins_offs] = *inst;

	flush_icache_range((ulong)p, (ulong)p + kvm_emulate_mtmsr_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,
@@ -256,6 +301,12 @@ static void kvm_check_ins(u32 *inst) 
		if (get_rt(inst_rt) < 30)

			kvm_patch_ins_mtmsrd(inst, inst_rt);

		break;

	case KVM_INST_MTMSR:

	case KVM_INST_MTMSRD_L0:

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

		if (get_rt(inst_rt) < 30)

			kvm_patch_ins_mtmsr(inst, inst_rt);

		break;

	}



	switch (_inst) {

arch/powerpc/kernel/kvm_emul.S

+84 −0
Original line number Diff line number Diff line
@@ -120,3 +120,87 @@ kvm_emulate_mtmsrd_reg_offs: 
.global kvm_emulate_mtmsrd_len

kvm_emulate_mtmsrd_len:

	.long (kvm_emulate_mtmsrd_end - kvm_emulate_mtmsrd) / 4





#define MSR_SAFE_BITS (MSR_EE | MSR_CE | MSR_ME | MSR_RI)

#define MSR_CRITICAL_BITS ~MSR_SAFE_BITS



.global kvm_emulate_mtmsr

kvm_emulate_mtmsr:



	SCRATCH_SAVE



	/* Fetch old MSR in r31 */

	LL64(r31, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)



	/* Find the changed bits between old and new MSR */

kvm_emulate_mtmsr_reg1:

	xor	r31, r0, r31



	/* Check if we need to really do mtmsr */

	LOAD_REG_IMMEDIATE(r30, MSR_CRITICAL_BITS)

	and.	r31, r31, r30



	/* No critical bits changed? Maybe we can stay in the guest. */

	beq	maybe_stay_in_guest



do_mtmsr:



	SCRATCH_RESTORE



	/* Just fire off the mtmsr if it's critical */

kvm_emulate_mtmsr_orig_ins:

	mtmsr	r0



	b	kvm_emulate_mtmsr_branch



maybe_stay_in_guest:



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

	lwz	r31, (KVM_MAGIC_PAGE + KVM_MAGIC_INT)(0)

	cmpwi	r31, 0

	beq+	no_mtmsr



	/* Check if we may trigger an interrupt */

kvm_emulate_mtmsr_reg2:

	andi.	r31, r0, MSR_EE

	beq	no_mtmsr



	b	do_mtmsr



no_mtmsr:



	/* Put MSR into magic page because we don't call mtmsr */

kvm_emulate_mtmsr_reg3:

	STL64(r0, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)



	SCRATCH_RESTORE



	/* Go back to caller */

kvm_emulate_mtmsr_branch:

	b	.

kvm_emulate_mtmsr_end:



.global kvm_emulate_mtmsr_branch_offs

kvm_emulate_mtmsr_branch_offs:

	.long (kvm_emulate_mtmsr_branch - kvm_emulate_mtmsr) / 4



.global kvm_emulate_mtmsr_reg1_offs

kvm_emulate_mtmsr_reg1_offs:

	.long (kvm_emulate_mtmsr_reg1 - kvm_emulate_mtmsr) / 4



.global kvm_emulate_mtmsr_reg2_offs

kvm_emulate_mtmsr_reg2_offs:

	.long (kvm_emulate_mtmsr_reg2 - kvm_emulate_mtmsr) / 4



.global kvm_emulate_mtmsr_reg3_offs

kvm_emulate_mtmsr_reg3_offs:

	.long (kvm_emulate_mtmsr_reg3 - kvm_emulate_mtmsr) / 4



.global kvm_emulate_mtmsr_orig_ins_offs

kvm_emulate_mtmsr_orig_ins_offs:

	.long (kvm_emulate_mtmsr_orig_ins - kvm_emulate_mtmsr) / 4



.global kvm_emulate_mtmsr_len

kvm_emulate_mtmsr_len:

	.long (kvm_emulate_mtmsr_end - kvm_emulate_mtmsr) / 4

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