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linux/arch/powerpc/kvm/book3s_64_slb.S
Alexander Graf b4433a7cce KVM: PPC: Implement 'skip instruction' mode 
To fetch the last instruction we were interrupted on, we enable DR in early
exit code, where we are still in a very transitional phase between guest
and host state.

Most of the time this seemed to work, but another CPU can easily flush our
TLB and HTAB which makes us go in the Linux page fault handler which totally
breaks because we still use the guest's SLB entries.

To work around that, let's introduce a second KVM guest mode that defines
that whenever we get a trap, we don't call the Linux handler or go into
the KVM exit code, but just jump over the faulting instruction.

That way a potentially bad lwz doesn't trigger any faults and we can later
on interpret the invalid instruction we fetched as "fetch didn't work".

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
2010-03-01 12:35:48 -03:00

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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* Copyright SUSE Linux Products GmbH 2009
*
* Authors: Alexander Graf <agraf@suse.de>
*/
#define SHADOW_SLB_ESID(num) (SLBSHADOW_SAVEAREA + (num * 0x10))
#define SHADOW_SLB_VSID(num) (SLBSHADOW_SAVEAREA + (num * 0x10) + 0x8)
#define UNBOLT_SLB_ENTRY(num) \
ld r9, SHADOW_SLB_ESID(num)(r12); \
/* Invalid? Skip. */; \
rldicl. r0, r9, 37, 63; \
beq slb_entry_skip_ ## num; \
xoris r9, r9, SLB_ESID_V@h; \
std r9, SHADOW_SLB_ESID(num)(r12); \
slb_entry_skip_ ## num:
#define REBOLT_SLB_ENTRY(num) \
ld r10, SHADOW_SLB_ESID(num)(r11); \
cmpdi r10, 0; \
beq slb_exit_skip_ ## num; \
oris r10, r10, SLB_ESID_V@h; \
ld r9, SHADOW_SLB_VSID(num)(r11); \
slbmte r9, r10; \
std r10, SHADOW_SLB_ESID(num)(r11); \
slb_exit_skip_ ## num:
/******************************************************************************
* *
* Entry code *
* *
*****************************************************************************/
.global kvmppc_handler_trampoline_enter
kvmppc_handler_trampoline_enter:
/* Required state:
*
* MSR = ~IR|DR
* R13 = PACA
* R1 = host R1
* R2 = host R2
* R9 = guest IP
* R10 = guest MSR
* all other GPRS = free
* PACA[KVM_CR] = guest CR
* PACA[KVM_XER] = guest XER
*/
mtsrr0 r9
mtsrr1 r10
/* Remove LPAR shadow entries */
#if SLB_NUM_BOLTED == 3
ld r12, PACA_SLBSHADOWPTR(r13)
/* Save off the first entry so we can slbie it later */
ld r10, SHADOW_SLB_ESID(0)(r12)
ld r11, SHADOW_SLB_VSID(0)(r12)
/* Remove bolted entries */
UNBOLT_SLB_ENTRY(0)
UNBOLT_SLB_ENTRY(1)
UNBOLT_SLB_ENTRY(2)
#else
#error unknown number of bolted entries
#endif
/* Flush SLB */
slbia
/* r0 = esid & ESID_MASK */
rldicr r10, r10, 0, 35
/* r0 |= CLASS_BIT(VSID) */
rldic r12, r11, 56 - 36, 36
or r10, r10, r12
slbie r10
isync
/* Fill SLB with our shadow */
lbz r12, PACA_KVM_SLB_MAX(r13)
mulli r12, r12, 16
addi r12, r12, PACA_KVM_SLB
add r12, r12, r13
/* for (r11 = kvm_slb; r11 < kvm_slb + kvm_slb_size; r11+=slb_entry) */
li r11, PACA_KVM_SLB
add r11, r11, r13
slb_loop_enter:
ld r10, 0(r11)
rldicl. r0, r10, 37, 63
beq slb_loop_enter_skip
ld r9, 8(r11)
slbmte r9, r10
slb_loop_enter_skip:
addi r11, r11, 16
cmpd cr0, r11, r12
blt slb_loop_enter
slb_do_enter:
/* Enter guest */
ld r0, (PACA_KVM_R0)(r13)
ld r1, (PACA_KVM_R1)(r13)
ld r2, (PACA_KVM_R2)(r13)
ld r3, (PACA_KVM_R3)(r13)
ld r4, (PACA_KVM_R4)(r13)
ld r5, (PACA_KVM_R5)(r13)
ld r6, (PACA_KVM_R6)(r13)
ld r7, (PACA_KVM_R7)(r13)
ld r8, (PACA_KVM_R8)(r13)
ld r9, (PACA_KVM_R9)(r13)
ld r10, (PACA_KVM_R10)(r13)
ld r12, (PACA_KVM_R12)(r13)
lwz r11, (PACA_KVM_CR)(r13)
mtcr r11
ld r11, (PACA_KVM_XER)(r13)
mtxer r11
ld r11, (PACA_KVM_R11)(r13)
ld r13, (PACA_KVM_R13)(r13)
RFI
kvmppc_handler_trampoline_enter_end:
/******************************************************************************
* *
* Exit code *
* *
*****************************************************************************/
.global kvmppc_handler_trampoline_exit
kvmppc_handler_trampoline_exit:
/* Register usage at this point:
*
* SPRG_SCRATCH0 = guest R13
* R12 = exit handler id
* R13 = PACA
* PACA.KVM.SCRATCH0 = guest R12
* PACA.KVM.SCRATCH1 = guest CR
*
*/
/* Save registers */
std r0, PACA_KVM_R0(r13)
std r1, PACA_KVM_R1(r13)
std r2, PACA_KVM_R2(r13)
std r3, PACA_KVM_R3(r13)
std r4, PACA_KVM_R4(r13)
std r5, PACA_KVM_R5(r13)
std r6, PACA_KVM_R6(r13)
std r7, PACA_KVM_R7(r13)
std r8, PACA_KVM_R8(r13)
std r9, PACA_KVM_R9(r13)
std r10, PACA_KVM_R10(r13)
std r11, PACA_KVM_R11(r13)
/* Restore R1/R2 so we can handle faults */
ld r1, PACA_KVM_HOST_R1(r13)
ld r2, PACA_KVM_HOST_R2(r13)
/* Save guest PC and MSR in GPRs */
mfsrr0 r3
mfsrr1 r4
/* Get scratch'ed off registers */
mfspr r9, SPRN_SPRG_SCRATCH0
std r9, PACA_KVM_R13(r13)
ld r8, PACA_KVM_SCRATCH0(r13)
std r8, PACA_KVM_R12(r13)
lwz r7, PACA_KVM_SCRATCH1(r13)
stw r7, PACA_KVM_CR(r13)
/* Save more register state */
mfxer r6
stw r6, PACA_KVM_XER(r13)
mfdar r5
mfdsisr r6
/*
* In order for us to easily get the last instruction,
* we got the #vmexit at, we exploit the fact that the
* virtual layout is still the same here, so we can just
* ld from the guest's PC address
*/
/* We only load the last instruction when it's safe */
cmpwi r12, BOOK3S_INTERRUPT_DATA_STORAGE
beq ld_last_inst
cmpwi r12, BOOK3S_INTERRUPT_PROGRAM
beq ld_last_inst
b no_ld_last_inst
ld_last_inst:
/* Save off the guest instruction we're at */
/* Set guest mode to 'jump over instruction' so if lwz faults
* we'll just continue at the next IP. */
li r9, KVM_GUEST_MODE_SKIP
stb r9, PACA_KVM_IN_GUEST(r13)
/* 1) enable paging for data */
mfmsr r9
ori r11, r9, MSR_DR /* Enable paging for data */
mtmsr r11
/* 2) fetch the instruction */
li r0, KVM_INST_FETCH_FAILED /* In case lwz faults */
lwz r0, 0(r3)
/* 3) disable paging again */
mtmsr r9
no_ld_last_inst:
/* Unset guest mode */
li r9, KVM_GUEST_MODE_NONE
stb r9, PACA_KVM_IN_GUEST(r13)
/* Restore bolted entries from the shadow and fix it along the way */
/* We don't store anything in entry 0, so we don't need to take care of it */
slbia
isync
#if SLB_NUM_BOLTED == 3
ld r11, PACA_SLBSHADOWPTR(r13)
REBOLT_SLB_ENTRY(0)
REBOLT_SLB_ENTRY(1)
REBOLT_SLB_ENTRY(2)
#else
#error unknown number of bolted entries
#endif
slb_do_exit:
/* Register usage at this point:
*
* R0 = guest last inst
* R1 = host R1
* R2 = host R2
* R3 = guest PC
* R4 = guest MSR
* R5 = guest DAR
* R6 = guest DSISR
* R12 = exit handler id
* R13 = PACA
* PACA.KVM.* = guest *
*
*/
/* RFI into the highmem handler */
mfmsr r7
ori r7, r7, MSR_IR|MSR_DR|MSR_RI /* Enable paging */
mtsrr1 r7
ld r8, PACA_KVM_VMHANDLER(r13) /* Highmem handler address */
mtsrr0 r8
RFI
kvmppc_handler_trampoline_exit_end:
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