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linux/arch/powerpc/kvm/book3s_64_interrupts.S
Alexander Graf 021ec9c69f KVM: PPC: Call SLB patching code in interrupt safe manner 
Currently we're racy when doing the transition from IR=1 to IR=0, from
the module memory entry code to the real mode SLB switching code.

To work around that I took a look at the RTAS entry code which is faced
with a similar problem and did the same thing:

  A small helper in linear mapped memory that does mtmsr with IR=0 and
  then RFIs info the actual handler.

Thanks to that trick we can safely take page faults in the entry code
and only need to be really wary of what to do as of the SLB switching
part.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
2010-03-01 12:35:49 -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>
*/
#include <asm/ppc_asm.h>
#include <asm/kvm_asm.h>
#include <asm/reg.h>
#include <asm/page.h>
#include <asm/asm-offsets.h>
#include <asm/exception-64s.h>
#define KVMPPC_HANDLE_EXIT .kvmppc_handle_exit
#define ULONG_SIZE 8
#define VCPU_GPR(n) (VCPU_GPRS + (n * ULONG_SIZE))
.macro DISABLE_INTERRUPTS
mfmsr r0
rldicl r0,r0,48,1
rotldi r0,r0,16
mtmsrd r0,1
.endm
#define VCPU_LOAD_NVGPRS(vcpu) \
ld r14, VCPU_GPR(r14)(vcpu); \
ld r15, VCPU_GPR(r15)(vcpu); \
ld r16, VCPU_GPR(r16)(vcpu); \
ld r17, VCPU_GPR(r17)(vcpu); \
ld r18, VCPU_GPR(r18)(vcpu); \
ld r19, VCPU_GPR(r19)(vcpu); \
ld r20, VCPU_GPR(r20)(vcpu); \
ld r21, VCPU_GPR(r21)(vcpu); \
ld r22, VCPU_GPR(r22)(vcpu); \
ld r23, VCPU_GPR(r23)(vcpu); \
ld r24, VCPU_GPR(r24)(vcpu); \
ld r25, VCPU_GPR(r25)(vcpu); \
ld r26, VCPU_GPR(r26)(vcpu); \
ld r27, VCPU_GPR(r27)(vcpu); \
ld r28, VCPU_GPR(r28)(vcpu); \
ld r29, VCPU_GPR(r29)(vcpu); \
ld r30, VCPU_GPR(r30)(vcpu); \
ld r31, VCPU_GPR(r31)(vcpu); \
/*****************************************************************************
* *
* Guest entry / exit code that is in kernel module memory (highmem) *
* *
****************************************************************************/
/* Registers:
* r3: kvm_run pointer
* r4: vcpu pointer
*/
_GLOBAL(__kvmppc_vcpu_entry)
kvm_start_entry:
/* Write correct stack frame */
mflr r0
std r0,16(r1)
/* Save host state to the stack */
stdu r1, -SWITCH_FRAME_SIZE(r1)
/* Save r3 (kvm_run) and r4 (vcpu) */
SAVE_2GPRS(3, r1)
/* Save non-volatile registers (r14 - r31) */
SAVE_NVGPRS(r1)
/* Save LR */
std r0, _LINK(r1)
/* Load non-volatile guest state from the vcpu */
VCPU_LOAD_NVGPRS(r4)
/* Save R1/R2 in the PACA */
std r1, PACA_KVM_HOST_R1(r13)
std r2, PACA_KVM_HOST_R2(r13)
/* XXX swap in/out on load? */
ld r3, VCPU_HIGHMEM_HANDLER(r4)
std r3, PACA_KVM_VMHANDLER(r13)
kvm_start_lightweight:
ld r9, VCPU_PC(r4) /* r9 = vcpu->arch.pc */
ld r10, VCPU_SHADOW_MSR(r4) /* r10 = vcpu->arch.shadow_msr */
/* Load some guest state in the respective registers */
ld r5, VCPU_CTR(r4) /* r5 = vcpu->arch.ctr */
/* will be swapped in by rmcall */
ld r3, VCPU_LR(r4) /* r3 = vcpu->arch.lr */
mtlr r3 /* LR = r3 */
DISABLE_INTERRUPTS
/* Some guests may need to have dcbz set to 32 byte length.
*
* Usually we ensure that by patching the guest's instructions
* to trap on dcbz and emulate it in the hypervisor.
*
* If we can, we should tell the CPU to use 32 byte dcbz though,
* because that's a lot faster.
*/
ld r3, VCPU_HFLAGS(r4)
rldicl. r3, r3, 0, 63 /* CR = ((r3 & 1) == 0) */
beq no_dcbz32_on
mfspr r3,SPRN_HID5
ori r3, r3, 0x80 /* XXX HID5_dcbz32 = 0x80 */
mtspr SPRN_HID5,r3
no_dcbz32_on:
ld r6, VCPU_RMCALL(r4)
mtctr r6
ld r3, VCPU_TRAMPOLINE_ENTER(r4)
LOAD_REG_IMMEDIATE(r4, MSR_KERNEL & ~(MSR_IR | MSR_DR))
/* Jump to SLB patching handlder and into our guest */
bctr
/*
* This is the handler in module memory. It gets jumped at from the
* lowmem trampoline code, so it's basically the guest exit code.
*
*/
.global kvmppc_handler_highmem
kvmppc_handler_highmem:
/*
* 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
* R13 = PACA
* PACA.KVM.* = guest *
*
*/
/* R7 = vcpu */
ld r7, GPR4(r1)
/* Now save the guest state */
stw r0, VCPU_LAST_INST(r7)
std r3, VCPU_PC(r7)
std r4, VCPU_SHADOW_MSR(r7)
std r5, VCPU_FAULT_DEAR(r7)
std r6, VCPU_FAULT_DSISR(r7)
ld r5, VCPU_HFLAGS(r7)
rldicl. r5, r5, 0, 63 /* CR = ((r5 & 1) == 0) */
beq no_dcbz32_off
mfspr r5,SPRN_HID5
rldimi r5,r5,6,56
mtspr SPRN_HID5,r5
no_dcbz32_off:
std r14, VCPU_GPR(r14)(r7)
std r15, VCPU_GPR(r15)(r7)
std r16, VCPU_GPR(r16)(r7)
std r17, VCPU_GPR(r17)(r7)
std r18, VCPU_GPR(r18)(r7)
std r19, VCPU_GPR(r19)(r7)
std r20, VCPU_GPR(r20)(r7)
std r21, VCPU_GPR(r21)(r7)
std r22, VCPU_GPR(r22)(r7)
std r23, VCPU_GPR(r23)(r7)
std r24, VCPU_GPR(r24)(r7)
std r25, VCPU_GPR(r25)(r7)
std r26, VCPU_GPR(r26)(r7)
std r27, VCPU_GPR(r27)(r7)
std r28, VCPU_GPR(r28)(r7)
std r29, VCPU_GPR(r29)(r7)
std r30, VCPU_GPR(r30)(r7)
std r31, VCPU_GPR(r31)(r7)
/* Save guest CTR */
mfctr r5
std r5, VCPU_CTR(r7)
/* Save guest LR */
mflr r5
std r5, VCPU_LR(r7)
/* Restore host msr -> SRR1 */
ld r6, VCPU_HOST_MSR(r7)
/*
* For some interrupts, we need to call the real Linux
* handler, so it can do work for us. This has to happen
* as if the interrupt arrived from the kernel though,
* so let's fake it here where most state is restored.
*
* Call Linux for hardware interrupts/decrementer
* r3 = address of interrupt handler (exit reason)
*/
cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL
beq call_linux_handler
cmpwi r12, BOOK3S_INTERRUPT_DECREMENTER
beq call_linux_handler
/* Back to EE=1 */
mtmsr r6
b kvm_return_point
call_linux_handler:
/*
* If we land here we need to jump back to the handler we
* came from.
*
* We have a page that we can access from real mode, so let's
* jump back to that and use it as a trampoline to get back into the
* interrupt handler!
*
* R3 still contains the exit code,
* R5 VCPU_HOST_RETIP and
* R6 VCPU_HOST_MSR
*/
/* Restore host IP -> SRR0 */
ld r5, VCPU_HOST_RETIP(r7)
/* XXX Better move to a safe function?
* What if we get an HTAB flush in between mtsrr0 and mtsrr1? */
mtlr r12
ld r4, VCPU_TRAMPOLINE_LOWMEM(r7)
mtsrr0 r4
LOAD_REG_IMMEDIATE(r3, MSR_KERNEL & ~(MSR_IR | MSR_DR))
mtsrr1 r3
RFI
.global kvm_return_point
kvm_return_point:
/* Jump back to lightweight entry if we're supposed to */
/* go back into the guest */
/* Pass the exit number as 3rd argument to kvmppc_handle_exit */
mr r5, r12
/* Restore r3 (kvm_run) and r4 (vcpu) */
REST_2GPRS(3, r1)
bl KVMPPC_HANDLE_EXIT
/* If RESUME_GUEST, get back in the loop */
cmpwi r3, RESUME_GUEST
beq kvm_loop_lightweight
cmpwi r3, RESUME_GUEST_NV
beq kvm_loop_heavyweight
kvm_exit_loop:
ld r4, _LINK(r1)
mtlr r4
/* Restore non-volatile host registers (r14 - r31) */
REST_NVGPRS(r1)
addi r1, r1, SWITCH_FRAME_SIZE
blr
kvm_loop_heavyweight:
ld r4, _LINK(r1)
std r4, (16 + SWITCH_FRAME_SIZE)(r1)
/* Load vcpu and cpu_run */
REST_2GPRS(3, r1)
/* Load non-volatile guest state from the vcpu */
VCPU_LOAD_NVGPRS(r4)
/* Jump back into the beginning of this function */
b kvm_start_lightweight
kvm_loop_lightweight:
/* We'll need the vcpu pointer */
REST_GPR(4, r1)
/* Jump back into the beginning of this function */
b kvm_start_lightweight
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