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linux/arch/powerpc/kvm/book3s_interrupts.S
Scott Wood 9d378dfac8 powerpc/booke64: Use SPRG7 for VDSO 
Previously SPRG3 was marked for use by both VDSO and critical
interrupts (though critical interrupts were not fully implemented).

In commit 8b64a9dfb0 ("powerpc/booke64:
Use SPRG0/3 scratch for bolted TLB miss & crit int"), Mihai Caraman
made an attempt to resolve this conflict by restoring the VDSO value
early in the critical interrupt, but this has some issues:

 - It's incompatible with EXCEPTION_COMMON which restores r13 from the
   by-then-overwritten scratch (this cost me some debugging time).
 - It forces critical exceptions to be a special case handled
   differently from even machine check and debug level exceptions.
 - It didn't occur to me that it was possible to make this work at all
   (by doing a final "ld r13, PACA_EXCRIT+EX_R13(r13)") until after
   I made (most of) this patch. :-)

It might be worth investigating using a load rather than SPRG on return
from all exceptions (except TLB misses where the scratch never leaves
the SPRG) -- it could save a few cycles.  Until then, let's stick with
SPRG for all exceptions.

Since we cannot use SPRG4-7 for scratch without corrupting the state of
a KVM guest, move VDSO to SPRG7 on book3e.  Since neither SPRG4-7 nor
critical interrupts exist on book3s, SPRG3 is still used for VDSO
there.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: kvm-ppc@vger.kernel.org
2014-03-19 19:57:14 -05:00

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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>
#if defined(CONFIG_PPC_BOOK3S_64)
#define FUNC(name) GLUE(.,name)
#define GET_SHADOW_VCPU(reg) addi reg, r13, PACA_SVCPU
#elif defined(CONFIG_PPC_BOOK3S_32)
#define FUNC(name) name
#define GET_SHADOW_VCPU(reg) lwz reg, (THREAD + THREAD_KVM_SVCPU)(r2)
#endif /* CONFIG_PPC_BOOK3S_XX */
#define VCPU_LOAD_NVGPRS(vcpu) \
PPC_LL r14, VCPU_GPR(R14)(vcpu); \
PPC_LL r15, VCPU_GPR(R15)(vcpu); \
PPC_LL r16, VCPU_GPR(R16)(vcpu); \
PPC_LL r17, VCPU_GPR(R17)(vcpu); \
PPC_LL r18, VCPU_GPR(R18)(vcpu); \
PPC_LL r19, VCPU_GPR(R19)(vcpu); \
PPC_LL r20, VCPU_GPR(R20)(vcpu); \
PPC_LL r21, VCPU_GPR(R21)(vcpu); \
PPC_LL r22, VCPU_GPR(R22)(vcpu); \
PPC_LL r23, VCPU_GPR(R23)(vcpu); \
PPC_LL r24, VCPU_GPR(R24)(vcpu); \
PPC_LL r25, VCPU_GPR(R25)(vcpu); \
PPC_LL r26, VCPU_GPR(R26)(vcpu); \
PPC_LL r27, VCPU_GPR(R27)(vcpu); \
PPC_LL r28, VCPU_GPR(R28)(vcpu); \
PPC_LL r29, VCPU_GPR(R29)(vcpu); \
PPC_LL r30, VCPU_GPR(R30)(vcpu); \
PPC_LL 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_run)
kvm_start_entry:
/* Write correct stack frame */
mflr r0
PPC_STL r0,PPC_LR_STKOFF(r1)
/* Save host state to the stack */
PPC_STLU 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 CR */
mfcr r14
stw r14, _CCR(r1)
/* Save LR */
PPC_STL r0, _LINK(r1)
/* Load non-volatile guest state from the vcpu */
VCPU_LOAD_NVGPRS(r4)
kvm_start_lightweight:
/* Copy registers into shadow vcpu so we can access them in real mode */
GET_SHADOW_VCPU(r3)
bl FUNC(kvmppc_copy_to_svcpu)
nop
REST_GPR(4, r1)
#ifdef CONFIG_PPC_BOOK3S_64
/* Get the dcbz32 flag */
PPC_LL r3, VCPU_HFLAGS(r4)
rldicl r3, r3, 0, 63 /* r3 &= 1 */
stb r3, HSTATE_RESTORE_HID5(r13)
/* Load up guest SPRG3 value, since it's user readable */
ld r3, VCPU_SHARED(r4)
ld r3, VCPU_SHARED_SPRG3(r3)
mtspr SPRN_SPRG3, r3
#endif /* CONFIG_PPC_BOOK3S_64 */
PPC_LL r4, VCPU_SHADOW_MSR(r4) /* get shadow_msr */
/* Jump to segment patching handler and into our guest */
bl FUNC(kvmppc_entry_trampoline)
nop
/*
* This is the handler in module memory. It gets jumped at from the
* lowmem trampoline code, so it's basically the guest exit code.
*
*/
/*
* Register usage at this point:
*
* R1 = host R1
* R2 = host R2
* R12 = exit handler id
* R13 = PACA
* SVCPU.* = guest *
* MSR.EE = 1
*
*/
PPC_LL r3, GPR4(r1) /* vcpu pointer */
/*
* kvmppc_copy_from_svcpu can clobber volatile registers, save
* the exit handler id to the vcpu and restore it from there later.
*/
stw r12, VCPU_TRAP(r3)
/* Transfer reg values from shadow vcpu back to vcpu struct */
/* On 64-bit, interrupts are still off at this point */
GET_SHADOW_VCPU(r4)
bl FUNC(kvmppc_copy_from_svcpu)
nop
#ifdef CONFIG_PPC_BOOK3S_64
/*
* Reload kernel SPRG3 value.
* No need to save guest value as usermode can't modify SPRG3.
*/
ld r3, PACA_SPRG_VDSO(r13)
mtspr SPRN_SPRG_VDSO_WRITE, r3
#endif /* CONFIG_PPC_BOOK3S_64 */
/* R7 = vcpu */
PPC_LL r7, GPR4(r1)
PPC_STL r14, VCPU_GPR(R14)(r7)
PPC_STL r15, VCPU_GPR(R15)(r7)
PPC_STL r16, VCPU_GPR(R16)(r7)
PPC_STL r17, VCPU_GPR(R17)(r7)
PPC_STL r18, VCPU_GPR(R18)(r7)
PPC_STL r19, VCPU_GPR(R19)(r7)
PPC_STL r20, VCPU_GPR(R20)(r7)
PPC_STL r21, VCPU_GPR(R21)(r7)
PPC_STL r22, VCPU_GPR(R22)(r7)
PPC_STL r23, VCPU_GPR(R23)(r7)
PPC_STL r24, VCPU_GPR(R24)(r7)
PPC_STL r25, VCPU_GPR(R25)(r7)
PPC_STL r26, VCPU_GPR(R26)(r7)
PPC_STL r27, VCPU_GPR(R27)(r7)
PPC_STL r28, VCPU_GPR(R28)(r7)
PPC_STL r29, VCPU_GPR(R29)(r7)
PPC_STL r30, VCPU_GPR(R30)(r7)
PPC_STL r31, VCPU_GPR(R31)(r7)
/* Pass the exit number as 3rd argument to kvmppc_handle_exit */
lwz r5, VCPU_TRAP(r7)
/* Restore r3 (kvm_run) and r4 (vcpu) */
REST_2GPRS(3, r1)
bl FUNC(kvmppc_handle_exit_pr)
/* 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:
PPC_LL r4, _LINK(r1)
mtlr r4
lwz r14, _CCR(r1)
mtcr r14
/* Restore non-volatile host registers (r14 - r31) */
REST_NVGPRS(r1)
addi r1, r1, SWITCH_FRAME_SIZE
blr
kvm_loop_heavyweight:
PPC_LL r4, _LINK(r1)
PPC_STL r4, (PPC_LR_STKOFF + 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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