[PATCH REPOST 1/5] ARM: kvm: replace push and pop with stdmb and ldmia instrs to enable assembler.h inclusion

Victor Kamensky victor.kamensky at linaro.org
Wed Jan 22 01:41:09 EST 2014


Russell, Dave, Will, could you please check below
inline, looking for your opinion.

Marc, response is inline.

On 21 January 2014 01:58, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On 21/01/14 01:18, Christoffer Dall wrote:
>> On Fri, Dec 20, 2013 at 08:48:41AM -0800, Victor Kamensky wrote:
>>> Before fix kvm interrupt.S and interrupt_head.S used push and pop assembler
>>> instruction. It causes problem if <asm/assembler.h> file should be include. In
>>> assembler.h "push" is defined as macro so it causes compilation errors like
>>> this:
>>
>> "Before fix kvm..." doesn't read very pleasently, consider using
>> something like "Prior to this commit...."
>>
>> "causes a problem" or "causes problems"
>>
>> change "if <asm/assembler.h> file should be include..." to "if
>> <asm/assembler.h> is included, because assember.h defines 'push' as a
>> macro..."
>>
>>
>>
>>>
>>> arch/arm/kvm/interrupts.S: Assembler messages:
>>> arch/arm/kvm/interrupts.S:51: Error: ARM register expected -- `lsr {r2,r3}'
>>>
>>> Solution implemented by this patch replaces all 'push {...}' with
>>> 'stdmb sp!, {...}' instruction; and all 'pop {...}' with 'ldmia sp!, {...}'.
>>>
>>> Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
>>> ---
>>>  arch/arm/kvm/interrupts.S      | 38 +++++++++++++++++++-------------------
>>>  arch/arm/kvm/interrupts_head.S | 34 +++++++++++++++++-----------------
>>>  2 files changed, 36 insertions(+), 36 deletions(-)
>>>
>>> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
>>> index ddc1553..df19133 100644
>>> --- a/arch/arm/kvm/interrupts.S
>>> +++ b/arch/arm/kvm/interrupts.S
>>> @@ -47,7 +47,7 @@ __kvm_hyp_code_start:
>>>   * instead, ignoring the ipa value.
>>>   */
>>>  ENTRY(__kvm_tlb_flush_vmid_ipa)
>>> -    push    {r2, r3}
>>> +    stmdb   sp!, {r2, r3}
>>>
>>>      dsb     ishst
>>>      add     r0, r0, #KVM_VTTBR
>>> @@ -62,7 +62,7 @@ ENTRY(__kvm_tlb_flush_vmid_ipa)
>>>      mcrr    p15, 6, r2, r3, c2      @ Back to VMID #0
>>>      isb                             @ Not necessary if followed by eret
>>>
>>> -    pop     {r2, r3}
>>> +    ldmia   sp!, {r2, r3}
>>>      bx      lr
>>>  ENDPROC(__kvm_tlb_flush_vmid_ipa)
>>>
>>> @@ -110,7 +110,7 @@ ENTRY(__kvm_vcpu_run)
>>>  #ifdef CONFIG_VFPv3
>>>      @ Set FPEXC_EN so the guest doesn't trap floating point instructions
>>>      VFPFMRX r2, FPEXC               @ VMRS
>>> -    push    {r2}
>>> +    stmdb   sp!, {r2}
>>>      orr     r2, r2, #FPEXC_EN
>>>      VFPFMXR FPEXC, r2               @ VMSR
>>>  #endif
>>> @@ -175,7 +175,7 @@ __kvm_vcpu_return:
>>>
>>>  after_vfp_restore:
>>>      @ Restore FPEXC_EN which we clobbered on entry
>>> -    pop     {r2}
>>> +    ldmia   sp!, {r2}
>>>      VFPFMXR FPEXC, r2
>>>  #endif
>>>
>>> @@ -260,7 +260,7 @@ ENTRY(kvm_call_hyp)
>>>
>>>  /* Handle undef, svc, pabt, or dabt by crashing with a user notice */
>>>  .macro bad_exception exception_code, panic_str
>>> -    push    {r0-r2}
>>> +    stmdb   sp!, {r0-r2}
>>>      mrrc    p15, 6, r0, r1, c2      @ Read VTTBR
>>>      lsr     r1, r1, #16
>>>      ands    r1, r1, #0xff
>>> @@ -338,7 +338,7 @@ hyp_hvc:
>>>       * Getting here is either becuase of a trap from a guest or from calling
>>>       * HVC from the host kernel, which means "switch to Hyp mode".
>>>       */
>>> -    push    {r0, r1, r2}
>>> +    stmdb   sp!, {r0, r1, r2}
>>>
>>>      @ Check syndrome register
>>>      mrc     p15, 4, r1, c5, c2, 0   @ HSR
>>> @@ -361,11 +361,11 @@ hyp_hvc:
>>>      bne     guest_trap              @ Guest called HVC
>>>
>>>  host_switch_to_hyp:
>>> -    pop     {r0, r1, r2}
>>> +    ldmia   sp!, {r0, r1, r2}
>>>
>>> -    push    {lr}
>>> +    stmdb   sp!, {lr}
>>>      mrs     lr, SPSR
>>> -    push    {lr}
>>> +    stmdb   sp!, {lr}
>>>
>>>      mov     lr, r0
>>>      mov     r0, r1
>>> @@ -375,9 +375,9 @@ host_switch_to_hyp:
>>>  THUMB(      orr     lr, #1)
>>>      blx     lr                      @ Call the HYP function
>>>
>>> -    pop     {lr}
>>> +    ldmia   sp!, {lr}
>>>      msr     SPSR_csxf, lr
>>> -    pop     {lr}
>>> +    ldmia   sp!, {lr}
>>>      eret
>>>
>>>  guest_trap:
>>> @@ -418,7 +418,7 @@ guest_trap:
>>>
>>>      /* Preserve PAR */
>>>      mrrc    p15, 0, r0, r1, c7      @ PAR
>>> -    push    {r0, r1}
>>> +    stmdb   sp!, {r0, r1}
>>>
>>>      /* Resolve IPA using the xFAR */
>>>      mcr     p15, 0, r2, c7, c8, 0   @ ATS1CPR
>>> @@ -431,7 +431,7 @@ guest_trap:
>>>      orr     r2, r2, r1, lsl #24
>>>
>>>      /* Restore PAR */
>>> -    pop     {r0, r1}
>>> +    ldmia   sp!, {r0, r1}
>>>      mcrr    p15, 0, r0, r1, c7      @ PAR
>>>
>>>  3:  load_vcpu                       @ Load VCPU pointer to r0
>>> @@ -440,10 +440,10 @@ guest_trap:
>>>  1:  mov     r1, #ARM_EXCEPTION_HVC
>>>      b       __kvm_vcpu_return
>>>
>>> -4:  pop     {r0, r1}                @ Failed translation, return to guest
>>> +4:  ldmia   sp!, {r0, r1}           @ Failed translation, return to guest
>>>      mcrr    p15, 0, r0, r1, c7      @ PAR
>>>      clrex
>>> -    pop     {r0, r1, r2}
>>> +    ldmia   sp!, {r0, r1, r2}
>>>      eret
>>>
>>>  /*
>>> @@ -455,7 +455,7 @@ guest_trap:
>>>  #ifdef CONFIG_VFPv3
>>>  switch_to_guest_vfp:
>>>      load_vcpu                       @ Load VCPU pointer to r0
>>> -    push    {r3-r7}
>>> +    stmdb   sp!, {r3-r7}
>>>
>>>      @ NEON/VFP used.  Turn on VFP access.
>>>      set_hcptr vmexit, (HCPTR_TCP(10) | HCPTR_TCP(11))
>>> @@ -467,15 +467,15 @@ switch_to_guest_vfp:
>>>      add     r7, r0, #VCPU_VFP_GUEST
>>>      restore_vfp_state r7
>>>
>>> -    pop     {r3-r7}
>>> -    pop     {r0-r2}
>>> +    ldmia   sp!, {r3-r7}
>>> +    ldmia   sp!, {r0-r2}
>>>      clrex
>>>      eret
>>>  #endif
>>>
>>>      .align
>>>  hyp_irq:
>>> -    push    {r0, r1, r2}
>>> +    stmdb   sp!, {r0, r1, r2}
>>>      mov     r1, #ARM_EXCEPTION_IRQ
>>>      load_vcpu                       @ Load VCPU pointer to r0
>>>      b       __kvm_vcpu_return
>>> diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
>>> index 6f18695..c371db7 100644
>>> --- a/arch/arm/kvm/interrupts_head.S
>>> +++ b/arch/arm/kvm/interrupts_head.S
>>> @@ -63,7 +63,7 @@ vcpu       .req    r0              @ vcpu pointer always in r0
>>>      mrs     r2, SP_\mode
>>>      mrs     r3, LR_\mode
>>>      mrs     r4, SPSR_\mode
>>> -    push    {r2, r3, r4}
>>> +    stmdb   sp!, {r2, r3, r4}
>>>  .endm
>>>
>>>  /*
>>> @@ -73,13 +73,13 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>  .macro save_host_regs
>>>      /* Hyp regs. Only ELR_hyp (SPSR_hyp already saved) */
>>>      mrs     r2, ELR_hyp
>>> -    push    {r2}
>>> +    stmdb   sp!, {r2}
>>>
>>>      /* usr regs */
>>> -    push    {r4-r12}        @ r0-r3 are always clobbered
>>> +    stmdb   sp!, {r4-r12}   @ r0-r3 are always clobbered
>>>      mrs     r2, SP_usr
>>>      mov     r3, lr
>>> -    push    {r2, r3}
>>> +    stmdb   sp!, {r2, r3}
>>>
>>>      push_host_regs_mode svc
>>>      push_host_regs_mode abt
>>> @@ -95,11 +95,11 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mrs     r7, SP_fiq
>>>      mrs     r8, LR_fiq
>>>      mrs     r9, SPSR_fiq
>>> -    push    {r2-r9}
>>> +    stmdb   sp!, {r2-r9}
>>>  .endm
>>>
>>>  .macro pop_host_regs_mode mode
>>> -    pop     {r2, r3, r4}
>>> +    ldmia   sp!, {r2, r3, r4}
>>>      msr     SP_\mode, r2
>>>      msr     LR_\mode, r3
>>>      msr     SPSR_\mode, r4
>>> @@ -110,7 +110,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>   * Clobbers all registers, in all modes, except r0 and r1.
>>>   */
>>>  .macro restore_host_regs
>>> -    pop     {r2-r9}
>>> +    ldmia   sp!, {r2-r9}
>>>      msr     r8_fiq, r2
>>>      msr     r9_fiq, r3
>>>      msr     r10_fiq, r4
>>> @@ -125,12 +125,12 @@ vcpu   .req    r0              @ vcpu pointer always in r0
>>>      pop_host_regs_mode abt
>>>      pop_host_regs_mode svc
>>>
>>> -    pop     {r2, r3}
>>> +    ldmia   sp!, {r2, r3}
>>>      msr     SP_usr, r2
>>>      mov     lr, r3
>>> -    pop     {r4-r12}
>>> +    ldmia   sp!, {r4-r12}
>>>
>>> -    pop     {r2}
>>> +    ldmia   sp!, {r2}
>>>      msr     ELR_hyp, r2
>>>  .endm
>>>
>>> @@ -218,7 +218,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      add     r2, vcpu, #VCPU_USR_REG(3)
>>>      stm     r2, {r3-r12}
>>>      add     r2, vcpu, #VCPU_USR_REG(0)
>>> -    pop     {r3, r4, r5}            @ r0, r1, r2
>>> +    ldmia   sp!, {r3, r4, r5}               @ r0, r1, r2
>>>      stm     r2, {r3, r4, r5}
>>>      mrs     r2, SP_usr
>>>      mov     r3, lr
>>> @@ -258,7 +258,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mrc     p15, 2, r12, c0, c0, 0  @ CSSELR
>>>
>>>      .if \store_to_vcpu == 0
>>> -    push    {r2-r12}                @ Push CP15 registers
>>> +    stmdb   sp!, {r2-r12}           @ Push CP15 registers
>>>      .else
>>>      str     r2, [vcpu, #CP15_OFFSET(c1_SCTLR)]
>>>      str     r3, [vcpu, #CP15_OFFSET(c1_CPACR)]
>>> @@ -286,7 +286,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mrc     p15, 0, r12, c12, c0, 0 @ VBAR
>>>
>>>      .if \store_to_vcpu == 0
>>> -    push    {r2-r12}                @ Push CP15 registers
>>> +    stmdb   sp!, {r2-r12}           @ Push CP15 registers
>>>      .else
>>>      str     r2, [vcpu, #CP15_OFFSET(c13_CID)]
>>>      str     r3, [vcpu, #CP15_OFFSET(c13_TID_URW)]
>>> @@ -305,7 +305,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mrrc    p15, 0, r4, r5, c7      @ PAR
>>>
>>>      .if \store_to_vcpu == 0
>>> -    push    {r2,r4-r5}
>>> +    stmdb   sp!, {r2,r4-r5}
>>>      .else
>>>      str     r2, [vcpu, #CP15_OFFSET(c14_CNTKCTL)]
>>>      add     r12, vcpu, #CP15_OFFSET(c7_PAR)
>>> @@ -322,7 +322,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>   */
>>>  .macro write_cp15_state read_from_vcpu
>>>      .if \read_from_vcpu == 0
>>> -    pop     {r2,r4-r5}
>>> +    ldmia   sp!, {r2,r4-r5}
>>>      .else
>>>      ldr     r2, [vcpu, #CP15_OFFSET(c14_CNTKCTL)]
>>>      add     r12, vcpu, #CP15_OFFSET(c7_PAR)
>>> @@ -333,7 +333,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mcrr    p15, 0, r4, r5, c7      @ PAR
>>>
>>>      .if \read_from_vcpu == 0
>>> -    pop     {r2-r12}
>>> +    ldmia   sp!, {r2-r12}
>>>      .else
>>>      ldr     r2, [vcpu, #CP15_OFFSET(c13_CID)]
>>>      ldr     r3, [vcpu, #CP15_OFFSET(c13_TID_URW)]
>>> @@ -361,7 +361,7 @@ vcpu     .req    r0              @ vcpu pointer always in r0
>>>      mcr     p15, 0, r12, c12, c0, 0 @ VBAR
>>>
>>>      .if \read_from_vcpu == 0
>>> -    pop     {r2-r12}
>>> +    ldmia   sp!, {r2-r12}
>>>      .else
>>>      ldr     r2, [vcpu, #CP15_OFFSET(c1_SCTLR)]
>>>      ldr     r3, [vcpu, #CP15_OFFSET(c1_CPACR)]
>>> --
>>> 1.8.1.4
>>>
>>
>> If you fix to address Dave's comments, then the code change otherwise
>> looks good.
>
> How about trying this alternative approach:
>
> It looks like all the users of the push/pop macros are located in
> arch/arm/lib (mostly checksumming code). Can't we move these macros to a
> separate include file and leave the code that uses push/pop (as defined
> by the assembler) alone?

Marc, personally I am OK with such proposal. I was considering something
along these lines as one of the options. It works for me both ways. If
others agree I am happy to recode it as your suggested. I choose
proposed above patch because kvm arm code came after push and pop
defines were introduced in asm/assembler.h and used in other places.
I am OK either way. I agree that use of push and pop as define names
seems a bit unfortunate, but I don't have any historic visibility here

Russell, Dave, Will, do you have any opinion on Marc's proposal to
fix this issue?

Thanks,
Victor


> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...



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