Patchwork [3/7] target-arm: mark up cpregs for no-migrate or raw access

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Submitter Peter Maydell
Date May 17, 2013, 1:23 p.m.
Message ID <1368797037-26976-4-git-send-email-peter.maydell@linaro.org>
Download mbox | patch
Permalink /patch/244650/
State New
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Comments

Peter Maydell - May 17, 2013, 1:23 p.m.
Mark up coprocessor register definitions to add raw access
functions or mark the register as non-migratable where necessary.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/helper.c |   94 ++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 63 insertions(+), 31 deletions(-)
Christoffer Dall - May 30, 2013, 10:13 p.m.
On Fri, May 17, 2013 at 02:23:53PM +0100, Peter Maydell wrote:
> Mark up coprocessor register definitions to add raw access
> functions or mark the register as non-migratable where necessary.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target-arm/helper.c |   94 ++++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 63 insertions(+), 31 deletions(-)
> 
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 2585d59..e5e4ed2 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -155,13 +155,17 @@ static const ARMCPRegInfo cp_reginfo[] = {
>       * the unified TLB ops but also the dside/iside/inner-shareable variants.
>       */
>      { .name = "TLBIALL", .cp = 15, .crn = 8, .crm = CP_ANY,
> -      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W, .writefn = tlbiall_write, },
> +      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W, .writefn = tlbiall_write,
> +      .type = ARM_CP_NO_MIGRATE },

[...]

What happens with registers which don't have the raw_write function set
(even though the write function imposes some access checks or has side
effects) and also is not marked as ARM_CP_NO_MIGRATE, CONTEXTIDR seems
to be such an example. ?

-Christoffer
Peter Maydell - May 30, 2013, 10:27 p.m.
On 30 May 2013 23:13, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> What happens with registers which don't have the raw_write function set
> (even though the write function imposes some access checks or has side
> effects) and also is not marked as ARM_CP_NO_MIGRATE,

In the general case what happens is that we probably don't
sync (or migrate, for TCG) the register properly, because
we'll use the standard write function and get whatever it
does. (Note that mistakes in annotation don't affect KVM
migration because we always trust the kernel's register
list and values and work with them directly; we don't indirect
through the TCG CPUState structures to migrate the data.)

The alternative would seem to be to require a raw_read/write
function to be explicitly specified if there's a read/write
function (even if it's specified to be the same thing), but
that seemed to me like it would add a lot of boilerplate for
most register descriptions. Do you think it would be better
anyway, or do you have a better idea?

> CONTEXTIDR seems to be such an example. ?

In this specific case I decided it was safe to let the non-raw
write function do a tlb_flush(). Looking again that is kinda
expensive though, so we should probably mark these registers
up with raw_write functions.

thanks
-- PMM
Christoffer Dall - May 30, 2013, 10:38 p.m.
On Thu, May 30, 2013 at 11:27:01PM +0100, Peter Maydell wrote:
> On 30 May 2013 23:13, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> > What happens with registers which don't have the raw_write function set
> > (even though the write function imposes some access checks or has side
> > effects) and also is not marked as ARM_CP_NO_MIGRATE,
> 
> In the general case what happens is that we probably don't
> sync (or migrate, for TCG) the register properly, because
> we'll use the standard write function and get whatever it
> does. (Note that mistakes in annotation don't affect KVM
> migration because we always trust the kernel's register
> list and values and work with them directly; we don't indirect
> through the TCG CPUState structures to migrate the data.)
> 
> The alternative would seem to be to require a raw_read/write
> function to be explicitly specified if there's a read/write
> function (even if it's specified to be the same thing), but
> that seemed to me like it would add a lot of boilerplate for
> most register descriptions. Do you think it would be better
> anyway, or do you have a better idea?

Depends on how many places you add the raw functions.  I was thinking
about whether the absence of such a function could substitute the need
for the NO_MIGRATE flag, but, eh, there's probably other uses for having
that flag so it's not really preferred.

You probably did the best thing.

> 
> > CONTEXTIDR seems to be such an example. ?
> 
> In this specific case I decided it was safe to let the non-raw
> write function do a tlb_flush(). Looking again that is kinda
> expensive though, so we should probably mark these registers
> up with raw_write functions.
> 

Migration is sort of an expensive operation, so not sure if it's worth
it.

I am mostly worries about the case where we would miss raw read/write
functions and that could be hard to track down in the case where
migration fails, but I don't really have great suggestions on how to
ensure this.

-Christoffer
Peter Maydell - May 30, 2013, 10:42 p.m.
On 30 May 2013 23:38, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> On Thu, May 30, 2013 at 11:27:01PM +0100, Peter Maydell wrote:
>> On 30 May 2013 23:13, Christoffer Dall <christoffer.dall@linaro.org> wrote:
>> > CONTEXTIDR seems to be such an example. ?
>>
>> In this specific case I decided it was safe to let the non-raw
>> write function do a tlb_flush(). Looking again that is kinda
>> expensive though, so we should probably mark these registers
>> up with raw_write functions.
>>
>
> Migration is sort of an expensive operation, so not sure if it's worth
> it.

It'll also happen every time we drop out to a gdb attached
to the VM. But yes, this definitely isn't on any fast paths.

> I am mostly worries about the case where we would miss raw read/write
> functions and that could be hard to track down in the case where
> migration fails, but I don't really have great suggestions on how to
> ensure this.

That's the one argument for insisting on a raw function -- it
does mean that when looking at code and patches you can see
it's an explicit decision on how to handle the situation.

thanks
-- PMM

Patch

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 2585d59..e5e4ed2 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -155,13 +155,17 @@  static const ARMCPRegInfo cp_reginfo[] = {
      * the unified TLB ops but also the dside/iside/inner-shareable variants.
      */
     { .name = "TLBIALL", .cp = 15, .crn = 8, .crm = CP_ANY,
-      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W, .writefn = tlbiall_write, },
+      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W, .writefn = tlbiall_write,
+      .type = ARM_CP_NO_MIGRATE },
     { .name = "TLBIMVA", .cp = 15, .crn = 8, .crm = CP_ANY,
-      .opc1 = CP_ANY, .opc2 = 1, .access = PL1_W, .writefn = tlbimva_write, },
+      .opc1 = CP_ANY, .opc2 = 1, .access = PL1_W, .writefn = tlbimva_write,
+      .type = ARM_CP_NO_MIGRATE },
     { .name = "TLBIASID", .cp = 15, .crn = 8, .crm = CP_ANY,
-      .opc1 = CP_ANY, .opc2 = 2, .access = PL1_W, .writefn = tlbiasid_write, },
+      .opc1 = CP_ANY, .opc2 = 2, .access = PL1_W, .writefn = tlbiasid_write,
+      .type = ARM_CP_NO_MIGRATE },
     { .name = "TLBIMVAA", .cp = 15, .crn = 8, .crm = CP_ANY,
-      .opc1 = CP_ANY, .opc2 = 3, .access = PL1_W, .writefn = tlbimvaa_write, },
+      .opc1 = CP_ANY, .opc2 = 3, .access = PL1_W, .writefn = tlbimvaa_write,
+      .type = ARM_CP_NO_MIGRATE },
     /* Cache maintenance ops; some of this space may be overridden later. */
     { .name = "CACHEMAINT", .cp = 15, .crn = 7, .crm = CP_ANY,
       .opc1 = 0, .opc2 = CP_ANY, .access = PL1_W,
@@ -196,7 +200,8 @@  static const ARMCPRegInfo not_v7_cp_reginfo[] = {
       .resetvalue = 0 },
     /* v6 doesn't have the cache ID registers but Linux reads them anyway */
     { .name = "DUMMY", .cp = 15, .crn = 0, .crm = 0, .opc1 = 1, .opc2 = CP_ANY,
-      .access = PL1_R, .type = ARM_CP_CONST, .resetvalue = 0 },
+      .access = PL1_R, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = 0 },
     REGINFO_SENTINEL
 };
 
@@ -235,6 +240,21 @@  static const ARMCPRegInfo v6_cp_reginfo[] = {
     REGINFO_SENTINEL
 };
 
+
+static int raw_read(CPUARMState *env, const ARMCPRegInfo *ri,
+                    uint64_t *value)
+{
+    *value = CPREG_FIELD32(env, ri);
+    return 0;
+}
+
+static int raw_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                     uint64_t value)
+{
+    CPREG_FIELD32(env, ri) = value;
+    return 0;
+}
+
 static int pmreg_read(CPUARMState *env, const ARMCPRegInfo *ri,
                       uint64_t *value)
 {
@@ -366,13 +386,16 @@  static const ARMCPRegInfo v7_cp_reginfo[] = {
     { .name = "PMCNTENSET", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 1,
       .access = PL0_RW, .resetvalue = 0,
       .fieldoffset = offsetof(CPUARMState, cp15.c9_pmcnten),
-      .readfn = pmreg_read, .writefn = pmcntenset_write },
+      .readfn = pmreg_read, .writefn = pmcntenset_write,
+      .raw_readfn = raw_read, .raw_writefn = raw_write },
     { .name = "PMCNTENCLR", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 2,
       .access = PL0_RW, .fieldoffset = offsetof(CPUARMState, cp15.c9_pmcnten),
-      .readfn = pmreg_read, .writefn = pmcntenclr_write },
+      .readfn = pmreg_read, .writefn = pmcntenclr_write,
+      .type = ARM_CP_NO_MIGRATE },
     { .name = "PMOVSR", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 3,
       .access = PL0_RW, .fieldoffset = offsetof(CPUARMState, cp15.c9_pmovsr),
-      .readfn = pmreg_read, .writefn = pmovsr_write },
+      .readfn = pmreg_read, .writefn = pmovsr_write,
+      .raw_readfn = raw_read, .raw_writefn = raw_write },
     /* Unimplemented so WI. Strictly speaking write accesses in PL0 should
      * respect PMUSERENR.
      */
@@ -389,7 +412,8 @@  static const ARMCPRegInfo v7_cp_reginfo[] = {
     { .name = "PMXEVTYPER", .cp = 15, .crn = 9, .crm = 13, .opc1 = 0, .opc2 = 1,
       .access = PL0_RW,
       .fieldoffset = offsetof(CPUARMState, cp15.c9_pmxevtyper),
-      .readfn = pmreg_read, .writefn = pmxevtyper_write },
+      .readfn = pmreg_read, .writefn = pmxevtyper_write,
+      .raw_readfn = raw_read, .raw_writefn = raw_write },
     /* Unimplemented, RAZ/WI. XXX PMUSERENR */
     { .name = "PMXEVCNTR", .cp = 15, .crn = 9, .crm = 13, .opc1 = 0, .opc2 = 2,
       .access = PL0_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
@@ -397,22 +421,21 @@  static const ARMCPRegInfo v7_cp_reginfo[] = {
       .access = PL0_R | PL1_RW,
       .fieldoffset = offsetof(CPUARMState, cp15.c9_pmuserenr),
       .resetvalue = 0,
-      .writefn = pmuserenr_write },
+      .writefn = pmuserenr_write, .raw_writefn = raw_write },
     { .name = "PMINTENSET", .cp = 15, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 1,
       .access = PL1_RW,
       .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
       .resetvalue = 0,
-      .writefn = pmintenset_write },
+      .writefn = pmintenset_write, .raw_writefn = raw_write },
     { .name = "PMINTENCLR", .cp = 15, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 2,
-      .access = PL1_RW,
+      .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
       .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
-      .resetvalue = 0,
-      .writefn = pmintenclr_write },
+      .resetvalue = 0, .writefn = pmintenclr_write, },
     { .name = "SCR", .cp = 15, .crn = 1, .crm = 1, .opc1 = 0, .opc2 = 0,
       .access = PL1_RW, .fieldoffset = offsetof(CPUARMState, cp15.c1_scr),
       .resetvalue = 0, },
     { .name = "CCSIDR", .cp = 15, .crn = 0, .crm = 0, .opc1 = 1, .opc2 = 0,
-      .access = PL1_R, .readfn = ccsidr_read },
+      .access = PL1_R, .readfn = ccsidr_read, .type = ARM_CP_NO_MIGRATE },
     { .name = "CSSELR", .cp = 15, .crn = 0, .crm = 0, .opc1 = 2, .opc2 = 0,
       .access = PL1_RW, .fieldoffset = offsetof(CPUARMState, cp15.c0_cssel),
       .writefn = csselr_write, .resetvalue = 0 },
@@ -461,7 +484,7 @@  static const ARMCPRegInfo t2ee_cp_reginfo[] = {
       .writefn = teecr_write },
     { .name = "TEEHBR", .cp = 14, .crn = 1, .crm = 0, .opc1 = 6, .opc2 = 0,
       .access = PL0_RW, .fieldoffset = offsetof(CPUARMState, teehbr),
-      .resetvalue = 0,
+      .resetvalue = 0, .raw_readfn = raw_read, .raw_writefn = raw_write,
       .readfn = teehbr_read, .writefn = teehbr_write },
     REGINFO_SENTINEL
 };
@@ -486,7 +509,8 @@  static const ARMCPRegInfo generic_timer_cp_reginfo[] = {
     /* Dummy implementation: RAZ/WI the whole crn=14 space */
     { .name = "GENERIC_TIMER", .cp = 15, .crn = 14,
       .crm = CP_ANY, .opc1 = CP_ANY, .opc2 = CP_ANY,
-      .access = PL1_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
+      .access = PL1_RW, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = 0 },
     REGINFO_SENTINEL
 };
 
@@ -579,7 +603,7 @@  static const ARMCPRegInfo vapa_cp_reginfo[] = {
       .writefn = par_write },
 #ifndef CONFIG_USER_ONLY
     { .name = "ATS", .cp = 15, .crn = 7, .crm = 8, .opc1 = 0, .opc2 = CP_ANY,
-      .access = PL1_W, .writefn = ats_write },
+      .access = PL1_W, .writefn = ats_write, .type = ARM_CP_NO_MIGRATE },
 #endif
     REGINFO_SENTINEL
 };
@@ -664,11 +688,11 @@  static int arm946_prbs_write(CPUARMState *env, const ARMCPRegInfo *ri,
 
 static const ARMCPRegInfo pmsav5_cp_reginfo[] = {
     { .name = "DATA_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 0,
-      .access = PL1_RW,
+      .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
       .fieldoffset = offsetof(CPUARMState, cp15.c5_data), .resetvalue = 0,
       .readfn = pmsav5_data_ap_read, .writefn = pmsav5_data_ap_write, },
     { .name = "INSN_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 1,
-      .access = PL1_RW,
+      .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
       .fieldoffset = offsetof(CPUARMState, cp15.c5_insn), .resetvalue = 0,
       .readfn = pmsav5_insn_ap_read, .writefn = pmsav5_insn_ap_write, },
     { .name = "DATA_EXT_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 2,
@@ -801,6 +825,7 @@  static const ARMCPRegInfo omap_cp_reginfo[] = {
       .writefn = omap_threadid_write },
     { .name = "TI925T_STATUS", .cp = 15, .crn = 15,
       .crm = 8, .opc1 = 0, .opc2 = 0, .access = PL1_RW,
+      .type = ARM_CP_NO_MIGRATE,
       .readfn = arm_cp_read_zero, .writefn = omap_wfi_write, },
     /* TODO: Peripheral port remap register:
      * On OMAP2 mcr p15, 0, rn, c15, c2, 4 sets up the interrupt controller
@@ -808,7 +833,8 @@  static const ARMCPRegInfo omap_cp_reginfo[] = {
      * when MMU is off.
      */
     { .name = "OMAP_CACHEMAINT", .cp = 15, .crn = 7, .crm = CP_ANY,
-      .opc1 = 0, .opc2 = CP_ANY, .access = PL1_W, .type = ARM_CP_OVERRIDE,
+      .opc1 = 0, .opc2 = CP_ANY, .access = PL1_W,
+      .type = ARM_CP_OVERRIDE | ARM_CP_NO_MIGRATE,
       .writefn = omap_cachemaint_write },
     { .name = "C9", .cp = 15, .crn = 9,
       .crm = CP_ANY, .opc1 = CP_ANY, .opc2 = CP_ANY, .access = PL1_RW,
@@ -848,21 +874,24 @@  static const ARMCPRegInfo dummy_c15_cp_reginfo[] = {
      */
     { .name = "C15_IMPDEF", .cp = 15, .crn = 15,
       .crm = CP_ANY, .opc1 = CP_ANY, .opc2 = CP_ANY,
-      .access = PL1_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
+      .access = PL1_RW, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = 0 },
     REGINFO_SENTINEL
 };
 
 static const ARMCPRegInfo cache_dirty_status_cp_reginfo[] = {
     /* Cache status: RAZ because we have no cache so it's always clean */
     { .name = "CDSR", .cp = 15, .crn = 7, .crm = 10, .opc1 = 0, .opc2 = 6,
-      .access = PL1_R, .type = ARM_CP_CONST, .resetvalue = 0 },
+      .access = PL1_R, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = 0 },
     REGINFO_SENTINEL
 };
 
 static const ARMCPRegInfo cache_block_ops_cp_reginfo[] = {
     /* We never have a a block transfer operation in progress */
     { .name = "BXSR", .cp = 15, .crn = 7, .crm = 12, .opc1 = 0, .opc2 = 4,
-      .access = PL0_R, .type = ARM_CP_CONST, .resetvalue = 0 },
+      .access = PL0_R, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = 0 },
     /* The cache ops themselves: these all NOP for QEMU */
     { .name = "IICR", .cp = 15, .crm = 5, .opc1 = 0,
       .access = PL1_W, .type = ARM_CP_NOP|ARM_CP_64BIT },
@@ -884,9 +913,11 @@  static const ARMCPRegInfo cache_test_clean_cp_reginfo[] = {
      * to indicate that there are no dirty cache lines.
      */
     { .name = "TC_DCACHE", .cp = 15, .crn = 7, .crm = 10, .opc1 = 0, .opc2 = 3,
-      .access = PL0_R, .type = ARM_CP_CONST, .resetvalue = (1 << 30) },
+      .access = PL0_R, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = (1 << 30) },
     { .name = "TCI_DCACHE", .cp = 15, .crn = 7, .crm = 14, .opc1 = 0, .opc2 = 3,
-      .access = PL0_R, .type = ARM_CP_CONST, .resetvalue = (1 << 30) },
+      .access = PL0_R, .type = ARM_CP_CONST | ARM_CP_NO_MIGRATE,
+      .resetvalue = (1 << 30) },
     REGINFO_SENTINEL
 };
 
@@ -894,8 +925,8 @@  static const ARMCPRegInfo strongarm_cp_reginfo[] = {
     /* Ignore ReadBuffer accesses */
     { .name = "C9_READBUFFER", .cp = 15, .crn = 9,
       .crm = CP_ANY, .opc1 = CP_ANY, .opc2 = CP_ANY,
-      .access = PL1_RW, .type = ARM_CP_CONST | ARM_CP_OVERRIDE,
-      .resetvalue = 0 },
+      .access = PL1_RW, .resetvalue = 0,
+      .type = ARM_CP_CONST | ARM_CP_OVERRIDE | ARM_CP_NO_MIGRATE },
     REGINFO_SENTINEL
 };
 
@@ -921,7 +952,7 @@  static int mpidr_read(CPUARMState *env, const ARMCPRegInfo *ri,
 
 static const ARMCPRegInfo mpidr_cp_reginfo[] = {
     { .name = "MPIDR", .cp = 15, .crn = 0, .crm = 0, .opc1 = 0, .opc2 = 5,
-      .access = PL1_R, .readfn = mpidr_read },
+      .access = PL1_R, .readfn = mpidr_read, .type = ARM_CP_NO_MIGRATE },
     REGINFO_SENTINEL
 };
 
@@ -1104,7 +1135,8 @@  void register_cp_regs_for_features(ARMCPU *cpu)
             .name = "PMCR", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 0,
             .access = PL0_RW, .resetvalue = cpu->midr & 0xff000000,
             .fieldoffset = offsetof(CPUARMState, cp15.c9_pmcr),
-            .readfn = pmreg_read, .writefn = pmcr_write
+            .readfn = pmreg_read, .writefn = pmcr_write,
+            .raw_readfn = raw_read, .raw_writefn = raw_write,
         };
         ARMCPRegInfo clidr = {
             .name = "CLIDR", .cp = 15, .crn = 0, .crm = 0, .opc1 = 1, .opc2 = 1,
@@ -1176,7 +1208,7 @@  void register_cp_regs_for_features(ARMCPU *cpu)
             { .name = "MIDR",
               .cp = 15, .crn = 0, .crm = 0, .opc1 = 0, .opc2 = 0,
               .access = PL1_R, .resetvalue = cpu->midr,
-              .writefn = arm_cp_write_ignore,
+              .writefn = arm_cp_write_ignore, .raw_writefn = raw_write,
               .fieldoffset = offsetof(CPUARMState, cp15.c0_cpuid) },
             { .name = "CTR",
               .cp = 15, .crn = 0, .crm = 0, .opc1 = 0, .opc2 = 1,