[Qemu-devel] [RFC PATCH 0/2] ppc/spapr: Fix migration of radix guests

[Qemu-devel] [RFC PATCH 0/2] ppc/spapr: Fix migration of radix guests

[Bharata B Rao]

Migrating radix guests fails with the following error on the target
side:

qemu-system-ppc64: htab_load() bad index 2113929216 (5378+0 entries) in htab stream (htab_shift=0)
qemu-system-ppc64: error while loading state for instance 0x0 of device 'spapr/htab'
qemu-system-ppc64: load of migration failed: Invalid argument 

Fix this by not registering htab savevm handler for radix case.

Patches apply against ppc-for-2.10 branch of dwg's tree.

Bharata B Rao (2):
  spapr: Make h_register_process_table hcall flags global
  spapr: Fix migration of Radix guests

 hw/ppc/spapr.c         | 18 +++++++++++++++---
 hw/ppc/spapr_hcall.c   | 36 +++++++++++++++++++-----------------
 include/hw/ppc/spapr.h | 13 +++++++++++++
 3 files changed, 47 insertions(+), 20 deletions(-)

-- 
2.7.4

[Qemu-devel] [RFC PATCH 1/2] spapr: Make h_register_process_table hcall flags global

[Bharata B Rao]

The flags used in h_register_process_table hcall are needed in spapr.c
and hence move them to a header file. While doing so, give them
slightly specific names.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
 hw/ppc/spapr_hcall.c   | 31 ++++++++++++++-----------------
 include/hw/ppc/spapr.h | 10 ++++++++++
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 0d608d6..3600b0e 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -924,13 +924,6 @@ static void spapr_check_setup_free_hpt(sPAPRMachineState *spapr,
     return;
 }
 
-#define FLAGS_MASK              0x01FULL
-#define FLAG_MODIFY             0x10
-#define FLAG_REGISTER           0x08
-#define FLAG_RADIX              0x04
-#define FLAG_HASH_PROC_TBL      0x02
-#define FLAG_GTSE               0x01
-
 static target_ulong h_register_process_table(PowerPCCPU *cpu,
                                              sPAPRMachineState *spapr,
                                              target_ulong opcode,
@@ -943,12 +936,13 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
     target_ulong table_size = args[3];
     uint64_t cproc;
 
-    if (flags & ~FLAGS_MASK) { /* Check no reserved bits are set */
+    if (flags & ~SPAPR_PROC_TABLE_MASK) { /* Check no reserved bits are set */
         return H_PARAMETER;
     }
-    if (flags & FLAG_MODIFY) {
-        if (flags & FLAG_REGISTER) {
-            if (flags & FLAG_RADIX) { /* Register new RADIX process table */
+    if (flags & SPAPR_PROC_TABLE_MODIFY) {
+        if (flags & SPAPR_PROC_TABLE_REGISTER) {
+            if (flags & SPAPR_PROC_TABLE_RADIX) {
+                /* Register new RADIX process table */
                 if (proc_tbl & 0xfff || proc_tbl >> 60) {
                     return H_P2;
                 } else if (page_size) {
@@ -958,7 +952,8 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
                 }
                 cproc = PATBE1_GR | proc_tbl | table_size;
             } else { /* Register new HPT process table */
-                if (flags & FLAG_HASH_PROC_TBL) { /* Hash with Segment Tables */
+                if (flags & SPAPR_PROC_TABLE_HPT_PT) {
+                    /* Hash with Segment Tables */
                     /* TODO - Not Supported */
                     /* Technically caused by flag bits => H_PARAMETER */
                     return H_PARAMETER;
@@ -981,7 +976,8 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
             cproc = spapr->patb_entry & PATBE1_GR;
         }
     } else { /* Maintain current registration */
-        if (!(flags & FLAG_RADIX) != !(spapr->patb_entry & PATBE1_GR)) {
+        if (!(flags & SPAPR_PROC_TABLE_RADIX) !=
+            !(spapr->patb_entry & PATBE1_GR)) {
             /* Technically caused by flag bits => H_PARAMETER */
             return H_PARAMETER; /* Existing Process Table Mismatch */
         }
@@ -996,13 +992,14 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
     /* Update the UPRT and GTSE bits in the LPCR for all cpus */
     CPU_FOREACH(cs) {
         set_spr(cs, SPR_LPCR, LPCR_UPRT | LPCR_GTSE,
-                ((flags & (FLAG_RADIX | FLAG_HASH_PROC_TBL)) ? LPCR_UPRT : 0) |
-                ((flags & FLAG_GTSE) ? LPCR_GTSE : 0));
+                ((flags & (SPAPR_PROC_TABLE_RADIX | SPAPR_PROC_TABLE_HPT_PT)) ?
+                LPCR_UPRT : 0) | ((flags & SPAPR_PROC_TABLE_GTSE) ?
+                SPAPR_PROC_TABLE_GTSE : 0));
     }
 
     if (kvm_enabled()) {
-        return kvmppc_configure_v3_mmu(cpu, flags & FLAG_RADIX,
-                                       flags & FLAG_GTSE, cproc);
+        return kvmppc_configure_v3_mmu(cpu, flags & SPAPR_PROC_TABLE_RADIX,
+                                       flags & SPAPR_PROC_TABLE_GTSE, cproc);
     }
     return H_SUCCESS;
 }
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 5802f88..a692e63 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -681,4 +681,14 @@ int spapr_rng_populate_dt(void *fdt);
 
 void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
 
+/*
+ * Defines for flag value used in H_REGISTER_PROC_TBL hcall.
+ */
+#define SPAPR_PROC_TABLE_MASK        0x01FULL
+#define SPAPR_PROC_TABLE_MODIFY      0x10
+#define SPAPR_PROC_TABLE_REGISTER    0x08
+#define SPAPR_PROC_TABLE_RADIX       0x04
+#define SPAPR_PROC_TABLE_HPT_PT      0x02
+#define SPAPR_PROC_TABLE_GTSE        0x01
+
 #endif /* HW_SPAPR_H */
-- 
2.7.4

[Qemu-devel] [RFC PATCH 2/2] spapr: Fix migration of Radix guests

[Bharata B Rao]

Currently HTAB savevm handlers get registered by default and migration
of radix guest will fail.

- Ensure that HTAB savevm handlers are not registered for radix case.
- Ensure that we issue KVM_PPC_CONFIGURE_V3_MMU for radix case post
  migration.

TODO: Right now I have delayed the HTAB savevm handler registration
to CAS call where we know if the guest is radix or hash. Another approach
is to let the HTAB handlers to be registered by default (as it is being
done currently, but unregister them from CAS when we discover radix
capability).

Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
 hw/ppc/spapr.c         | 18 +++++++++++++++---
 hw/ppc/spapr_hcall.c   |  5 +++++
 include/hw/ppc/spapr.h |  3 +++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e2dc77c..e14f55c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1436,6 +1436,14 @@ static int spapr_post_load(void *opaque, int version_id)
         err = spapr_rtc_import_offset(&spapr->rtc, spapr->rtc_offset);
     }
 
+    if (spapr->patb_entry && (spapr->patb_flags & SPAPR_PROC_TABLE_RADIX) &&
+        kvmppc_has_cap_mmu_radix() && kvm_enabled()) {
+        err = kvmppc_configure_v3_mmu(POWERPC_CPU(first_cpu),
+                                      spapr->patb_flags &
+                                      SPAPR_PROC_TABLE_RADIX,
+                                      spapr->patb_flags & SPAPR_PROC_TABLE_GTSE,
+                                      spapr->patb_entry);
+    }
     return err;
 }
 
@@ -1520,6 +1528,7 @@ static const VMStateDescription vmstate_spapr_patb_entry = {
     .needed = spapr_patb_entry_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT64(patb_entry, sPAPRMachineState),
+        VMSTATE_UINT64(patb_flags, sPAPRMachineState),
         VMSTATE_END_OF_LIST()
     },
 };
@@ -1869,6 +1878,12 @@ static SaveVMHandlers savevm_htab_handlers = {
     .load_state = htab_load,
 };
 
+void spapr_htab_savevm_register(sPAPRMachineState *spapr)
+{
+    register_savevm_live(NULL, "spapr/htab", -1, 1,
+                         &savevm_htab_handlers, spapr);
+}
+
 static void spapr_boot_set(void *opaque, const char *boot_device,
                            Error **errp)
 {
@@ -2331,9 +2346,6 @@ static void ppc_spapr_init(MachineState *machine)
      * interface, this is a legacy from the sPAPREnvironment structure
      * which predated MachineState but had a similar function */
     vmstate_register(NULL, 0, &vmstate_spapr, spapr);
-    register_savevm_live(NULL, "spapr/htab", -1, 1,
-                         &savevm_htab_handlers, spapr);
-
     /* used by RTAS */
     QTAILQ_INIT(&spapr->ccs_list);
     qemu_register_reset(spapr_ccs_reset_hook, spapr);
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 3600b0e..fa03ca0 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -988,6 +988,7 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
     spapr_check_setup_free_hpt(spapr, spapr->patb_entry, cproc);
 
     spapr->patb_entry = cproc; /* Save new process table */
+    spapr->patb_flags = flags; /* Save the flags */
 
     /* Update the UPRT and GTSE bits in the LPCR for all cpus */
     CPU_FOREACH(cs) {
@@ -1169,6 +1170,10 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
         }
     }
 
+    /* Register savevm handlers for HTAB case */
+    if (!guest_radix || !kvmppc_has_cap_mmu_radix()) {
+        spapr_htab_savevm_register(spapr);
+    }
     return H_SUCCESS;
 }
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index a692e63..0d0e9e4 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -75,6 +75,7 @@ struct sPAPRMachineState {
     void *htab;
     uint32_t htab_shift;
     uint64_t patb_entry; /* Process tbl registed in H_REGISTER_PROCESS_TABLE */
+    uint64_t patb_flags;
     hwaddr rma_size;
     int vrma_adjust;
     ssize_t rtas_size;
@@ -691,4 +692,6 @@ void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
 #define SPAPR_PROC_TABLE_HPT_PT      0x02
 #define SPAPR_PROC_TABLE_GTSE        0x01
 
+void spapr_htab_savevm_register(sPAPRMachineState *spapr);
+
 #endif /* HW_SPAPR_H */
-- 
2.7.4

Re: [Qemu-devel] [RFC PATCH 1/2] spapr: Make h_register_process_table hcall flags global

[David Gibson]

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On Mon, May 08, 2017 at 02:36:16PM +0530, Bharata B Rao wrote:
> The flags used in h_register_process_table hcall are needed in spapr.c
> and hence move them to a header file. While doing so, give them
> slightly specific names.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  hw/ppc/spapr_hcall.c   | 31 ++++++++++++++-----------------
>  include/hw/ppc/spapr.h | 10 ++++++++++
>  2 files changed, 24 insertions(+), 17 deletions(-)
> 
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 0d608d6..3600b0e 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -924,13 +924,6 @@ static void spapr_check_setup_free_hpt(sPAPRMachineState *spapr,
>      return;
>  }
>  
> -#define FLAGS_MASK              0x01FULL
> -#define FLAG_MODIFY             0x10
> -#define FLAG_REGISTER           0x08
> -#define FLAG_RADIX              0x04
> -#define FLAG_HASH_PROC_TBL      0x02
> -#define FLAG_GTSE               0x01
> -
>  static target_ulong h_register_process_table(PowerPCCPU *cpu,
>                                               sPAPRMachineState *spapr,
>                                               target_ulong opcode,
> @@ -943,12 +936,13 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
>      target_ulong table_size = args[3];
>      uint64_t cproc;
>  
> -    if (flags & ~FLAGS_MASK) { /* Check no reserved bits are set */
> +    if (flags & ~SPAPR_PROC_TABLE_MASK) { /* Check no reserved bits are set */
>          return H_PARAMETER;
>      }
> -    if (flags & FLAG_MODIFY) {
> -        if (flags & FLAG_REGISTER) {
> -            if (flags & FLAG_RADIX) { /* Register new RADIX process table */
> +    if (flags & SPAPR_PROC_TABLE_MODIFY) {
> +        if (flags & SPAPR_PROC_TABLE_REGISTER) {
> +            if (flags & SPAPR_PROC_TABLE_RADIX) {
> +                /* Register new RADIX process table */
>                  if (proc_tbl & 0xfff || proc_tbl >> 60) {
>                      return H_P2;
>                  } else if (page_size) {
> @@ -958,7 +952,8 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
>                  }
>                  cproc = PATBE1_GR | proc_tbl | table_size;
>              } else { /* Register new HPT process table */
> -                if (flags & FLAG_HASH_PROC_TBL) { /* Hash with Segment Tables */
> +                if (flags & SPAPR_PROC_TABLE_HPT_PT) {
> +                    /* Hash with Segment Tables */
>                      /* TODO - Not Supported */
>                      /* Technically caused by flag bits => H_PARAMETER */
>                      return H_PARAMETER;
> @@ -981,7 +976,8 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
>              cproc = spapr->patb_entry & PATBE1_GR;
>          }
>      } else { /* Maintain current registration */
> -        if (!(flags & FLAG_RADIX) != !(spapr->patb_entry & PATBE1_GR)) {
> +        if (!(flags & SPAPR_PROC_TABLE_RADIX) !=
> +            !(spapr->patb_entry & PATBE1_GR)) {
>              /* Technically caused by flag bits => H_PARAMETER */
>              return H_PARAMETER; /* Existing Process Table Mismatch */
>          }
> @@ -996,13 +992,14 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
>      /* Update the UPRT and GTSE bits in the LPCR for all cpus */
>      CPU_FOREACH(cs) {
>          set_spr(cs, SPR_LPCR, LPCR_UPRT | LPCR_GTSE,
> -                ((flags & (FLAG_RADIX | FLAG_HASH_PROC_TBL)) ? LPCR_UPRT : 0) |
> -                ((flags & FLAG_GTSE) ? LPCR_GTSE : 0));
> +                ((flags & (SPAPR_PROC_TABLE_RADIX | SPAPR_PROC_TABLE_HPT_PT)) ?
> +                LPCR_UPRT : 0) | ((flags & SPAPR_PROC_TABLE_GTSE) ?
> +                SPAPR_PROC_TABLE_GTSE : 0));
>      }
>  
>      if (kvm_enabled()) {
> -        return kvmppc_configure_v3_mmu(cpu, flags & FLAG_RADIX,
> -                                       flags & FLAG_GTSE, cproc);
> +        return kvmppc_configure_v3_mmu(cpu, flags & SPAPR_PROC_TABLE_RADIX,
> +                                       flags & SPAPR_PROC_TABLE_GTSE, cproc);
>      }
>      return H_SUCCESS;
>  }
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 5802f88..a692e63 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -681,4 +681,14 @@ int spapr_rng_populate_dt(void *fdt);
>  
>  void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
>  
> +/*
> + * Defines for flag value used in H_REGISTER_PROC_TBL hcall.
> + */
> +#define SPAPR_PROC_TABLE_MASK        0x01FULL
> +#define SPAPR_PROC_TABLE_MODIFY      0x10
> +#define SPAPR_PROC_TABLE_REGISTER    0x08
> +#define SPAPR_PROC_TABLE_RADIX       0x04
> +#define SPAPR_PROC_TABLE_HPT_PT      0x02
> +#define SPAPR_PROC_TABLE_GTSE        0x01
> +
>  #endif /* HW_SPAPR_H */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [Qemu-devel] [RFC PATCH 2/2] spapr: Fix migration of Radix guests

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 5737 bytes --]

On Mon, May 08, 2017 at 02:36:17PM +0530, Bharata B Rao wrote:
> Currently HTAB savevm handlers get registered by default and migration
> of radix guest will fail.
> 
> - Ensure that HTAB savevm handlers are not registered for radix case.
> - Ensure that we issue KVM_PPC_CONFIGURE_V3_MMU for radix case post
>   migration.
> 
> TODO: Right now I have delayed the HTAB savevm handler registration
> to CAS call where we know if the guest is radix or hash. Another approach
> is to let the HTAB handlers to be registered by default (as it is being
> done currently, but unregister them from CAS when we discover radix
> capability).

Option 2 there sounds messy.  I also suspect it could break if you try
to migrate an (eventually) radix guest before it's done CAS.

Strictly speaking only registering at CAS time will break old hash
guests that don't do CAS at all.  However such guests are really,
really ancient, and I suspect we don't work with them already.

You do, however, need to deregister (and allow the choice to be made
again) on guest reset.  On KVM we can only (for now) support either
hash or radix guests.  Under TCG, however, we could run a radix guest
then reboot to a hash guest or vice versa.


> 
> Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c         | 18 +++++++++++++++---
>  hw/ppc/spapr_hcall.c   |  5 +++++
>  include/hw/ppc/spapr.h |  3 +++
>  3 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e2dc77c..e14f55c 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1436,6 +1436,14 @@ static int spapr_post_load(void *opaque, int version_id)
>          err = spapr_rtc_import_offset(&spapr->rtc, spapr->rtc_offset);
>      }
>  
> +    if (spapr->patb_entry && (spapr->patb_flags & SPAPR_PROC_TABLE_RADIX) &&

patb_entry already tells you whether the guest is radix or not
(PATBE1_GR), you shouldn't need extra flags.

> +        kvmppc_has_cap_mmu_radix() && kvm_enabled()) {

You should also fail the migration if you have an incoming radix
guest, but the your new KVM host can't do radix.  Or the reverse, for
that matter.

> +        err = kvmppc_configure_v3_mmu(POWERPC_CPU(first_cpu),
> +                                      spapr->patb_flags &
> +                                      SPAPR_PROC_TABLE_RADIX,
> +                                      spapr->patb_flags & SPAPR_PROC_TABLE_GTSE,
> +                                      spapr->patb_entry);
> +    }
>      return err;
>  }
>  
> @@ -1520,6 +1528,7 @@ static const VMStateDescription vmstate_spapr_patb_entry = {
>      .needed = spapr_patb_entry_needed,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT64(patb_entry, sPAPRMachineState),
> +        VMSTATE_UINT64(patb_flags, sPAPRMachineState),
>          VMSTATE_END_OF_LIST()
>      },
>  };
> @@ -1869,6 +1878,12 @@ static SaveVMHandlers savevm_htab_handlers = {
>      .load_state = htab_load,
>  };
>  
> +void spapr_htab_savevm_register(sPAPRMachineState *spapr)
> +{
> +    register_savevm_live(NULL, "spapr/htab", -1, 1,
> +                         &savevm_htab_handlers, spapr);
> +}
> +
>  static void spapr_boot_set(void *opaque, const char *boot_device,
>                             Error **errp)
>  {
> @@ -2331,9 +2346,6 @@ static void ppc_spapr_init(MachineState *machine)
>       * interface, this is a legacy from the sPAPREnvironment structure
>       * which predated MachineState but had a similar function */
>      vmstate_register(NULL, 0, &vmstate_spapr, spapr);
> -    register_savevm_live(NULL, "spapr/htab", -1, 1,
> -                         &savevm_htab_handlers, spapr);
> -
>      /* used by RTAS */
>      QTAILQ_INIT(&spapr->ccs_list);
>      qemu_register_reset(spapr_ccs_reset_hook, spapr);
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 3600b0e..fa03ca0 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -988,6 +988,7 @@ static target_ulong h_register_process_table(PowerPCCPU *cpu,
>      spapr_check_setup_free_hpt(spapr, spapr->patb_entry, cproc);
>  
>      spapr->patb_entry = cproc; /* Save new process table */
> +    spapr->patb_flags = flags; /* Save the flags */
>  
>      /* Update the UPRT and GTSE bits in the LPCR for all cpus */
>      CPU_FOREACH(cs) {
> @@ -1169,6 +1170,10 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
>          }
>      }
>  
> +    /* Register savevm handlers for HTAB case */
> +    if (!guest_radix || !kvmppc_has_cap_mmu_radix()) {
> +        spapr_htab_savevm_register(spapr);
> +    }
>      return H_SUCCESS;
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index a692e63..0d0e9e4 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -75,6 +75,7 @@ struct sPAPRMachineState {
>      void *htab;
>      uint32_t htab_shift;
>      uint64_t patb_entry; /* Process tbl registed in H_REGISTER_PROCESS_TABLE */
> +    uint64_t patb_flags;
>      hwaddr rma_size;
>      int vrma_adjust;
>      ssize_t rtas_size;
> @@ -691,4 +692,6 @@ void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
>  #define SPAPR_PROC_TABLE_HPT_PT      0x02
>  #define SPAPR_PROC_TABLE_GTSE        0x01
>  
> +void spapr_htab_savevm_register(sPAPRMachineState *spapr);
> +
>  #endif /* HW_SPAPR_H */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [Qemu-devel] [RFC PATCH 2/2] spapr: Fix migration of Radix guests

[Bharata B Rao]

On Thu, May 11, 2017 at 11:02:20AM +1000, David Gibson wrote:
> On Mon, May 08, 2017 at 02:36:17PM +0530, Bharata B Rao wrote:
> > Currently HTAB savevm handlers get registered by default and migration
> > of radix guest will fail.
> > 
> > - Ensure that HTAB savevm handlers are not registered for radix case.
> > - Ensure that we issue KVM_PPC_CONFIGURE_V3_MMU for radix case post
> >   migration.
> > 
> > TODO: Right now I have delayed the HTAB savevm handler registration
> > to CAS call where we know if the guest is radix or hash. Another approach
> > is to let the HTAB handlers to be registered by default (as it is being
> > done currently, but unregister them from CAS when we discover radix
> > capability).
> 
> Option 2 there sounds messy.  I also suspect it could break if you try
> to migrate an (eventually) radix guest before it's done CAS.
> 
> Strictly speaking only registering at CAS time will break old hash
> guests that don't do CAS at all.  However such guests are really,
> really ancient, and I suspect we don't work with them already.
> 
> You do, however, need to deregister (and allow the choice to be made
> again) on guest reset.  On KVM we can only (for now) support either
> hash or radix guests.  Under TCG, however, we could run a radix guest
> then reboot to a hash guest or vice versa.

Took care of this in v1.

> 
> 
> > 
> > Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/spapr.c         | 18 +++++++++++++++---
> >  hw/ppc/spapr_hcall.c   |  5 +++++
> >  include/hw/ppc/spapr.h |  3 +++
> >  3 files changed, 23 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index e2dc77c..e14f55c 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1436,6 +1436,14 @@ static int spapr_post_load(void *opaque, int version_id)
> >          err = spapr_rtc_import_offset(&spapr->rtc, spapr->rtc_offset);
> >      }
> >  
> > +    if (spapr->patb_entry && (spapr->patb_flags & SPAPR_PROC_TABLE_RADIX) &&
> 
> patb_entry already tells you whether the guest is radix or not
> (PATBE1_GR), you shouldn't need extra flags.
> 
> > +        kvmppc_has_cap_mmu_radix() && kvm_enabled()) {
> 
> You should also fail the migration if you have an incoming radix
> guest, but the your new KVM host can't do radix.  Or the reverse, for
> that matter.

I have checks in v1 to fail migration of radix guest to a host that doesn't
support radix. But I don't see how we can detect and fail the migration
of hash guests into hosts that don't support hash from here (i,e., from
spapr_post_load). The hash guest's migration stream would have htab
savevm entries and the target will fail as it knows not about htab
savevm entries.

Regards,
Bharata.