[Qemu-devel] [PATCH 0/3] Arm migration fixes for 3.0

[Qemu-devel] [PATCH 0/3] Arm migration fixes for 3.0

[Peter Maydell]

This patchset primarily fixes problems with Arm migration
induced by a bug in the core vmstate handling of subsections:
currently the migration code incorrectly treats a subsection with
no .needed function pointer as if it was the subsection list
terminator -- it is ignored and so is everything after it.

I did an audit of all uses of subsections in QEMU, and found
that we had four which didn't define a .needed function (assuming
that this meant "always needed", same as the semantics for
not providing a .needed function for a toplevel vmsd).
This patchset fixes them all up by providing a dummy needed
function.

It also fixes an error in vmstate_gicv3_cpu which was accidentally
initializing .subsections twice and so ignoring one of the subsections.

Strictly speaking only the first patch is a true regression from 2.12.

Disclaimer: compile tested only as I have to rush out the door in a
moment, but I wanted to get these on-list for review given that
rc4 isn't too far away... I'll test them properly on Monday.

thanks
-- PMM

Peter Maydell (3):
  hw/intc/arm_gicv3_common: Give no-migration-shift-bug subsection a
    needed function
  hw/intc/arm_gicv3_common: Combine duplicate .subsections in
    vmstate_gicv3_cpu
  target/arm: Add dummy needed functions to M profile vmstate
    subsections

 hw/intc/arm_gicv3_common.c | 9 ++++++---
 target/arm/machine.c       | 3 +++
 2 files changed, 9 insertions(+), 3 deletions(-)

-- 
2.17.1

[Qemu-devel] [PATCH 1/3] hw/intc/arm_gicv3_common: Give no-migration-shift-bug subsection a needed function

[Peter Maydell]

Currently the migration code incorrectly treats a subsection with
no .needed function pointer as if it was the subsection list
terminator -- it is ignored and so is everything after it.
Work around this by giving vmstate_gicv3_gicd_no_migration_shift_bug
a 'needed' function that always returns true.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
This should go into 3.0 to avoid awkward migration compat problems:
the no-migration-shift-bug subsection is new in 3.0.
---
 hw/intc/arm_gicv3_common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
index ff326b374ad..e58bc8b8105 100644
--- a/hw/intc/arm_gicv3_common.c
+++ b/hw/intc/arm_gicv3_common.c
@@ -203,10 +203,16 @@ static int gicv3_gicd_no_migration_shift_bug_post_load(void *opaque,
     return 0;
 }
 
+static bool needed_always(void *opaque)
+{
+    return true;
+}
+
 const VMStateDescription vmstate_gicv3_gicd_no_migration_shift_bug = {
     .name = "arm_gicv3/gicd_no_migration_shift_bug",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = needed_always,
     .pre_load = gicv3_gicd_no_migration_shift_bug_pre_load,
     .post_load = gicv3_gicd_no_migration_shift_bug_post_load,
     .fields = (VMStateField[]) {
-- 
2.17.1

[Qemu-devel] [PATCH 2/3] hw/intc/arm_gicv3_common: Combine duplicate .subsections in vmstate_gicv3_cpu

[Peter Maydell]

Commit 6692aac411199064 accidentally introduced a second initialization
of the .subsections field of vmstate_gicv3_cpu, instead of adding
the new subsection to the existing list. The effect of this was
probably that migration of GICv3 with virtualization enabled was
broken (or alternatively that migration of ICC_SRE_EL1 was broken,
depending on which of the two initializers the compiler used).
Combine the two into a single list.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Not strictly a 2.12 regression.
---
 hw/intc/arm_gicv3_common.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
index e58bc8b8105..e1a8999cf5b 100644
--- a/hw/intc/arm_gicv3_common.c
+++ b/hw/intc/arm_gicv3_common.c
@@ -134,9 +134,6 @@ static const VMStateDescription vmstate_gicv3_cpu = {
     },
     .subsections = (const VMStateDescription * []) {
         &vmstate_gicv3_cpu_virt,
-        NULL
-    },
-    .subsections = (const VMStateDescription * []) {
         &vmstate_gicv3_cpu_sre_el1,
         NULL
     }
-- 
2.17.1

[Qemu-devel] [PATCH 3/3] target/arm: Add dummy needed functions to M profile vmstate subsections

[Peter Maydell]

Currently the migration code incorrectly treats a subsection with
no .needed function pointer as if it was the subsection list
terminator -- it is ignored and so is everything after it.
Work around this by giving various M profile vmstate structs
a 'needed' function that always returns true.
We reuse m_needed() for this, since it's always true here.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Not strictly a regression as it only affects M profile CPUs
with the security extensions, and migration of those was
broken anyway in 2.12 due to a different bug.
---
 target/arm/machine.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/target/arm/machine.c b/target/arm/machine.c
index 2e28d086bdf..ff4ec22bf75 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -184,6 +184,7 @@ static const VMStateDescription vmstate_m_faultmask_primask = {
     .name = "cpu/m/faultmask-primask",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.faultmask[M_REG_NS], ARMCPU),
         VMSTATE_UINT32(env.v7m.primask[M_REG_NS], ARMCPU),
@@ -230,6 +231,7 @@ static const VMStateDescription vmstate_m_scr = {
     .name = "cpu/m/scr",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.scr[M_REG_NS], ARMCPU),
         VMSTATE_END_OF_LIST()
@@ -240,6 +242,7 @@ static const VMStateDescription vmstate_m_other_sp = {
     .name = "cpu/m/other-sp",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.other_sp, ARMCPU),
         VMSTATE_END_OF_LIST()
-- 
2.17.1

Re: [Qemu-devel] [PATCH 2/3] hw/intc/arm_gicv3_common: Combine duplicate .subsections in vmstate_gicv3_cpu

[Dr. David Alan Gilbert]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> Commit 6692aac411199064 accidentally introduced a second initialization
> of the .subsections field of vmstate_gicv3_cpu, instead of adding
> the new subsection to the existing list. The effect of this was
> probably that migration of GICv3 with virtualization enabled was
> broken (or alternatively that migration of ICC_SRE_EL1 was broken,
> depending on which of the two initializers the compiler used).
> Combine the two into a single list.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
> Not strictly a 2.12 regression.
> ---
>  hw/intc/arm_gicv3_common.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
> index e58bc8b8105..e1a8999cf5b 100644
> --- a/hw/intc/arm_gicv3_common.c
> +++ b/hw/intc/arm_gicv3_common.c
> @@ -134,9 +134,6 @@ static const VMStateDescription vmstate_gicv3_cpu = {
>      },
>      .subsections = (const VMStateDescription * []) {
>          &vmstate_gicv3_cpu_virt,
> -        NULL
> -    },
> -    .subsections = (const VMStateDescription * []) {
>          &vmstate_gicv3_cpu_sre_el1,
>          NULL
>      }
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 1/3] hw/intc/arm_gicv3_common: Give no-migration-shift-bug subsection a needed function

[Dr. David Alan Gilbert]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> Currently the migration code incorrectly treats a subsection with
> no .needed function pointer as if it was the subsection list
> terminator -- it is ignored and so is everything after it.
> Work around this by giving vmstate_gicv3_gicd_no_migration_shift_bug
> a 'needed' function that always returns true.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
> This should go into 3.0 to avoid awkward migration compat problems:
> the no-migration-shift-bug subsection is new in 3.0.
> ---
>  hw/intc/arm_gicv3_common.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
> index ff326b374ad..e58bc8b8105 100644
> --- a/hw/intc/arm_gicv3_common.c
> +++ b/hw/intc/arm_gicv3_common.c
> @@ -203,10 +203,16 @@ static int gicv3_gicd_no_migration_shift_bug_post_load(void *opaque,
>      return 0;
>  }
>  
> +static bool needed_always(void *opaque)
> +{
> +    return true;
> +}
> +
>  const VMStateDescription vmstate_gicv3_gicd_no_migration_shift_bug = {
>      .name = "arm_gicv3/gicd_no_migration_shift_bug",
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .needed = needed_always,
>      .pre_load = gicv3_gicd_no_migration_shift_bug_pre_load,
>      .post_load = gicv3_gicd_no_migration_shift_bug_post_load,
>      .fields = (VMStateField[]) {
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 3/3] target/arm: Add dummy needed functions to M profile vmstate subsections

[Dr. David Alan Gilbert]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> Currently the migration code incorrectly treats a subsection with
> no .needed function pointer as if it was the subsection list
> terminator -- it is ignored and so is everything after it.
> Work around this by giving various M profile vmstate structs
> a 'needed' function that always returns true.
> We reuse m_needed() for this, since it's always true here.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
> Not strictly a regression as it only affects M profile CPUs
> with the security extensions, and migration of those was
> broken anyway in 2.12 due to a different bug.
> ---
>  target/arm/machine.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/target/arm/machine.c b/target/arm/machine.c
> index 2e28d086bdf..ff4ec22bf75 100644
> --- a/target/arm/machine.c
> +++ b/target/arm/machine.c
> @@ -184,6 +184,7 @@ static const VMStateDescription vmstate_m_faultmask_primask = {
>      .name = "cpu/m/faultmask-primask",
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .needed = m_needed,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT32(env.v7m.faultmask[M_REG_NS], ARMCPU),
>          VMSTATE_UINT32(env.v7m.primask[M_REG_NS], ARMCPU),
> @@ -230,6 +231,7 @@ static const VMStateDescription vmstate_m_scr = {
>      .name = "cpu/m/scr",
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .needed = m_needed,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT32(env.v7m.scr[M_REG_NS], ARMCPU),
>          VMSTATE_END_OF_LIST()
> @@ -240,6 +242,7 @@ static const VMStateDescription vmstate_m_other_sp = {
>      .name = "cpu/m/other-sp",
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .needed = m_needed,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT32(env.v7m.other_sp, ARMCPU),
>          VMSTATE_END_OF_LIST()
> -- 
> 2.17.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [Qemu-arm] [PATCH 1/3] hw/intc/arm_gicv3_common: Give no-migration-shift-bug subsection a needed function

[Peter Maydell]

Forgot to cc Shannon on this one. Given that the missing .needed
function meant we weren't ever transmitting the subsection with
the no-shift-bug flag, this ought to mean that for current
master migration of KVM goes wrong (since the destination thinks
the source has the bug when it does not). I'm just going to try
to set up to test this...

thanks
-- PMM

On 3 August 2018 at 17:36, Peter Maydell <peter.maydell@linaro.org> wrote:
> Currently the migration code incorrectly treats a subsection with
> no .needed function pointer as if it was the subsection list
> terminator -- it is ignored and so is everything after it.
> Work around this by giving vmstate_gicv3_gicd_no_migration_shift_bug
> a 'needed' function that always returns true.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> This should go into 3.0 to avoid awkward migration compat problems:
> the no-migration-shift-bug subsection is new in 3.0.
> ---
>  hw/intc/arm_gicv3_common.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
> index ff326b374ad..e58bc8b8105 100644
> --- a/hw/intc/arm_gicv3_common.c
> +++ b/hw/intc/arm_gicv3_common.c
> @@ -203,10 +203,16 @@ static int gicv3_gicd_no_migration_shift_bug_post_load(void *opaque,
>      return 0;
>  }
>
> +static bool needed_always(void *opaque)
> +{
> +    return true;
> +}
> +
>  const VMStateDescription vmstate_gicv3_gicd_no_migration_shift_bug = {
>      .name = "arm_gicv3/gicd_no_migration_shift_bug",
>      .version_id = 1,
>      .minimum_version_id = 1,
> +    .needed = needed_always,
>      .pre_load = gicv3_gicd_no_migration_shift_bug_pre_load,
>      .post_load = gicv3_gicd_no_migration_shift_bug_post_load,
>      .fields = (VMStateField[]) {
> --
> 2.17.1