[RFC PATCH 0/3] mshv: Fix soft reboot by using scrub partition ioctl on init

[RFC PATCH 0/3] mshv: Fix soft reboot by using scrub partition ioctl on init

[Doru Blânzeanu]

This series is an RFC because, the kernel mshv driver changes that introduce
this ioctl, are not upstream yet.
Below is a link to the posted kernel patch.
https://lore.kernel.org/linux-hyperv/20261029062801.28598-2-wei.liu@kernel.org/

This patch series uses the SCRUB_PARTITION ioctl during reset to ensure a sane
state for the mshv driver.

The series consists of:
1. accel/mshv: mask mshv cpus as resetable
2. include/hw/hyperv: Add SCRUB_PARTITION ioctl
3. accel/mshv: use scrub_partition ioctl on init

The second commit that adds the SCRUB_PARTITION ioctl definition can be dropped
once the kernel patch is merged and the Qemu linux-headers are updated.

In short, the changes mark the vCPUs as resettable and run the SCRUB_PARTITION
ioctl on the `synchronize_post_reset` hook for the first vCPU.

Doru Blânzeanu (2):
  include/hw/hyperv: Add SCRUB_PARTITION ioctl
  accel/mshv: use scrub_partition ioctl on init

Magnus Kulke (1):
  accel/mshv: mark mshv cpus as resetable

 accel/mshv/mshv-all.c          | 27 +++++++++++++++++++++++++--
 include/hw/hyperv/hvgdk_mini.h |  2 ++
 2 files changed, 27 insertions(+), 2 deletions(-)

-- 
2.54.0

[RFC PATCH 1/3] accel/mshv: mark mshv cpus as resetable

[Doru Blânzeanu]

From: Magnus Kulke <magnuskulke@linux.microsoft.com>

Guest using the MSHV accelerator aren't resetable otherwise.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Signed-off-by: Doru Blânzeanu <dblanzeanu@linux.microsoft.com>
---
 accel/mshv/mshv-all.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index d820a67b95..a7b7017fb1 100644
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -952,7 +952,7 @@ static void mshv_cpu_synchronize(CPUState *cpu)
 
 static bool mshv_cpus_are_resettable(void)
 {
-    return false;
+    return true;
 }
 
 static void mshv_accel_class_init(ObjectClass *oc, const void *data)
-- 
2.54.0

[RFC PATCH 2/3] include/hw/hyperv: Add SCRUB_PARTITION ioctl

[Doru Blânzeanu]

Signed-off-by: Doru Blânzeanu <dblanzeanu@linux.microsoft.com>
---
 include/hw/hyperv/hvgdk_mini.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/hw/hyperv/hvgdk_mini.h b/include/hw/hyperv/hvgdk_mini.h
index 0983e3a58d..5178ed07a1 100644
--- a/include/hw/hyperv/hvgdk_mini.h
+++ b/include/hw/hyperv/hvgdk_mini.h
@@ -545,6 +545,8 @@ struct hv_input_assert_virtual_interrupt {
 #define MSHV_IOEVENTFD              _IOW(MSHV_IOCTL, 0x04, struct mshv_user_ioeventfd)
 #define MSHV_SET_MSI_ROUTING        _IOW(MSHV_IOCTL, 0x05, struct mshv_user_irq_table)
 
+#define MSHV_SCRUB_PARTITION        _IO(MSHV_IOCTL, 0x0B)
+
 /*
  ********************************
  * VP APIs for child partitions *
-- 
2.54.0

[RFC PATCH 3/3] accel/mshv: use scrub_partition ioctl on init

[Doru Blânzeanu]

This is relevant on soft resets, when the MSHV partition will have a
preinitialized state for guest enlightenments and LAPIC state.
Without invoking the ioctl, a rebooted guest will fail during boot
when attempting to init Hyper-V enlightenments or the APIC.

Signed-off-by: Doru Blânzeanu <dblanzeanu@linux.microsoft.com>
---
 accel/mshv/mshv-all.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index a7b7017fb1..5e51d0f1fa 100644
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -84,6 +84,17 @@ static int mshv_load_cleanup(void *opaque)
     return 0;
 }
 
+static int scrub_partition(int vm_fd)
+{
+    int ret = ioctl(vm_fd, MSHV_SCRUB_PARTITION);
+
+    if (ret < 0) {
+        error_report("Failed to scrub partition");
+        return -errno;
+    }
+
+    return 0;
+}
 
 static int get_host_partition_property(int mshv_fd, uint32_t property_code,
                                        uint64_t *value)
@@ -906,7 +917,19 @@ static void mshv_cpu_synchronize_post_init(CPUState *cpu)
 
 static void mshv_cpu_synchronize_post_reset(CPUState *cpu)
 {
-    int ret = mshv_arch_store_vcpu_state(cpu);
+    int ret;
+    bool is_bsp = (cpu == first_cpu);
+
+    if (is_bsp) {
+        ret = scrub_partition(mshv_state->vm);
+        if (ret < 0) {
+            error_report("Failed to scrub partition during reset: %s",
+                         strerror(-ret));
+            vm_stop(RUN_STATE_INTERNAL_ERROR);
+        }
+    }
+
+    ret = mshv_arch_store_vcpu_state(cpu);
     if (ret) {
         error_report("Failed to put registers after reset: %s",
                      strerror(-ret));
-- 
2.54.0