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Re: [Xen-devel] [PATCH v6 05/12] x86/domctl: Handle ACPI access from domctl



On 01/03/2017 02:04 PM, Boris Ostrovsky wrote:
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v6:
* Adjustments to to patch 4 changes.
* Added a spinlock for VCPU map access
* Return an error on guest trying to write VCPU map

snip
-static int acpi_cpumap_access_common(struct domain *d, bool is_write,
-                                     unsigned int port,
+static int acpi_cpumap_access_common(struct domain *d, bool is_guest_access,
+                                     bool is_write, unsigned int port,
                                       unsigned int bytes, uint32_t *val)
  {
      unsigned int first_byte = port - XEN_ACPI_CPU_MAP;
+    int rc = X86EMUL_OKAY;

      BUILD_BUG_ON(XEN_ACPI_CPU_MAP + XEN_ACPI_CPU_MAP_LEN
                   > ACPI_GPE0_BLK_ADDRESS_V1);

+    spin_lock(&d->arch.hvm_domain.acpi_lock);
+
      if ( !is_write )
      {
          uint32_t mask = (bytes < 4) ? ~0U << (bytes * 8) : 0;
@@ -32,23 +37,61 @@ static int acpi_cpumap_access_common(struct domain *d, bool 
is_write,
              memcpy(val, (uint8_t *)d->avail_vcpus + first_byte,
                     min(bytes, ((d->max_vcpus + 7) / 8) - first_byte));
      }
+    else if ( !is_guest_access )
+        memcpy((uint8_t *)d->avail_vcpus + first_byte, val,
+               min(bytes, ((d->max_vcpus + 7) / 8) - first_byte));
      else
          /* Guests do not write CPU map */
-        return X86EMUL_UNHANDLEABLE;
+        rc = X86EMUL_UNHANDLEABLE;

-    return X86EMUL_OKAY;
+    spin_unlock(&d->arch.hvm_domain.acpi_lock);
+
+    return rc;
  }

  int hvm_acpi_domctl_access(struct domain *d,
                             const struct xen_domctl_acpi_access *access)
  {
-    return -ENOSYS;
+    unsigned int bytes, i;
+    uint32_t val = 0;
+    uint8_t *ptr = (uint8_t *)&val;
+    int rc;
+    bool is_write = (access->rw == XEN_DOMCTL_ACPI_WRITE) ? true : false;
+
+    if ( has_acpi_dm_ff(d) )
+        return -EOPNOTSUPP;
+
+    if ( access->space_id != XEN_ACPI_SYSTEM_IO )
+        return -EINVAL;
+
+    if ( !((access->address >= XEN_ACPI_CPU_MAP) &&
+           (access->address < XEN_ACPI_CPU_MAP + XEN_ACPI_CPU_MAP_LEN)) )
+        return -ENODEV;
+
+    for ( i = 0; i < access->width; i += sizeof(val) )
+    {
+        bytes = (access->width - i > sizeof(val)) ?
+            sizeof(val) : access->width - i;
+
+        if ( is_write && copy_from_guest_offset(ptr, access->val, i, bytes) )
+            return -EFAULT;
+
+        rc = acpi_cpumap_access_common(d, false, is_write,
+                                       access->address, bytes, &val);

While I'm looking at this code...
This doesn't work if access->width > sizeof(val) (4 bytes). The same value (access->address) is always passed into acpi_cpumap_access_common for 'port' and this is used as an offset into the avail_cpus array. So the offset is unchanged and only the first 4 bytes of avail_cpus ever gets changed.

--
Ross Lagerwall

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