arm/acpi: Permit MMIO access of Xen unused devices for Dom0

Firstly it permits full MMIO capabilities for Dom0. Then deny MMIO
access of Xen used devices, such as UART, GIC, SMMU. Currently, it only
denies the MMIO access of UART and GIC regions. For other Xen used
devices it could be added later when they are supported.

Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com>

xen/arch/arm/domain_build.c

@@ -1359,6 +1359,38 @@ static int prepare_dtb(struct domain *d, struct kernel_info *kinfo)
 #ifdef CONFIG_ACPI
 #define ACPI_DOM0_FDT_MIN_SIZE 4096
 
+static int acpi_iomem_deny_access(struct domain *d)
+{
+    acpi_status status;
+    struct acpi_table_spcr *spcr = NULL;
+    unsigned long gfn;
+    int rc;
+
+    /* Firstly permit full MMIO capabilities. */
+    rc = iomem_permit_access(d, 0UL, ~0UL);
+    if ( rc )
+        return rc;
+
+    /* TODO: Deny MMIO access for SMMU, GIC ITS */
+    status = acpi_get_table(ACPI_SIG_SPCR, 0,
+                            (struct acpi_table_header **)&spcr);
+
+    if ( ACPI_FAILURE(status) )
+    {
+        printk("Failed to get SPCR table\n");
+        return -EINVAL;
+    }
+
+    gfn = spcr->serial_port.address >> PAGE_SHIFT;
+    /* Deny MMIO access for UART */
+    rc = iomem_deny_access(d, gfn, gfn + 1);
+    if ( rc )
+        return rc;
+
+    /* Deny MMIO access for GIC regions */
+    return gic_iomem_deny_access(d);
+}
+
 static int acpi_permit_spi_access(struct domain *d)
 {
     int i, res;
@@ -1922,6 +1954,10 @@ static int prepare_acpi(struct domain *d, struct kernel_info *kinfo)
     if ( rc != 0 )
         return rc;
 
+    rc = acpi_iomem_deny_access(d);
+    if ( rc != 0 )
+        return rc;
+
     return 0;
 }
 #else