[Xen-devel] [PATCH 2/3] EFI: allow to suppress the use of runtime services

["Jan Beulich" <JBeulich@xxxxxxxx>]

On certain systems some of the memory map entries designated for use by
runtime services cannot be mapped (frequently due to firmware bugs). On
others, some of the memory map entries aren't even marked for runtime
services use, yet are being used by them. For both cases give people a
way to suppress use of runtime services altogether.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -565,6 +565,13 @@ Either force retrieval of monitor EDID i
 disable it (edid=no). This option should not normally be required
 except for debugging purposes.
 
+### efi-rs
+> `= <boolean>`
+
+> Default: `true`
+
+Force or disable use of EFI runtime services.
+
 ### extra\_guest\_irqs
 > `= [<domU number>][,<dom0 number>]`
 
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1072,6 +1072,10 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
 }
 
 #ifndef CONFIG_ARM /* TODO - runtime service support */
+
+static bool_t __initdata efi_rs_enable = 1;
+boolean_param("efi-rs", efi_rs_enable);
+
 #ifndef USE_SET_VIRTUAL_ADDRESS_MAP
 static __init void copy_mapping(unsigned long mfn, unsigned long end,
                                 bool_t (*is_valid)(unsigned long smfn,
@@ -1145,7 +1149,7 @@ void __init efi_init_memory(void)
                desc->PhysicalStart, desc->PhysicalStart + len - 1,
                desc->Type, desc->Attribute);
 
-        if ( !(desc->Attribute & EFI_MEMORY_RUNTIME) )
+        if ( !efi_rs_enable || !(desc->Attribute & EFI_MEMORY_RUNTIME) )
             continue;
 
         desc->VirtualStart = INVALID_VIRTUAL_ADDRESS;
@@ -1209,6 +1213,12 @@ void __init efi_init_memory(void)
         }
     }
 
+    if ( !efi_rs_enable )
+    {
+        efi_fw_vendor = NULL;
+        return;
+    }
+
 #ifdef USE_SET_VIRTUAL_ADDRESS_MAP
     efi_rs->SetVirtualAddressMap(efi_memmap_size, efi_mdesc_size,
                                  mdesc_ver, efi_memmap);
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -56,6 +56,9 @@ unsigned long efi_rs_enter(void)
     static const u32 mxcsr = MXCSR_DEFAULT;
     unsigned long cr3 = read_cr3();
 
+    if ( !efi_l4_pgtable )
+        return 0;
+
     save_fpu_enable();
     asm volatile ( "fldcw %0" :: "m" (fcw) );
     asm volatile ( "ldmxcsr %0" :: "m" (mxcsr) );
@@ -83,6 +86,8 @@ unsigned long efi_rs_enter(void)
 
 void efi_rs_leave(unsigned long cr3)
 {
+    if ( !cr3 )
+        return;
     write_cr3(cr3);
     if ( is_pv_vcpu(current) && !is_idle_vcpu(current) )
     {
@@ -100,7 +105,7 @@ void efi_rs_leave(unsigned long cr3)
 
 paddr_t efi_rs_page_table(void)
 {
-    return virt_to_maddr(efi_l4_pgtable);
+    return efi_l4_pgtable ? virt_to_maddr(efi_l4_pgtable) : 0;
 }
 
 unsigned long efi_get_time(void)
@@ -109,6 +114,8 @@ unsigned long efi_get_time(void)
     EFI_STATUS status;
     unsigned long cr3 = efi_rs_enter(), flags;
 
+    if ( !cr3 )
+        return 0;
     spin_lock_irqsave(&rtc_lock, flags);
     status = efi_rs->GetTime(&time, NULL);
     spin_unlock_irqrestore(&rtc_lock, flags);
@@ -126,6 +133,8 @@ void efi_halt_system(void)
     EFI_STATUS status;
     unsigned long cr3 = efi_rs_enter();
 
+    if ( !cr3 )
+        return;
     status = efi_rs->ResetSystem(EfiResetShutdown, EFI_SUCCESS, 0, NULL);
     efi_rs_leave(cr3);
 
@@ -137,6 +146,8 @@ void efi_reset_system(bool_t warm)
     EFI_STATUS status;
     unsigned long cr3 = efi_rs_enter();
 
+    if ( !cr3 )
+        return;
     status = efi_rs->ResetSystem(warm ? EfiResetWarm : EfiResetCold,
                                  EFI_SUCCESS, 0, NULL);
     efi_rs_leave(cr3);
@@ -161,6 +172,8 @@ int efi_get_info(uint32_t idx, union xen
     {
         unsigned long cr3 = efi_rs_enter();
 
+        if ( !cr3 )
+            return -EOPNOTSUPP;
         info->version = efi_rs->Hdr.Revision;
         efi_rs_leave(cr3);
         break;
@@ -170,6 +183,8 @@ int efi_get_info(uint32_t idx, union xen
         info->cfg.nent = efi_num_ct;
         break;
     case XEN_FW_EFI_VENDOR:
+        if ( !efi_fw_vendor )
+            return -EOPNOTSUPP;
         info->vendor.revision = efi_fw_revision;
         n = info->vendor.bufsz / sizeof(*efi_fw_vendor);
         if ( !guest_handle_okay(guest_handle_cast(info->vendor.name,
@@ -292,6 +307,8 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
+        if ( !cr3 )
+            return -EOPNOTSUPP;
         spin_lock_irqsave(&rtc_lock, flags);
         status = efi_rs->GetTime(cast_time(&op->u.get_time.time), &caps);
         spin_unlock_irqrestore(&rtc_lock, flags);
@@ -312,6 +329,8 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
+        if ( !cr3 )
+            return -EOPNOTSUPP;
         spin_lock_irqsave(&rtc_lock, flags);
         status = efi_rs->SetTime(cast_time(&op->u.set_time));
         spin_unlock_irqrestore(&rtc_lock, flags);
@@ -326,6 +345,8 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
+        if ( !cr3 )
+            return -EOPNOTSUPP;
         spin_lock_irqsave(&rtc_lock, flags);
         status = efi_rs->GetWakeupTime(&enabled, &pending,
                                        cast_time(&op->u.get_wakeup_time));
@@ -348,6 +369,8 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
+        if ( !cr3 )
+            return -EOPNOTSUPP;
         spin_lock_irqsave(&rtc_lock, flags);
         status = efi_rs->SetWakeupTime(!!(op->misc &
                                           XEN_EFI_SET_WAKEUP_TIME_ENABLE),
@@ -366,7 +389,10 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
-        status = efi_rs->GetNextHighMonotonicCount(&op->misc);
+        if ( cr3 )
+            status = efi_rs->GetNextHighMonotonicCount(&op->misc);
+        else
+            rc = -EOPNOTSUPP;
         efi_rs_leave(cr3);
         break;
 
@@ -402,15 +428,20 @@ int efi_runtime_call(struct xenpf_efi_ru
             data = NULL;
 
         cr3 = efi_rs_enter();
-        status = efi_rs->GetVariable(
-            name, cast_guid(&op->u.get_variable.vendor_guid),
-            &op->misc, &size, data);
-        efi_rs_leave(cr3);
+        if ( cr3 )
+        {
+            status = efi_rs->GetVariable(
+                name, cast_guid(&op->u.get_variable.vendor_guid),
+                &op->misc, &size, data);
+            efi_rs_leave(cr3);
 
-        if ( !EFI_ERROR(status) &&
-             copy_to_guest(op->u.get_variable.data, data, size) )
-            rc = -EFAULT;
-        op->u.get_variable.size = size;
+            if ( !EFI_ERROR(status) &&
+                 copy_to_guest(op->u.get_variable.data, data, size) )
+                rc = -EFAULT;
+            op->u.get_variable.size = size;
+        }
+        else
+            rc = -EOPNOTSUPP;
 
         xfree(data);
         xfree(name);
@@ -440,9 +471,12 @@ int efi_runtime_call(struct xenpf_efi_ru
         else
         {
             cr3 = efi_rs_enter();
-            status = efi_rs->SetVariable(
-                name, cast_guid(&op->u.set_variable.vendor_guid),
-                op->misc, op->u.set_variable.size, data);
+            if ( cr3 )
+                status = efi_rs->SetVariable(
+                    name, cast_guid(&op->u.set_variable.vendor_guid),
+                    op->misc, op->u.set_variable.size, data);
+            else
+                rc = -EOPNOTSUPP;
             efi_rs_leave(cr3);
         }
 
@@ -474,15 +508,21 @@ int efi_runtime_call(struct xenpf_efi_ru
         }
 
         cr3 = efi_rs_enter();
-        status = efi_rs->GetNextVariableName(
-            &size, name.str,
-            cast_guid(&op->u.get_next_variable_name.vendor_guid));
-        efi_rs_leave(cr3);
+        if ( cr3 )
+        {
+            status = efi_rs->GetNextVariableName(
+                &size, name.str,
+                cast_guid(&op->u.get_next_variable_name.vendor_guid));
+            efi_rs_leave(cr3);
 
-        if ( !EFI_ERROR(status) &&
-             copy_to_guest(op->u.get_next_variable_name.name, name.raw, size) )
-            rc = -EFAULT;
-        op->u.get_next_variable_name.size = size;
+            if ( !EFI_ERROR(status) &&
+                 copy_to_guest(op->u.get_next_variable_name.name,
+                               name.raw, size) )
+                rc = -EFAULT;
+            op->u.get_next_variable_name.size = size;
+        }
+        else
+            rc = -EOPNOTSUPP;
 
         xfree(name.raw);
     }
@@ -519,7 +559,7 @@ int efi_runtime_call(struct xenpf_efi_ru
         }
 
         cr3 = efi_rs_enter();
-        if ( (efi_rs->Hdr.Revision >> 16) < 2 )
+        if ( !cr3 || (efi_rs->Hdr.Revision >> 16) < 2 )
         {
             efi_rs_leave(cr3);
             return -EOPNOTSUPP;
@@ -538,7 +578,7 @@ int efi_runtime_call(struct xenpf_efi_ru
             return -EINVAL;
 
         cr3 = efi_rs_enter();
-        if ( (efi_rs->Hdr.Revision >> 16) < 2 )
+        if ( !cr3 || (efi_rs->Hdr.Revision >> 16) < 2 )
         {
             efi_rs_leave(cr3);
             return -EOPNOTSUPP;

Attachment: EFI-suppress-RS.patch
Description: Text document

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