[Xen-devel] [PATCH v4 3/3] xen/efi: use directmap to access runtime services table

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

Do not require switching page tables to access (static) information in
the runtime services table itself, use directmap for this. This allows
exiting early from XEN_EFI_query_capsule_capabilities,
XEN_EFI_update_capsule and XEN_EFI_query_variable_info (in case of not
supported call) without all the impact of page table switch.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
New patch in v4. Can be applied independently of the other two.
Specifically can be defered beyond 4.13.
I'm also fine with dropping it, if adding directmap users is undesired.

Cc: Juergen Gross <jgross@suse.com>
---
 xen/common/efi/boot.c    |  1 +
 xen/common/efi/runtime.c | 19 ++++---------------
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 9debc5b..89b1c8a 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1122,6 +1122,7 @@ static void __init efi_exit_boot(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *Syste
 
     /* Adjust pointers into EFI. */
     efi_ct = (void *)efi_ct + DIRECTMAP_VIRT_START;
+    efi_rs = (void *)efi_rs + DIRECTMAP_VIRT_START;
     efi_memmap = (void *)efi_memmap + DIRECTMAP_VIRT_START;
     efi_fw_vendor = (void *)efi_fw_vendor + DIRECTMAP_VIRT_START;
 }
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index ab53ebc..22fd6c9 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -211,12 +211,7 @@ int efi_get_info(uint32_t idx, union xenpf_efi_info *info)
         break;
     case XEN_FW_EFI_RT_VERSION:
     {
-        struct efi_rs_state state = efi_rs_enter();
-
-        if ( !state.cr3 )
-            return -EOPNOTSUPP;
         info->version = efi_rs->Hdr.Revision;
-        efi_rs_leave(&state);
         break;
     }
     case XEN_FW_EFI_CONFIG_TABLE:
@@ -618,12 +613,11 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
             break;
         }
 
+        if ( (efi_rs->Hdr.Revision >> 16) < 2 )
+            return -EOPNOTSUPP;
         state = efi_rs_enter();
-        if ( !state.cr3 || (efi_rs->Hdr.Revision >> 16) < 2 )
-        {
-            efi_rs_leave(&state);
+        if ( !state.cr3 )
             return -EOPNOTSUPP;
-        }
         status = efi_rs->QueryVariableInfo(
             op->u.query_variable_info.attr,
             &op->u.query_variable_info.max_store_size,
@@ -637,13 +631,8 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
         if ( op->misc )
             return -EINVAL;
 
-        state = efi_rs_enter();
-        if ( !state.cr3 || (efi_rs->Hdr.Revision >> 16) < 2 )
-        {
-            efi_rs_leave(&state);
+        if ( (efi_rs->Hdr.Revision >> 16) < 2 )
             return -EOPNOTSUPP;
-        }
-        efi_rs_leave(&state);
         /* XXX fall through for now */
     default:
         return -ENOSYS;
-- 
git-series 0.9.1

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