Section

  7.7 Adding the Exit Boot Services feature

in

  Driver Writer's Guide for UEFI 2.3.1 (v1.01)

writes,

> Examples from the EDK II that use this feature are the PCI device
> drivers for USB Host Controllers. Some USB Host Controllers are PCI Bus
> Masters that continuously access a memory buffer to poll for operation
> requests. Access to this memory buffer by a USB Host Controller may be
> required to boot an operation system, but this activity must be
> terminated when the OS calls ExitBootServices() . The typical action in
> the Exit Boot Services Event for these types of drivers is to disable
> the PCI bus master and place the USB Host Controller into a halted
> state.

EhcExitBootService() already resets the host controller, which causes the
host controller to forget about all common buffers configured previously.

However, if the system has a component that translates device addresses to
system memory addresses (such as an IOMMU), then the translations put in
place when the common buffers were originally mapped should also be
undone, before handing control to the OS.

EhciDxe maps two kinds of common buffers:

(1) The Frame List is initially mapped in

      EhcDriverBindingStart()
        EhcInitHC()
          EhcInitSched()

    and it is unmapped and mapped again, for an unspecified number of
    times, in

      EhcReset()
        EhcFreeSched()
        EhcInitHC()
          EhcInitSched()

(2) Memory blocks in the USB Host Controller memory pool are first added
    in

      UhciDriverBindingStart()
        EhcInitHC()
          EhcInitSched()
            UsbHcInitMemPool()
              UsbHcAllocMemBlock()

    then for an unspecified number of times in

      UsbHcAllocateMem()
        UsbHcAllocMemBlock()

    whenever the pool has to be extended. Memory blocks are also unmapped
    and mapped again in

      EhcReset()
        EhcFreeSched()
          UsbHcFreeMemPool()
            UsbHcFreeMemBlock()
        EhcInitHC()
          EhcInitSched()
            UsbHcInitMemPool()
              UsbHcAllocMemBlock()

Both kinds of common buffers are unmapped in the following call tree:

  EhcDriverBindingStop()
    EhcFreeSched() <-
      UsbHcFreeMemPool()
        UsbHcFreeMemBlock()

The common buffers should be unmapped at ExitBootServices() the same way.
In that context however, we must not free memory (because that could alter
the UEFI memory map, which is forbidden for ExitBootServices()
notification functions). So call PciIo->Unmap() without calling
PciIo->FreeBuffer().

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdeModulePkg/Bus/Pci/EhciDxe/Ehci.c | 25 +++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Pci/EhciDxe/Ehci.c b/MdeModulePkg/Bus/Pci/EhciDxe/Ehci.c
index 5173a9d599c5..441366244c9a 100644
--- a/MdeModulePkg/Bus/Pci/EhciDxe/Ehci.c
+++ b/MdeModulePkg/Bus/Pci/EhciDxe/Ehci.c
@@ -1644,7 +1644,9 @@ EhcExitBootService (
   )
 
 {
-  USB2_HC_DEV   *Ehc;
+  USB2_HC_DEV     *Ehc;
+  USBHC_MEM_POOL  *MemPool;
+  USBHC_MEM_BLOCK *MemBlock;
 
   Ehc = (USB2_HC_DEV *) Context;
 
@@ -1652,6 +1654,27 @@ EhcExitBootService (
   // Reset the Host Controller
   //
   EhcResetHC (Ehc, EHC_RESET_TIMEOUT);
+
+  //
+  // Unmap the frame list.
+  //
+  if (Ehc->PeriodFrame != NULL) {
+    Ehc->PciIo->Unmap (Ehc->PciIo, Ehc->PeriodFrameMap);
+  }
+
+  //
+  // Unmap the memory pool.
+  //
+  MemPool = Ehc->MemPool;
+  if (MemPool != NULL) {
+    for (MemBlock = MemPool->Head;
+         MemBlock != NULL;
+         MemBlock = MemBlock->Next) {
+      if (MemBlock->BufHost != NULL) {
+        MemPool->PciIo->Unmap (MemPool->PciIo, MemBlock->Mapping);
+      }
+    }
+  }
 }
 
 
-- 
2.14.1.3.gb7cf6e02401b


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