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From: "Lendacky, Thomas" <thomas.lendacky@amd.com>
To: devel@edk2.groups.io
Cc: Jordan Justen <jordan.l.justen@intel.com>,
	Laszlo Ersek <lersek@redhat.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Michael D Kinney <michael.d.kinney@intel.com>,
	Liming Gao <liming.gao@intel.com>,
	Eric Dong <eric.dong@intel.com>, Ray Ni <ray.ni@intel.com>,
	Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH v6 36/42] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Bypass flash detection with SEV-ES is enabled
Date: Tue, 24 Mar 2020 12:40:50 -0500	[thread overview]
Message-ID: <343eccd736a9c86060f59eaff5c1bc85ebeb9ad7.1585071656.git.thomas.lendacky@amd.com> (raw)
In-Reply-To: <cover.1585071656.git.thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

The flash detection routine will attempt to determine how the flash
device behaves (e.g. ROM, RAM, Flash). But when SEV-ES is enabled and
the flash device behaves as a ROM device (meaning it is marked read-only
by the hypervisor), this check may result in an infinite nested page fault
because of the attempted write. Since the instruction cannot be emulated
when SEV-ES is enabled, the RIP is never advanced, resulting in repeated
nested page faults.

When SEV-ES is enabled, exit the flash detection early and assume that
the FD behaves as Flash. This will result in QemuFlashWrite() being called
to store EFI variables, which will also result in an infinite nested page
fault when the write is performed. In this case, update QemuFlashWrite()
to use the VmgMmioWrite function from the VmgExitLib library to have the
hypervisor perform the write without having to emulate the instruction.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 .../FvbServicesRuntimeDxe.inf                 |  2 ++
 .../QemuFlash.h                               |  6 +++++
 .../QemuFlash.c                               | 23 ++++++++++++++++---
 .../QemuFlashDxe.c                            | 15 ++++++++++++
 .../QemuFlashSmm.c                            |  9 ++++++++
 5 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
index 72cabba4357d..8bb2325157ea 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
@@ -38,6 +38,7 @@ [Sources]
 [Packages]
   MdePkg/MdePkg.dec
   MdeModulePkg/MdeModulePkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
   OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
@@ -52,6 +53,7 @@ [LibraryClasses]
   UefiBootServicesTableLib
   UefiDriverEntryPoint
   UefiRuntimeLib
+  VmgExitLib
 
 [Guids]
   gEfiEventVirtualAddressChangeGuid   # ALWAYS_CONSUMED
diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
index f1afabcbe6ae..19ac1f733279 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.h
@@ -89,5 +89,11 @@ QemuFlashBeforeProbe (
   IN  UINTN                   FdBlockCount
   );
 
+VOID
+QemuFlashPtrWrite (
+  IN        volatile UINT8    *Ptr,
+  IN        UINT8             Value
+  );
+
 #endif
 
diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
index c81c58972bf2..358bce3336f2 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
@@ -9,6 +9,7 @@
 
 #include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
+#include <Library/MemEncryptSevLib.h>
 #include <Library/PcdLib.h>
 
 #include "QemuFlash.h"
@@ -80,6 +81,21 @@ QemuFlashDetected (
 
   DEBUG ((EFI_D_INFO, "QEMU Flash: Attempting flash detection at %p\n", Ptr));
 
+  if (MemEncryptSevEsIsEnabled ()) {
+    //
+    // When SEV-ES is enabled, the check below can result in an infinite
+    // loop with respect to a nested page fault. When the memslot is mapped
+    // read-only, the nested page table entry is read-only. The check below
+    // will cause a nested page fault that cannot be emulated, causing
+    // the instruction to retried over and over. For SEV-ES, acknowledge that
+    // the FD appears as ROM and not as FLASH, but report FLASH anyway because
+    // FLASH behavior can be simulated using VMGEXIT.
+    //
+    DEBUG ((DEBUG_INFO,
+      "QEMU Flash: SEV-ES enabled, assuming FD behaves as FLASH\n"));
+    return TRUE;
+  }
+
   OriginalUint8 = *Ptr;
   *Ptr = CLEAR_STATUS_CMD;
   ProbeUint8 = *Ptr;
@@ -181,8 +197,9 @@ QemuFlashWrite (
   //
   Ptr = QemuFlashPtr (Lba, Offset);
   for (Loop = 0; Loop < *NumBytes; Loop++) {
-    *Ptr = WRITE_BYTE_CMD;
-    *Ptr = Buffer[Loop];
+    QemuFlashPtrWrite (Ptr, WRITE_BYTE_CMD);
+    QemuFlashPtrWrite (Ptr, Buffer[Loop]);
+
     Ptr++;
   }
 
@@ -190,7 +207,7 @@ QemuFlashWrite (
   // Restore flash to read mode
   //
   if (*NumBytes > 0) {
-    *(Ptr - 1) = READ_ARRAY_CMD;
+    QemuFlashPtrWrite (Ptr - 1, READ_ARRAY_CMD);
   }
 
   return EFI_SUCCESS;
diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
index 5aabe9d7b59c..83856f575083 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashDxe.c
@@ -10,6 +10,8 @@
 **/
 
 #include <Library/UefiRuntimeLib.h>
+#include <Library/MemEncryptSevLib.h>
+#include <Library/VmgExitLib.h>
 
 #include "QemuFlash.h"
 
@@ -32,3 +34,16 @@ QemuFlashBeforeProbe (
   // Do nothing
   //
 }
+
+VOID
+QemuFlashPtrWrite (
+  IN        volatile UINT8    *Ptr,
+  IN        UINT8             Value
+  )
+{
+  if (MemEncryptSevEsIsEnabled ()) {
+    VmgMmioWrite ((UINT8 *) Ptr, &Value, 1);
+  } else {
+    *Ptr = Value;
+  }
+}
diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c
index 7eb426e03855..eff40ae28032 100644
--- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c
+++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c
@@ -46,3 +46,12 @@ QemuFlashBeforeProbe (
              );
   ASSERT_EFI_ERROR (Status);
 }
+
+VOID
+QemuFlashPtrWrite (
+  IN        volatile UINT8    *Ptr,
+  IN        UINT8             Value
+  )
+{
+  *Ptr = Value;
+}
-- 
2.17.1


  parent reply	other threads:[~2020-03-24 17:42 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 17:40 [PATCH v6 00/42] SEV-ES guest support Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 01/42] MdePkg: Create PCDs to be used in support of SEV-ES Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 02/42] MdePkg: Add the MSR definition for the GHCB register Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 03/42] MdePkg: Add a structure definition for the GHCB Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 04/42] MdeModulePkg/DxeIplPeim: Support GHCB pages when creating page tables Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 05/42] MdePkg/BaseLib: Add support for the XGETBV instruction Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 06/42] MdePkg/BaseLib: Add support for the VMGEXIT instruction Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 07/42] UefiCpuPkg: Implement library support for VMGEXIT Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 08/42] OvmfPkg: Prepare OvmfPkg to use the VmgExitLib library Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 09/42] UefiPayloadPkg: Prepare UefiPayloadPkg " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 10/42] UefiCpuPkg/CpuExceptionHandler: Add base support for the #VC exception Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 11/42] UefiCpuPkg/CpuExceptionHandler: Add support for IOIO_PROT NAE events Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 12/42] UefiCpuPkg/CpuExceptionHandler: Support string IO " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 13/42] UefiCpuPkg/CpuExceptionHandler: Add support for CPUID " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 14/42] UefiCpuPkg/CpuExceptionHandler: Add support for MSR_PROT " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 15/42] UefiCpuPkg/CpuExceptionHandler: Add support for NPF NAE events (MMIO) Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 16/42] UefiCpuPkg/CpuExceptionHandler: Add support for WBINVD NAE events Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 17/42] UefiCpuPkg/CpuExceptionHandler: Add support for RDTSC " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 18/42] UefiCpuPkg/CpuExceptionHandler: Add support for RDPMC " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 19/42] UefiCpuPkg/CpuExceptionHandler: Add support for INVD " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 20/42] UefiCpuPkg/CpuExceptionHandler: Add support for VMMCALL " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 21/42] UefiCpuPkg/CpuExceptionHandler: Add support for RDTSCP " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 22/42] UefiCpuPkg/CpuExceptionHandler: Add support for MONITOR/MONITORX " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 23/42] UefiCpuPkg/CpuExceptionHandler: Add support for MWAIT/MWAITX " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 24/42] UefiCpuPkg/CpuExceptionHandler: Add support for DR7 Read/Write " Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 25/42] OvmfPkg/MemEncryptSevLib: Add an SEV-ES guest indicator function Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 26/42] OvmfPkg: Add support to perform SEV-ES initialization Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 27/42] OvmfPkg: Create a GHCB page for use during Sec phase Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 28/42] OvmfPkg/PlatformPei: Reserve GHCB-related areas if S3 is supported Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 29/42] OvmfPkg: Create GHCB pages for use during Pei and Dxe phase Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 30/42] OvmfPkg/PlatformPei: Move early GDT into ram when SEV-ES is enabled Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 31/42] UefiCpuPkg: Create an SEV-ES workarea PCD Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 32/42] OvmfPkg: Reserve a page in memory for the SEV-ES usage Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 33/42] OvmfPkg/ResetVector: Add support for a 32-bit SEV check Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 34/42] OvmfPkg/Sec: Add #VC exception handling for Sec phase Lendacky, Thomas
2020-03-24 17:40 ` Lendacky, Thomas [this message]
2020-03-24 17:40 ` [PATCH v6 37/42] UefiCpuPkg: Add a 16-bit protected mode code segment descriptor Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 38/42] UefiCpuPkg/MpInitLib: Add CPU MP data flag to indicate if SEV-ES is enabled Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 39/42] UefiCpuPkg: Allow AP booting under SEV-ES Lendacky, Thomas
2020-03-24 17:40 ` [PATCH v6 40/42] OvmfPkg: Use the SEV-ES work area for the SEV-ES AP reset vector Lendacky, Thomas
2020-03-24 19:44 ` [PATCH v6 35/42] OvmfPkg/Sec: Enable cache early to speed up booting Lendacky, Thomas
2020-03-24 19:44 ` [PATCH v6 41/42] OvmfPkg: Move the GHCB allocations into reserved memory Lendacky, Thomas
2020-03-24 19:44 ` [PATCH v6 42/42] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use Lendacky, Thomas
2020-03-30 16:53 ` [PATCH v6 00/42] SEV-ES guest support Lendacky, Thomas
2020-03-31  0:47   ` [edk2-devel] " Dong, Eric
2020-04-01 20:42     ` Lendacky, Thomas
2020-04-02  0:12       ` Dong, Eric
     [not found]       ` <1601D84A636A7BFC.25844@groups.io>
2020-04-14 15:30         ` Dong, Eric
2020-04-16 13:46           ` Lendacky, Thomas
2020-04-17  9:10             ` Dong, Eric

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