From: "Laszlo Ersek" <lersek@redhat.com>
To: devel@edk2.groups.io, thomas.lendacky@amd.com
Cc: Jordan Justen <jordan.l.justen@intel.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: Re: [edk2-devel] [RFC PATCH v3 32/43] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Bypass flash detection with SEV-ES is enabled
Date: Thu, 21 Nov 2019 13:31:50 +0100 [thread overview]
Message-ID: <9a6a012c-9bdd-b3cb-65b3-79fda0158e88@redhat.com> (raw)
In-Reply-To: <c5640ef08609ec41192daf619a7048592135eaa3.1574280425.git.thomas.lendacky@amd.com>
On 11/20/19 21:06, Lendacky, Thomas wrote:
> 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.
(1) Please include the Bugzilla link in the commit message:
https://bugzilla.tianocore.org/show_bug.cgi?id=2198
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> OvmfPkg/OvmfPkgIa32.dsc | 1 +
> OvmfPkg/OvmfPkgIa32X64.dsc | 1 +
> OvmfPkg/OvmfPkgX64.dsc | 1 +
> .../FvbServicesRuntimeDxe.inf | 2 +
> .../QemuFlash.c | 38 +++++++++++++++++--
> 5 files changed, 40 insertions(+), 3 deletions(-)
>
> diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
> index 56670eefde6b..ff2814c6246e 100644
> --- a/OvmfPkg/OvmfPkgIa32.dsc
> +++ b/OvmfPkg/OvmfPkgIa32.dsc
> @@ -320,6 +320,7 @@ [LibraryClasses.common.DXE_RUNTIME_DRIVER]
> BaseCryptLib|CryptoPkg/Library/BaseCryptLib/RuntimeCryptLib.inf
> PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
> QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>
> [LibraryClasses.common.UEFI_DRIVER]
> PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf
> diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
> index 9897e6889573..212952cfaacd 100644
> --- a/OvmfPkg/OvmfPkgIa32X64.dsc
> +++ b/OvmfPkg/OvmfPkgIa32X64.dsc
> @@ -325,6 +325,7 @@ [LibraryClasses.common.DXE_RUNTIME_DRIVER]
> BaseCryptLib|CryptoPkg/Library/BaseCryptLib/RuntimeCryptLib.inf
> PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
> QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>
> [LibraryClasses.common.UEFI_DRIVER]
> PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf
> diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
> index 59c4f9207fc3..8331fc0b663e 100644
> --- a/OvmfPkg/OvmfPkgX64.dsc
> +++ b/OvmfPkg/OvmfPkgX64.dsc
> @@ -325,6 +325,7 @@ [LibraryClasses.common.DXE_RUNTIME_DRIVER]
> BaseCryptLib|CryptoPkg/Library/BaseCryptLib/RuntimeCryptLib.inf
> PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
> QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
> + VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>
> [LibraryClasses.common.UEFI_DRIVER]
> PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/FvbServicesRuntimeDxe.inf
> index ca6326e833ed..0b7741ac07f8 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
These hunks look good.
> diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> index c81c58972bf2..4f3bf690fcad 100644
> --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c
> @@ -9,7 +9,9 @@
>
> #include <Library/BaseMemoryLib.h>
> #include <Library/DebugLib.h>
> +#include <Library/MemEncryptSevLib.h>
> #include <Library/PcdLib.h>
> +#include <Library/VmgExitLib.h>
>
> #include "QemuFlash.h"
>
> @@ -80,6 +82,20 @@ 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 FD behaves as
> + // a ROM, the nested page table entry is read-only. The check below
(2) I suggest a slight change to the wording above. Please replace
when the FD behaves as a ROM
with
when the memslot is mapped read-only
(It's OK to make qemu / kvm references in this code: the name of the
file includes "Qemu".)
> + // will cause a nested page fault that cannot be emulated, causing
> + // the instruction to retried over and over. For SEV-ES, assume that
> + // the FD does not behave as FLASH.
(3) I would recommend
For SEV-ES, acknowledge that the FD appears as ROM and not as FLASH,
but report FLASH anyway.
> + //
> + DEBUG ((DEBUG_INFO,
> + "QEMU Flash: SEV-ES enabled, assuming FD behaves as FLASH\n"));
> + return TRUE;
> + }
> +
> OriginalUint8 = *Ptr;
> *Ptr = CLEAR_STATUS_CMD;
> ProbeUint8 = *Ptr;
> @@ -147,6 +163,21 @@ QemuFlashRead (
> }
>
>
> +STATIC
> +VOID
> +QemuFlashPtrWrite (
> + IN volatile UINT8 *Ptr,
> + IN UINT8 Value
> + )
> +{
> + if (MemEncryptSevEsIsEnabled()) {
> + VmgMmioWrite ((UINT8 *) Ptr, &Value, 1);
> + } else {
> + *Ptr = Value;
> + }
> +}
> +
> +
> /**
> Write to QEMU Flash
>
(4) This change will break the "FvbServicesSmm.inf" build of this module.
(Because, you have -- correctly -- added the VmgExitLib class to
"FvbServicesRuntimeDxe.inf" only.)
Please:
- create two implementations of the QemuFlashPtrWrite() function, one in
"QemuFlashDxe.c", and another in "QemuFlashSmm.c".
- the former should be the function shown above, the latter should only
perform the direct assignment.
- the '#include <Library/VmgExitLib.h>' directive should also be moved
to "QemuFlashDxe.c".
- the prototype for QemuFlashPtrWrite() should be added to "QemuFlash.h"
please.
> @@ -181,8 +212,9 @@ 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 +222,7 @@ QemuFlashWrite (
> // Restore flash to read mode
> //
> if (*NumBytes > 0) {
> - *(Ptr - 1) = READ_ARRAY_CMD;
> + QemuFlashPtrWrite (Ptr - 1, READ_ARRAY_CMD);
> }
>
> return EFI_SUCCESS;
>
With (1) and (4) fixed, and with (2) and (3) optionally fixed (i.e., if
you agree):
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Thanks
Laszlo
next prev parent reply other threads:[~2019-11-21 12:32 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 20:06 [RFC PATCH v3 00/43] SEV-ES guest support Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 01/43] MdePkg: Create PCDs to be used in support of SEV-ES Lendacky, Thomas
2019-12-12 6:53 ` Ni, Ray
2019-12-12 20:48 ` Lendacky, Thomas
2019-12-13 1:21 ` Ni, Ray
2019-11-20 20:06 ` [RFC PATCH v3 02/43] MdePkg: Add the MSR definition for the GHCB register Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 03/43] MdePkg: Add a structure definition for the GHCB Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 04/43] MdeModulePkg/DxeIplPeim: Support GHCB pages when creating page tables Lendacky, Thomas
2019-12-12 6:53 ` [edk2-devel] " Ni, Ray
2019-12-12 20:58 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 05/43] MdePkg/BaseLib: Add support for the XGETBV instruction Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 06/43] MdePkg/BaseLib: Add support for the VMGEXIT instruction Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 07/43] UefiCpuPkg: Implement library support for VMGEXIT Lendacky, Thomas
2019-11-21 11:15 ` [edk2-devel] " Laszlo Ersek
2019-11-21 16:48 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 08/43] UefiCpuPkg/CpuExceptionHandler: Add base support for the #VC exception Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 09/43] UefiCpuPkg/CpuExceptionHandler: Add support for IOIO_PROT NAE events Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 10/43] UefiCpuPkg/CpuExceptionHandler: Support string IO " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 11/43] UefiCpuPkg/CpuExceptionHandler: Add support for CPUID " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 12/43] UefiCpuPkg/CpuExceptionHandler: Add support for MSR_PROT " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 13/43] UefiCpuPkg/CpuExceptionHandler: Add support for NPF NAE events (MMIO) Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 14/43] UefiCpuPkg/CpuExceptionHandler: Add support for WBINVD NAE events Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 15/43] UefiCpuPkg/CpuExceptionHandler: Add support for RDTSC " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 16/43] UefiCpuPkg/CpuExceptionHandler: Add support for RDPMC " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 17/43] UefiCpuPkg/CpuExceptionHandler: Add support for INVD " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 18/43] UefiCpuPkg/CpuExceptionHandler: Add support for VMMCALL " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 19/43] UefiCpuPkg/CpuExceptionHandler: Add support for RDTSCP " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 20/43] UefiCpuPkg/CpuExceptionHandler: Add support for MONITOR/MONITORX " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 21/43] UefiCpuPkg/CpuExceptionHandler: Add support for MWAIT/MWAITX " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 22/43] UefiCpuPkg/CpuExceptionHandler: Add support for DR7 Read/Write " Lendacky, Thomas
2019-12-12 6:53 ` Ni, Ray
2019-12-12 20:39 ` Lendacky, Thomas
2019-12-12 6:53 ` Ni, Ray
2019-12-12 20:27 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 23/43] OvmfPkg/MemEncryptSevLib: Add an SEV-ES guest indicator function Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 24/43] OvmfPkg: Add support to perform SEV-ES initialization Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 25/43] OvmfPkg/ResetVector: Add support for a 32-bit SEV check Lendacky, Thomas
2019-11-21 11:02 ` [edk2-devel] " Laszlo Ersek
2019-11-20 20:06 ` [RFC PATCH v3 26/43] OvmfPkg: Create a GHCB page for use during Sec phase Lendacky, Thomas
2019-11-21 11:29 ` [edk2-devel] " Laszlo Ersek
2019-11-20 20:06 ` [RFC PATCH v3 27/43] OvmfPkg/PlatformPei: Reserve GHCB-related areas if S3 is supported Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 28/43] OvmfPkg: Create GHCB pages for use during Pei and Dxe phase Lendacky, Thomas
2019-12-12 6:54 ` Ni, Ray
2019-12-12 21:03 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 29/43] OvmfPkg/PlatformPei: Move early GDT into ram when SEV-ES is enabled Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 30/43] OvmfPkg/Sec: Add #VC exception handling for Sec phase Lendacky, Thomas
2019-11-21 12:06 ` [edk2-devel] " Laszlo Ersek
2019-11-21 20:46 ` Lendacky, Thomas
2019-11-22 12:52 ` Laszlo Ersek
2019-11-22 16:30 ` Lendacky, Thomas
2019-11-22 21:10 ` Laszlo Ersek
2019-11-22 22:48 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 31/43] OvmfPkg/Sec: Enable cache early to speed up booting Lendacky, Thomas
2019-11-21 12:08 ` [edk2-devel] " Laszlo Ersek
2019-11-20 20:06 ` [RFC PATCH v3 32/43] OvmfPkg/QemuFlashFvbServicesRuntimeDxe: Bypass flash detection with SEV-ES is enabled Lendacky, Thomas
2019-11-21 12:31 ` Laszlo Ersek [this message]
2019-11-21 21:11 ` [edk2-devel] " Lendacky, Thomas
2019-11-22 12:20 ` Laszlo Ersek
2019-11-20 20:06 ` [RFC PATCH v3 33/43] MdeModulePkg: Reserve a 16-bit protected mode code segment descriptor Lendacky, Thomas
2019-12-12 6:57 ` Ni, Ray
2019-12-12 21:19 ` [edk2-devel] " Lendacky, Thomas
2019-12-13 1:20 ` Ni, Ray
2019-11-20 20:06 ` [RFC PATCH v3 34/43] UefiCpuPkg: Add " Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 35/43] UefiCpuPkg/MpInitLib: Add a CPU MP data flag to indicate if SEV-ES is enabled Lendacky, Thomas
2019-12-12 7:01 ` Ni, Ray
2019-12-12 21:21 ` Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 36/43] UefiCpuPkg: Allow AP booting under SEV-ES Lendacky, Thomas
2019-11-20 20:06 ` [RFC PATCH v3 37/43] OvmfPkg: Reserve a page in memory for the SEV-ES AP reset vector Lendacky, Thomas
2019-11-21 19:27 ` [edk2-devel] " Laszlo Ersek
2019-11-21 22:49 ` Lendacky, Thomas
2019-11-22 16:06 ` Laszlo Ersek
2019-11-22 16:40 ` Lendacky, Thomas
2019-11-20 20:07 ` [RFC PATCH v3 38/43] OvmfPkg: Move the GHCB allocations into reserved memory Lendacky, Thomas
2019-11-20 20:07 ` [RFC PATCH v3 39/43] MdePkg: Add a finalization function to the CPU protocol Lendacky, Thomas
2019-11-20 21:32 ` [RFC PATCH v3 40/43] UefiCpuPkg/MpInitLib: Add MP finalization interface to MpInitLib Lendacky, Thomas
2019-11-20 21:32 ` [RFC PATCH v3 41/43] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use Lendacky, Thomas
2019-11-20 21:32 ` [RFC PATCH v3 42/43] UefiCpuPkg/CpuDxe: Provide an DXE MP finalization routine to support SEV-ES Lendacky, Thomas
2019-11-20 21:32 ` [RFC PATCH v3 43/43] MdeModulePkg/DxeCore: Perform the CPU protocol finalization support Lendacky, Thomas
2019-11-21 1:53 ` [edk2-devel] [RFC PATCH v3 00/43] SEV-ES guest support Nate DeSimone
2019-11-21 15:50 ` Lendacky, Thomas
2019-11-21 9:45 ` Laszlo Ersek
2019-11-21 9:48 ` Laszlo Ersek
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