* [PATCH v1 0/2] Add support to disable VirtIo net at runtime
@ 2022-08-04 2:52 Yuan Yu
2022-08-04 2:52 ` [PATCH v1 1/2] OvmfPkg: Introduce NetworkCfgLib Yuan Yu
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Yuan Yu @ 2022-08-04 2:52 UTC (permalink / raw)
To: devel
Cc: Ard Biesheuvel, Jordan Justen, Laszlo Ersek, Anthony Perard,
Julien Grall
Currently networking can only be enabled/disabled at compile time. This
patch series will add support to disable VirtIo net at runtime even if
the functionality is built into binary at compile time.
This will enable VMM to reduce attack surface without recompilation.
The changes can be seen at:
https://github.com/yyu/edk2/tree/network_cfg_lib_v1
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Yuan Yu (2):
OvmfPkg: Introduce NetworkCfgLib
OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net
OvmfPkg/OvmfPkg.dec | 3 ++
OvmfPkg/OvmfPkgX64.dsc | 7 ++++-
OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf | 29 ++++++++++++++++++
OvmfPkg/VirtioNetDxe/VirtioNet.inf | 3 ++
OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c | 32 ++++++++++++++++++++
OvmfPkg/VirtioNetDxe/EntryPoint.c | 10 ++++++
6 files changed, 83 insertions(+), 1 deletion(-)
create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf
create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c
--
2.37.1.559.g78731f0fdb-goog
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v1 1/2] OvmfPkg: Introduce NetworkCfgLib 2022-08-04 2:52 [PATCH v1 0/2] Add support to disable VirtIo net at runtime Yuan Yu @ 2022-08-04 2:52 ` Yuan Yu 2022-08-04 2:52 ` [PATCH v1 2/2] OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net Yuan Yu 2022-08-04 5:55 ` [PATCH v1 0/2] Add support to disable VirtIo net at runtime Laszlo Ersek 2 siblings, 0 replies; 6+ messages in thread From: Yuan Yu @ 2022-08-04 2:52 UTC (permalink / raw) To: devel Cc: Ard Biesheuvel, Jordan Justen, Laszlo Ersek, Anthony Perard, Julien Grall Introduce NetworkCfgLib which will set PcdNetworkSupport based on "etc/networking" qemu file. If "etc/networking" (type bool) is TRUE, then PcdNetworkSupport will be TRUE and vice versa. In the following patch, PcdNetworkSupport will be used to enable/disable VirtIo net driver so that VMM will have control over networking functionality in runtime. The default value of PcdNetworkSupport is TRUE, which means if network support is turned on at compile time and VMM doesn't do anything, the VirtIo driver will be enabled. This is to make it consistent with the behavior before this patch. Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Anthony Perard <anthony.perard@citrix.com> Cc: Julien Grall <julien@xen.org> Signed-off-by: Yuan Yu <yuanyu@google.com> --- OvmfPkg/OvmfPkg.dec | 3 ++ OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf | 29 ++++++++++++++++++ OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c | 32 ++++++++++++++++++++ 3 files changed, 64 insertions(+) diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec index 5af76a540529..5dced0568f6c 100644 --- a/OvmfPkg/OvmfPkg.dec +++ b/OvmfPkg/OvmfPkg.dec @@ -451,6 +451,9 @@ [PcdsDynamic, PcdsDynamicEx] ## This PCD records LASA field in CC EVENTLOG ACPI table. gUefiOvmfPkgTokenSpaceGuid.PcdCcEventlogAcpiTableLasa|0|UINT64|0x67 + ## This PCD controls if network support should be turned on at runtime. + gUefiOvmfPkgTokenSpaceGuid.PcdNetworkSupport|TRUE|BOOLEAN|0x72 + [PcdsFeatureFlag] gUefiOvmfPkgTokenSpaceGuid.PcdQemuBootOrderPciTranslation|TRUE|BOOLEAN|0x1c gUefiOvmfPkgTokenSpaceGuid.PcdQemuBootOrderMmioTranslation|FALSE|BOOLEAN|0x1d diff --git a/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf b/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf new file mode 100644 index 000000000000..44be171ccc7a --- /dev/null +++ b/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf @@ -0,0 +1,29 @@ +## @file +# Configure some PCDs dynamically +# +# SPDX-License-Identifier: BSD-2-Clause-Patent +## + +[Defines] + INF_VERSION = 1.27 + BASE_NAME = NetworkCfgLib + FILE_GUID = c81bfcf9-7dce-44f7-a9cb-be607f481a86 + MODULE_TYPE = BASE + VERSION_STRING = 1.0 + LIBRARY_CLASS = NULL + CONSTRUCTOR = SetNetworkingSupportPcds + +[Sources] + NetworkCfgLib.c + +[Packages] + MdePkg/MdePkg.dec + OvmfPkg/OvmfPkg.dec + +[LibraryClasses] + PcdLib + DebugLib + QemuFwCfgSimpleParserLib + +[Pcd] + gUefiOvmfPkgTokenSpaceGuid.PcdNetworkSupport ## SOMETIMES_PRODUCES diff --git a/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c b/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c new file mode 100644 index 000000000000..e77198dbd4e4 --- /dev/null +++ b/OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c @@ -0,0 +1,32 @@ +#include <Library/PcdLib.h> +#include <Library/DebugLib.h> +#include <Library/QemuFwCfgSimpleParserLib.h> + +RETURN_STATUS +EFIAPI +SetNetworkingSupportPcds ( + VOID + ) +{ + BOOLEAN FwCfgBool; + RETURN_STATUS Status; + + DEBUG ((DEBUG_INFO, "[network] %a\n", __FUNCTION__)); + + Status = QemuFwCfgParseBool ("etc/networking", &FwCfgBool); + if (RETURN_ERROR (Status)) { + DEBUG ((DEBUG_INFO, + "[network] QemuFwCfgParseBool('etc/networking') failed, will return " + "SUCCESS and continue without overriding PcdNetworkSupport.\n")); + return RETURN_SUCCESS; + } + DEBUG ((DEBUG_INFO, "[network] etc/networking = %d\n", FwCfgBool)); + + Status = PcdSetBoolS (PcdNetworkSupport, FwCfgBool); + if (RETURN_ERROR (Status)) { + return Status; + } + DEBUG ((DEBUG_INFO, "[network] PcdNetworkSupport was set to %d\n", FwCfgBool)); + + return RETURN_SUCCESS; +} -- 2.37.1.559.g78731f0fdb-goog ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v1 2/2] OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net 2022-08-04 2:52 [PATCH v1 0/2] Add support to disable VirtIo net at runtime Yuan Yu 2022-08-04 2:52 ` [PATCH v1 1/2] OvmfPkg: Introduce NetworkCfgLib Yuan Yu @ 2022-08-04 2:52 ` Yuan Yu 2022-08-04 5:55 ` [PATCH v1 0/2] Add support to disable VirtIo net at runtime Laszlo Ersek 2 siblings, 0 replies; 6+ messages in thread From: Yuan Yu @ 2022-08-04 2:52 UTC (permalink / raw) To: devel Cc: Ard Biesheuvel, Jordan Justen, Laszlo Ersek, Anthony Perard, Julien Grall Enable/Disable VirtIo net based on the value of PcdNetworkSupport which is controlled in NetworkCfgLib, which sets the PCD based on "etc/networking" qemu file. With this change, VMM can disable networking even if it is enabled at compile time. This will allow to reduce attack surface by simply providing an "etc/networking" value without having to recompile EDK2 completely. Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> Cc: Jordan Justen <jordan.l.justen@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Cc: Anthony Perard <anthony.perard@citrix.com> Cc: Julien Grall <julien@xen.org> Signed-off-by: Yuan Yu <yuanyu@google.com> --- OvmfPkg/OvmfPkgX64.dsc | 7 ++++++- OvmfPkg/VirtioNetDxe/VirtioNet.inf | 3 +++ OvmfPkg/VirtioNetDxe/EntryPoint.c | 10 ++++++++++ 3 files changed, 19 insertions(+), 1 deletion(-) diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc index 6e68f60dc90f..63cce9f65a95 100644 --- a/OvmfPkg/OvmfPkgX64.dsc +++ b/OvmfPkg/OvmfPkgX64.dsc @@ -686,6 +686,8 @@ [PcdsDynamicDefault] gEfiMdePkgTokenSpaceGuid.PcdFSBClock|1000000000 !endif + gUefiOvmfPkgTokenSpaceGuid.PcdNetworkSupport|TRUE + [PcdsDynamicHii] !include OvmfPkg/OvmfTpmPcdsHii.dsc.inc @@ -953,7 +955,10 @@ [Components] NULL|OvmfPkg/Library/TlsAuthConfigLib/TlsAuthConfigLib.inf } !endif - OvmfPkg/VirtioNetDxe/VirtioNet.inf + OvmfPkg/VirtioNetDxe/VirtioNet.inf { + <LibraryClasses> + NULL|OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf + } # # Usb Support diff --git a/OvmfPkg/VirtioNetDxe/VirtioNet.inf b/OvmfPkg/VirtioNetDxe/VirtioNet.inf index ada84ed5543b..37bcf13b7863 100644 --- a/OvmfPkg/VirtioNetDxe/VirtioNet.inf +++ b/OvmfPkg/VirtioNetDxe/VirtioNet.inf @@ -54,3 +54,6 @@ [Protocols] gEfiSimpleNetworkProtocolGuid ## BY_START gEfiDevicePathProtocolGuid ## BY_START gVirtioDeviceProtocolGuid ## TO_START + +[Pcd] + gUefiOvmfPkgTokenSpaceGuid.PcdNetworkSupport ## CONSUMES diff --git a/OvmfPkg/VirtioNetDxe/EntryPoint.c b/OvmfPkg/VirtioNetDxe/EntryPoint.c index c3f41dab57bd..9bf220b9ade5 100644 --- a/OvmfPkg/VirtioNetDxe/EntryPoint.c +++ b/OvmfPkg/VirtioNetDxe/EntryPoint.c @@ -9,6 +9,8 @@ **/ +#include <PiDxe.h> + #include <Library/UefiLib.h> #include "VirtioNet.h" @@ -32,6 +34,14 @@ VirtioNetEntryPoint ( IN EFI_SYSTEM_TABLE *SystemTable ) { + if (PcdGetBool (PcdNetworkSupport)) { + DEBUG ((DEBUG_INFO, "[network] %a - Networking enabled.\n", __FUNCTION__)); + } else { + DEBUG ((DEBUG_INFO, "[network] %a - Networking disabled.\n", __FUNCTION__)); + + return EFI_REQUEST_UNLOAD_IMAGE; + } + return EfiLibInstallDriverBindingComponentName2 ( ImageHandle, SystemTable, -- 2.37.1.559.g78731f0fdb-goog ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v1 0/2] Add support to disable VirtIo net at runtime 2022-08-04 2:52 [PATCH v1 0/2] Add support to disable VirtIo net at runtime Yuan Yu 2022-08-04 2:52 ` [PATCH v1 1/2] OvmfPkg: Introduce NetworkCfgLib Yuan Yu 2022-08-04 2:52 ` [PATCH v1 2/2] OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net Yuan Yu @ 2022-08-04 5:55 ` Laszlo Ersek 2022-08-04 9:58 ` [edk2-devel] " Ard Biesheuvel 2 siblings, 1 reply; 6+ messages in thread From: Laszlo Ersek @ 2022-08-04 5:55 UTC (permalink / raw) To: Yuan Yu, devel Cc: Ard Biesheuvel, Jordan Justen, Anthony Perard, Julien Grall, Gerd Hoffmann, Pawel Polawski, Oliver Steffen, Jiewen Yao On 08/04/22 04:52, Yuan Yu wrote: > Currently networking can only be enabled/disabled at compile time. This > patch series will add support to disable VirtIo net at runtime even if > the functionality is built into binary at compile time. > > This will enable VMM to reduce attack surface without recompilation. > > The changes can be seen at: > https://github.com/yyu/edk2/tree/network_cfg_lib_v1 > > Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> > Cc: Jordan Justen <jordan.l.justen@intel.com> > Cc: Laszlo Ersek <lersek@redhat.com> > Cc: Anthony Perard <anthony.perard@citrix.com> > Cc: Julien Grall <julien@xen.org> > > Yuan Yu (2): > OvmfPkg: Introduce NetworkCfgLib > OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net > > OvmfPkg/OvmfPkg.dec | 3 ++ > OvmfPkg/OvmfPkgX64.dsc | 7 ++++- > OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf | 29 ++++++++++++++++++ > OvmfPkg/VirtioNetDxe/VirtioNet.inf | 3 ++ > OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c | 32 ++++++++++++++++++++ > OvmfPkg/VirtioNetDxe/EntryPoint.c | 10 ++++++ > 6 files changed, 83 insertions(+), 1 deletion(-) > create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf > create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c > Well I've not been reviewing upstream edk2 patches for a while, but the virtio-net driver is still very close to my heart, so this patch kind of hits a nerve. I think I disagree with the idea and the implementation both. Minimally, the idea needs a much better elaboration -- what is the threat model? Do you want to protect the host from the guest, or the guest from the host? Or something else? How does controlling a single SNP driver via fw_cfg (which is also dictated by the host) help? Regarding the implementation: there is much more to networking in edk2 than VirtioNetDxe. UEFI driver binaries (SNP drivers) built from iPXE can be passed in via the NICs' option ROMs. SNP drivers can be loaded from the UEFI system partition (for example, Intel's binary-only driver for QEMU's e1000* cards). If you can control this fw_cfg switch from the VMM side, you can also control the VMM enough to simply *not give* a virtio-net device to the guest. Then the driver (it being a UEFI driver following the UEFI driver model) will simply not have anything to bind. Sorry I find this approach very wrong. If you really need it for your particular VMM, I kind of suggest not upstreaming this patch. I see it as a step backwards for the upstream project. Anyway: I emphasize I'm no longer a reviewer for OvmfPkg, and it's quite exceptional that I'm reacting at all to being CC'd on this. Laszlo ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [edk2-devel] [PATCH v1 0/2] Add support to disable VirtIo net at runtime 2022-08-04 5:55 ` [PATCH v1 0/2] Add support to disable VirtIo net at runtime Laszlo Ersek @ 2022-08-04 9:58 ` Ard Biesheuvel 2022-08-04 10:54 ` Laszlo Ersek 0 siblings, 1 reply; 6+ messages in thread From: Ard Biesheuvel @ 2022-08-04 9:58 UTC (permalink / raw) To: edk2-devel-groups-io, Laszlo Ersek Cc: Yuan Yu, Ard Biesheuvel, Jordan Justen, Anthony Perard, Julien Grall, Gerd Hoffmann, Pawel Polawski, Oliver Steffen, Jiewen Yao On Thu, 4 Aug 2022 at 07:55, Laszlo Ersek <lersek@redhat.com> wrote: > > On 08/04/22 04:52, Yuan Yu wrote: > > Currently networking can only be enabled/disabled at compile time. This > > patch series will add support to disable VirtIo net at runtime even if > > the functionality is built into binary at compile time. > > > > This will enable VMM to reduce attack surface without recompilation. > > > > The changes can be seen at: > > https://github.com/yyu/edk2/tree/network_cfg_lib_v1 > > > > Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> > > Cc: Jordan Justen <jordan.l.justen@intel.com> > > Cc: Laszlo Ersek <lersek@redhat.com> > > Cc: Anthony Perard <anthony.perard@citrix.com> > > Cc: Julien Grall <julien@xen.org> > > > > Yuan Yu (2): > > OvmfPkg: Introduce NetworkCfgLib > > OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net > > > > OvmfPkg/OvmfPkg.dec | 3 ++ > > OvmfPkg/OvmfPkgX64.dsc | 7 ++++- > > OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf | 29 ++++++++++++++++++ > > OvmfPkg/VirtioNetDxe/VirtioNet.inf | 3 ++ > > OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c | 32 ++++++++++++++++++++ > > OvmfPkg/VirtioNetDxe/EntryPoint.c | 10 ++++++ > > 6 files changed, 83 insertions(+), 1 deletion(-) > > create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf > > create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c > > > > Well I've not been reviewing upstream edk2 patches for a while, but the > virtio-net driver is still very close to my heart, so this patch kind of > hits a nerve. > Welcome back old friend! > I think I disagree with the idea and the implementation both. > > Minimally, the idea needs a much better elaboration -- what is the > threat model? Do you want to protect the host from the guest, or the > guest from the host? Or something else? How does controlling a single > SNP driver via fw_cfg (which is also dictated by the host) help? > I have to confess that I was the one who suggested this approach to Yuan internally, but mainly to get the discussion going, as I was anticipating some pushback, just not from you :-) 'Reducing the attack surface' is probably not the most accurate characterization of the purpose. We are simply looking for a way to disable network boot from the vmm/host side without affecting how/which network interfaces the guest exposes to the OS. > Regarding the implementation: there is much more to networking in edk2 > than VirtioNetDxe. UEFI driver binaries (SNP drivers) built from iPXE > can be passed in via the NICs' option ROMs. SNP drivers can be loaded > from the UEFI system partition (for example, Intel's binary-only driver > for QEMU's e1000* cards). > > If you can control this fw_cfg switch from the VMM side, you can also > control the VMM enough to simply *not give* a virtio-net device to the > guest. Then the driver (it being a UEFI driver following the UEFI driver > model) will simply not have anything to bind. > Sure, but then the OS will lose networking as well. We just want to remove the ability to network boot without impacting anything else that relies on virtio-net > Sorry I find this approach very wrong. If you really need it for your > particular VMM, I kind of suggest not upstreaming this patch. I see it > as a step backwards for the upstream project. > If there are better ways to achieve this, we're all ears, but I think that having a PCD which could either be fixed at build and compiled out completely, or be set via a NULL library resolution, or even be wired to a menu option (using PcdsDynamicHii] is a rather low-impact but flexible way to go about this. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [edk2-devel] [PATCH v1 0/2] Add support to disable VirtIo net at runtime 2022-08-04 9:58 ` [edk2-devel] " Ard Biesheuvel @ 2022-08-04 10:54 ` Laszlo Ersek 0 siblings, 0 replies; 6+ messages in thread From: Laszlo Ersek @ 2022-08-04 10:54 UTC (permalink / raw) To: Ard Biesheuvel, edk2-devel-groups-io Cc: Yuan Yu, Ard Biesheuvel, Jordan Justen, Anthony Perard, Julien Grall, Gerd Hoffmann, Pawel Polawski, Oliver Steffen, Jiewen Yao On 08/04/22 11:58, Ard Biesheuvel wrote: > On Thu, 4 Aug 2022 at 07:55, Laszlo Ersek <lersek@redhat.com> wrote: >> >> On 08/04/22 04:52, Yuan Yu wrote: >>> Currently networking can only be enabled/disabled at compile time. This >>> patch series will add support to disable VirtIo net at runtime even if >>> the functionality is built into binary at compile time. >>> >>> This will enable VMM to reduce attack surface without recompilation. >>> >>> The changes can be seen at: >>> https://github.com/yyu/edk2/tree/network_cfg_lib_v1 >>> >>> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> >>> Cc: Jordan Justen <jordan.l.justen@intel.com> >>> Cc: Laszlo Ersek <lersek@redhat.com> >>> Cc: Anthony Perard <anthony.perard@citrix.com> >>> Cc: Julien Grall <julien@xen.org> >>> >>> Yuan Yu (2): >>> OvmfPkg: Introduce NetworkCfgLib >>> OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net >>> >>> OvmfPkg/OvmfPkg.dec | 3 ++ >>> OvmfPkg/OvmfPkgX64.dsc | 7 ++++- >>> OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf | 29 ++++++++++++++++++ >>> OvmfPkg/VirtioNetDxe/VirtioNet.inf | 3 ++ >>> OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c | 32 ++++++++++++++++++++ >>> OvmfPkg/VirtioNetDxe/EntryPoint.c | 10 ++++++ >>> 6 files changed, 83 insertions(+), 1 deletion(-) >>> create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.inf >>> create mode 100644 OvmfPkg/Library/NetworkCfgLib/NetworkCfgLib.c >>> >> >> Well I've not been reviewing upstream edk2 patches for a while, but the >> virtio-net driver is still very close to my heart, so this patch kind of >> hits a nerve. >> > > Welcome back old friend! > >> I think I disagree with the idea and the implementation both. >> >> Minimally, the idea needs a much better elaboration -- what is the >> threat model? Do you want to protect the host from the guest, or the >> guest from the host? Or something else? How does controlling a single >> SNP driver via fw_cfg (which is also dictated by the host) help? >> > > I have to confess that I was the one who suggested this approach to > Yuan internally, but mainly to get the discussion going, as I was > anticipating some pushback, just not from you :-) Heh, sorry about that :) > > 'Reducing the attack surface' is probably not the most accurate > characterization of the purpose. We are simply looking for a way to > disable network boot from the vmm/host side without affecting > how/which network interfaces the guest exposes to the OS. > >> Regarding the implementation: there is much more to networking in edk2 >> than VirtioNetDxe. UEFI driver binaries (SNP drivers) built from iPXE >> can be passed in via the NICs' option ROMs. SNP drivers can be loaded >> from the UEFI system partition (for example, Intel's binary-only driver >> for QEMU's e1000* cards). >> >> If you can control this fw_cfg switch from the VMM side, you can also >> control the VMM enough to simply *not give* a virtio-net device to the >> guest. Then the driver (it being a UEFI driver following the UEFI driver >> model) will simply not have anything to bind. >> > > Sure, but then the OS will lose networking as well. We just want to > remove the ability to network boot without impacting anything else > that relies on virtio-net > >> Sorry I find this approach very wrong. If you really need it for your >> particular VMM, I kind of suggest not upstreaming this patch. I see it >> as a step backwards for the upstream project. >> > > If there are better ways to achieve this, we're all ears, but I think > that having a PCD which could either be fixed at build and compiled > out completely, or be set via a NULL library resolution, or even be > wired to a menu option (using PcdsDynamicHii] is a rather low-impact > but flexible way to go about this. How about using PCDs, but at a higher level in the edk2 network stack (regardless of the SNP driver(s) used)? Not that I'm a huge fan of them, but we already have PcdIPv4PXESupport and PcdIPv6PXESupport, and they can be set for OVMF and ArmVirtQemu via fw_cfg. If both PCDs are "PXE_DISABLED" (0), then PxeBcDriverEntryPoint() [NetworkPkg/UefiPxeBcDxe/PxeBcDriver.c] exits early. See: - https://bugzilla.tianocore.org/show_bug.cgi?id=1695 - https://bugzilla.tianocore.org/show_bug.cgi?id=2681 So that's at least "prior art". If similar PCDs could be introduced for other kinds of network boot (I think there's only HTTP(S)v[46] to speak of [*]), i.e. in "NetworkPkg.dec", then I guess setting those from fw_cfg in ArmVirtQemu and OVMF could be fine. I assume HttpBootDxe would be the driver to short-circuit. [*] Hmm, maybe not just that. Do we consider booting off an iSCSI device "network boot"? Perhaps where you want to "cut the stack" is Ip4Dxe/Ip6Dxe. Prior art with PXE does suggest PCDs for the higher-level network boot drivers. Laszlo ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-08-04 10:54 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2022-08-04 2:52 [PATCH v1 0/2] Add support to disable VirtIo net at runtime Yuan Yu 2022-08-04 2:52 ` [PATCH v1 1/2] OvmfPkg: Introduce NetworkCfgLib Yuan Yu 2022-08-04 2:52 ` [PATCH v1 2/2] OvmfPkg: Use PcdNetworkSupport to enable/disable VirtIo net Yuan Yu 2022-08-04 5:55 ` [PATCH v1 0/2] Add support to disable VirtIo net at runtime Laszlo Ersek 2022-08-04 9:58 ` [edk2-devel] " Ard Biesheuvel 2022-08-04 10:54 ` Laszlo Ersek
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