From 936657832f2262ad04bdf16b9229ce0b1d1c174f Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Fri, 28 Jul 2017 21:19:45 +0100 Subject: [hyperv] Do not steal ownership from the Gen 2 UEFI firmware We must not steal ownership from the Gen 2 UEFI firmware, since doing so will cause an immediate system crash (most likely in the form of a reboot). This problem was masked before commit a0f6e75 ("[hyperv] Do not fail if guest OS ID MSR is already set"), since prior to that commit we would always fail if we found any non-zero guest OS identity. We now accept a non-zero previous guest OS identity in order to allow for situations such as chainloading from iPXE to another iPXE, and as a prerequisite for commit b91cc98 ("[hyperv] Cope with Windows Server 2016 enlightenments"). A proper fix would be to reverse engineer the UEFI protocols exposed within the Hyper-V Gen 2 firmware and use these to bind to the VMBus device representing the network connection, (with the native Hyper-V driver moved to become a BIOS-only feature). As an interim solution, fail to initialise the native Hyper-V driver if we detect the guest OS identity known to be used by the Gen 2 UEFI firmware. This will cause the standard all-drivers build (ipxe.efi) to fall back to using the SNP driver. Signed-off-by: Michael Brown --- src/include/ipxe/hyperv.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/include') diff --git a/src/include/ipxe/hyperv.h b/src/include/ipxe/hyperv.h index 9194a976..9b7e54a5 100644 --- a/src/include/ipxe/hyperv.h +++ b/src/include/ipxe/hyperv.h @@ -37,6 +37,13 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); */ #define HV_GUEST_OS_ID_IPXE ( ( 1ULL << 63 ) | ( 0x18aeULL << 48 ) ) +/** Guest OS identity for Gen 2 UEFI firmware + * + * This does not conform to the documented structure for guest OS + * identities. + */ +#define HV_GUEST_OS_ID_UEFI ( 1ULL << 40 ) + /** Enable hypercall page */ #define HV_HYPERCALL_ENABLE 0x00000001UL -- cgit v1.2.3-55-g7522