Michael Brown bee67e0c14 OvmfPkg: Relax assertion that interrupts do not occur at TPL_HIGH_LEVEL ... At TPL_HIGH_LEVEL, CPU interrupts are disabled (as per the UEFI specification) and so we should never encounter a situation in which an interrupt occurs at TPL_HIGH_LEVEL. The specification also restricts usage of TPL_HIGH_LEVEL to the firmware itself. However, nothing actually prevents a UEFI application from calling gBS->RaiseTPL(TPL_HIGH_LEVEL) and then violating the invariant by enabling interrupts via the STI or equivalent instruction. Some versions of the Microsoft Windows bootloader are known to do this. NestedInterruptTplLib maintains the invariant that interrupts are disabled at TPL_HIGH_LEVEL (even when performing the dark art of deliberately manipulating the stack so that IRET will return with interrupts still disabled), but does not itself rely on external code maintaining this invariant. Relax the assertion that the interrupted TPL is below TPL_HIGH_LEVEL to an error message, to allow UEFI applications such as these versions of the Microsoft Windows bootloader to continue to function. Debugged-by: Gerd Hoffmann <kraxel@redhat.com> Debugged-by: Laszlo Ersek <lersek@redhat.com> Ref: https://bugzilla.redhat.com/show_bug.cgi?id=2189136 Signed-off-by: Michael Brown <mcb30@ipxe.org> Acked-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>		2023-05-09 22:09:50 +00:00
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Iret.c	OvmfPkg: Add library to handle TPL from within nested interrupt handlers	2022-12-23 14:44:48 +00:00
Iret.h	OvmfPkg: Add library to handle TPL from within nested interrupt handlers	2022-12-23 14:44:48 +00:00
NestedInterruptTplLib.inf	OvmfPkg: Add library to handle TPL from within nested interrupt handlers	2022-12-23 14:44:48 +00:00
Tpl.c	OvmfPkg: Relax assertion that interrupts do not occur at TPL_HIGH_LEVEL	2023-05-09 22:09:50 +00:00