When QemuFlashWrite() is asked to write a range that includes the last byte of the LBA, then the byte that the function uses to switch the flash device back to read mode (ROMD mode in KVM speak) actually falls out of the LBA.
Normally this doesn't cause visible problems. However, if the variable store and the firmware code are backed by separate flash devices, as implemented by [Qemu-devel] [PATCH v2] hw/i386/pc_sysfw: support two flash drives http://thread.gmane.org/gmane.comp.emulators.qemu/243678 plus [edk2] [edk2 PATCH] OvmfPkg: split the variable store to a separate file http://thread.gmane.org/gmane.comp.bios.tianocore.devel/5045/focus=5046 then the READ_ARRAY_CMD not only reaches a different LBA, it reaches a different qemu device. This results in a guest reboot soon after. Fix this by ensuring that we always stay within the LBA just written when issuing READ_ARRAY_CMD. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <[email protected]> --- OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c index a3fe7d8..f9c6f5c 100644 --- a/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c +++ b/OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c @@ -208,7 +208,7 @@ QemuFlashWrite ( // Restore flash to read mode // if (*NumBytes > 0) { - *Ptr = READ_ARRAY_CMD; + *(Ptr - 1) = READ_ARRAY_CMD; } return EFI_SUCCESS; -- 1.8.3.1 ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ edk2-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/edk2-devel
