Re: [libvirt] [Qemu-devel] Configuring pflash devices for OVMF firmware

-----Original Message----- From: Paolo Bonzini [mailto:pbonzini@redhat.com] Sent: Friday, February 1, 2019 7:55 To: Alexandro Sanchez Bach <alexandro(a)phi.nz>; 'Markus Armbruster' <armbru(a)redhat.com&gt; Cc: 'Peter Maydell' <peter.maydell(a)linaro.org>; 'Peter Krempa' <pkrempa(a)redhat.com>; 'Qemu-block' <qemu-block(a)nongnu.org>; 'Libvirt' <libvir-list(a)redhat.com>; 'QEMU Developers' <qemu-devel(a)nongnu.org>; 'László Érsek' <lersek(a)redhat.com>; 'Justin Terry (VM)' <juterry(a)microsoft.com>; Ning, Yu <yu.ning(a)intel.com&gt; Subject: Re: [Qemu-devel] Configuring pflash devices for OVMF firmware On 01/02/19 00:28, Alexandro Sanchez Bach wrote: > (CC'd Yu Ning @ Intel's HAXM team) > > Not sure, if I'm understanding the issue correctly, but isn't > `HAX_VM_IOCTL_SET_RAM2` with the `HAX_RAM_INFO_ROM` flag precisely > what you are looking for? > > More precisely, HAX_VM_IOCTL_SET_RAM2 maps an HVA range to a GPA > range, the HAX_RAM_INFO_ROM flag should allow only guest memory reads > to that range [1]. When the guest attempts to write, this should > trigger a VM exit that will be handled by QEMU. The missing handling is in the hypervisor: if (ret == -EACCES) { /* * For some reason, during boot-up, Chrome OS guests make hundreds of * attempts to write to GPAs close to 4GB, which are mapped into BIOS * (read-only) and thus result in EPT violations. * TODO: Handle this case properly. */ hax_warning("%s: Unexpected EPT violation cause. Skipping instruction" " (len=%u)\n", __func__, vcpu->vmx.exit_instr_length); advance_rip(vcpu); return HAX_EXIT; } > Also, this seems to be handled here: > https://github.com/qemu/qemu/blob/15bede554162dda822cd762c689edb6fa3 2b > 6e3b/target/i386/hax-mem.c#L205-L207 Right, though to be precise it should be changed to if (memory_region_is_rom(section->mr) || memory_region_is_romd(section->mr)) { flags |= HAX_RAM_INFO_ROM; } for that to work.