On 03/04/2012 12:38 PM, Gleb Natapov wrote: > On Sun, Mar 04, 2012 at 12:36:20PM +0200, Avi Kivity wrote: > > On 03/04/2012 10:12 AM, Gleb Natapov wrote: > > > On Sat, Mar 03, 2012 at 10:56:02PM -0800, Jordan Justen wrote: > > > > On Tue, Oct 25, 2011 at 00:47, Avi Kivity <a...@redhat.com> wrote: > > > > > The core issue that kvm (the kernel part) supports two styles of > > > > > memory: > > > > > read/write RAM, and read/write MMIO. ROM wants writes to be ignored, > > > > > and rom/device wants reads serviced from memory and writes serviced by > > > > > userspace (as MMIO). > > > > > > > > > > It should not be too hard to patch kvm to support these additional two > > > > > styles. The entry point is the KVM_SET_USER_MEMORY_REGION ioctl to > > > > > define the new attributes for the region, and kvm_mmu_page_fault() to > > > > > map these pages as read-only and emulate writes (for ROM/device > > > > > regions). > > > > > > > > Additional context for CC'd kvm-devel: I would like to support > > > > executing from an emulated flash memory on kvm. The flash memory > > > > would be a CFI (Firmware Hub-like) device which is programmed via MMIO > > > > at the same addresses in memory where the execution would occur. > > > > > > > > What is needed is: > > > > 1. The ability to set a region to allow read/exec, > > > > but trap to qemu on writes. > > > > 2. qemu should then be able to set the region > > > > to trap on reads/exec/writes. > > > Do you want to execute code from a flash while it traps on read/exec? > > > KVM emulator can't do that. > > > > No, he wants read/exec to go to RAM, and writes to be handled as mmio. > > This should work. > > > That's mode 1 from above and will obviously work. I am asking about mode > 2 from above. >
Mode 2 is pure mmio. You're right that kvm won't run code from that. Jordan, what's the use for mode 2? Is it just used during programming? -- error compiling committee.c: too many arguments to function
