Re: [Qemu-devel] How to access guest memory from qemu device internal
> -Origin email- > From: Peter Maydell > Sent Time: Monday, November 24, 2014 > To: Kaiyuan > Cc: Greg Kurz , qemu-devel > Subject: Re: [Qemu-devel] How to access guest memory from qemu device internal > > On 23 November 2014 at 13:18, Kaiyuan wrote: > > Thanks for your explanation about guest physical/virtual > > address and host physical/virtual address, and I think I > > asked a wrong question. Is there a function that translates > > guest Physical address to host Virtual address so that I > > can access guest space by a host pointer? > > You can use cpu_physical_memory_map() and _unmap() > for this kind of thing. (Make sure you unmap afterwards.) > > -- PMM Thank you very much for your help!Kaiyuan Liang
Re: [Qemu-devel] How to access guest memory from qemu device internal
On 23 November 2014 at 13:18, Kaiyuan wrote: > Thanks for your explanation about guest physical/virtual > address and host physical/virtual address, and I think I > asked a wrong question. Is there a function that translates > guest Physical address to host Virtual address so that I > can access guest space by a host pointer? You can use cpu_physical_memory_map() and _unmap() for this kind of thing. (Make sure you unmap afterwards.) -- PMM
Re: [Qemu-devel] How to access guest memory from qemu device internal
> -Origin email- > From: Peter Maydell > Sent Time: Friday, November 21, 2014 > To: Kaiyuan > Cc: Greg Kurz , qemu-devel > Subject: Re: [Qemu-devel] Fw:Re:Re: How to access guest memory from qemu > device internal > > On 21 November 2014 09:17, Kaiyuan wrote: > > Thanks, Greg. It's useful to me. cpu_physical_memory_read() > > looks like a wrapper of translating guest addr to host addr > > Is there a function that translates guest address to host > > physical address? > > No, QEMU never deals with host physical addresses at all. > In general there are three address types that might be > in use: > * guest virtual address > * guest physical address > * host virtual address (only relevant if talking to RAM, > rather than an emulated device) > > For devices, the guest within the VM should deal with > converting a virtual address to a guest physical address, > and should write guest physical addresses to the device. > [If you think about real hardware, where the device is > separate from the CPU, there's no way the device can know > about guest virtual addresses, which are handled by the > CPU's built in MMU.] > > So the function Greg suggests is the one you want. > > -- PMM Thanks for your explanation about guest physical/virtual address and host physical/virtual address, and I think I asked a wrong question. Is there a function that translates guest Physical address to host Virtual address so that I can access guest space by a host pointer?
Re: [Qemu-devel] How to access guest memory from qemu device internal
On Thu, 20 Nov 2014 21:25:18 +0800 (GMT+08:00) Kaiyuan wrote: > Hello, all > > I added a custom device to qemu. This device is attached to sysbus by mmio > and has an address register in which device should access the guest memory > the register point to. > I write a bare-metal program that pass an address like 0x1234ABCD to this > address register. Inside qemu device code I added, if device reads value from > register and directly accesses this value of 0x1234ABCD, it will access host > memory 0x1234ABCD rather than guest memory 0x1234ABCD. > Does qemu provide some functions that allow device to access guest memory > address? > Have a look at *_phys* functions in the QEMU header file (cpu_physical_memory_read() for exemple). > Thanks, > Kaiyuan Liang > -- G
