[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 5/5] xen: tolerate ACPI NVS memory overlapping with Xen allocated memory
On 09.08.24 11:45, Jan Beulich wrote: On 07.08.2024 14:05, Jan Beulich wrote:On 07.08.2024 12:41, Juergen Gross wrote:In order to minimize required special handling for running as Xen PV dom0, the memory layout is modified to match that of the host. This requires to have only RAM at the locations where Xen allocated memory is living. Unfortunately there seem to be some machines, where ACPI NVS is located at 64 MB, resulting in a conflict with the loaded kernel or the initial page tables built by Xen. As ACPI NVS needs to be accessed by the kernel only for saving and restoring it across suspend operations, it can be relocated in the dom0's memory map by swapping it with unused RAM (this is possible via modification of the dom0 P2M map).While the kernel may not (directly) need to access it for other purposes, what about AML accessing it? As you can't advertise the movement to ACPI, and as non-RAM mappings are carried out by drivers/acpi/osl.c:acpi_map() using acpi_os_ioremap(), phys-to-machine translations won't cover for that (unless I'm overlooking something, which unfortunately seems like I might be).Thinking some more about this, the above may be pointing in the wrong direction. If from acpi_os_ioremap() downwards no address translation (PFN -> MFN) occurred, then what's coming from AML would still be handled correctly as far as page table entries go. The problem then might instead be that the mapping would appear to be covering RAM, not the ACPI NVS region (and there may be checks for that). All PTE entries written go through the P->M translation. Juergen
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |