On Wed, Dec 08, 2021 at 02:00:48PM +0000, Andrew Cooper wrote: > On 03/12/2021 07:30, Juergen Gross wrote: > > The size of the video memory of PVH guests should be set to 0 in case > > no value has been specified. > > > > Doing not so will leave it to be -1, resulting in an additional 1 kB > > of RAM being advertised in the memory map (here the output of a PVH > > Mini-OS boot with 16 MB of RAM assigned): > > > > Memory map: > > 000000000000-0000010003ff: RAM > > 0000feff8000-0000feffffff: Reserved > > 0000fc008000-0000fc00803f: ACPI > > 0000fc000000-0000fc000fff: ACPI > > 0000fc001000-0000fc007fff: ACPI > > The patch itself is fine, but some further observations based on the > memory map alone. > > It is rude to provide an unsorted memory map. > > The LAPIC range is required to be reserved by the ACPI spec, missing > here. Conversely, it's unclear what the reserved region is trying to > describe.
IIRC those are the special pages used by Xen console, store, identity page tables, ioreq... > Of the 3 ACPI ranges, one is RSDP (the first 64 bytes), one is the info > block (4k), and one is the ACPI tables themselves. > > RSDP really ought to be merged into the same block as the rest of the > ACPI tables. > > The info block must not be marked ACPI reclaimable RAM, because it is > referenced by AML inside the DSDT/etc. This is a very serious issue if > the OS actually exercises its right to reclaim those regions and use > them as RAM. There's no DSDT on PVH, but I'm unsure whether it's also marked as reclaimable RAM on HVM which does have a DSDT. Last two blocks should likely be ACPI NVS I assume. Thanks, Roger.
