On Tue, 31 Jan 2017 16:58:22 +0200 "Michael S. Tsirkin" <m...@redhat.com> wrote:
> On Tue, Jan 31, 2017 at 03:31:46PM +0100, Phil Dennis-Jordan wrote: > > On 18 January 2017 at 18:19, Igor Mammedov <imamm...@redhat.com> wrote: > > > On Wed, 18 Jan 2017 18:30:59 +0200 > > > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > > > >> On Wed, Jan 18, 2017 at 12:45:54PM +0100, Phil Dennis-Jordan wrote: > > > [...] > > > > > >> > I suspect more might be involved in enabling ACPI 2.0, and it should > > >> > probably be an option so as to avoid regressions. I don't know what > > >> > the best approach would be for this, so comments welcome. Should > > >> > adding the reset register to the FADT also be configurable? > > >> > > >> I would say an option to make FADT use rev 3 format would be a good > > >> idea. > > >> > > >> I'd make it the default if XP survives. > > > if XP and legacy linux survive, > > > I'd skip adding option as probably there won't be any users, > > > in unlikely case such user surfaces we always can add option later > > > but we can't do it other way around (i.e. take it away). > > > > I have now finally solved the mystery of why my FADT patch has been > > going so disastrously wrong - I've now got working code, but I'd > > appreciate some guidance on the best way to structure a patch to > > minimise further back-and forth. > > + lersek > > > The culprit turned out to be OVMF, > > specifically 2 bugs/shortcomings: > > > > 1. It completely gives up on parsing Qemu's ACPI tables if more than > > one "add pointer" linker command points to the same table. In this > > case, if you add a command for both the DSDT and X_DSDT fields of the > > FADT, it aborts completely and uses fallback tables. (The following > > InstallAcpiTable call fails if called twice with the same table type.) > > https://github.com/tianocore/edk2/blob/master/OvmfPkg/AcpiPlatformDxe/QemuFwCfgAcpi.c#L518 > > > > 2. After applying all the linker commands, it goes and rewrites part > > of the FADT anyway. Specifically, it rewrites the DSDT and X_DSDT > > fields - and it always sets one of them to 0. Which one depends on > > whether the DSDT is above the 4G barrier: > > https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c#L650 > > > > Both of these are easily fixed, and I will submit a corresponding patch to > > EDK2. > > > > With that fixed, the rest of the FADT provided by Qemu is accepted by > > OVMF and the operating systems. On the Qemu side, it does mean we'll > > need to still retain the ACPI 1.0 tables for backwards compatibility. > > > > Q1: How should the option be structured and named? Should the FADT > > revision be selectable via a sub-option on -machine? Or as a > > standalone option? Something else? WinXP is main reason why we are using 1.0 revisions, but if bumping revision doesn't affect it or later versions and linux kernel (ancient/contemporary) boots fine, I wouldn't bother with yet another option. > > Q2: To avoid any more confusion, I'd appreciate > > confirmation/clarification on the X_ and non-X FADT fields in the case > > where 32-bit pointers suffice. > > > > Q2a: DSDT/X_DSDT: Both variants appear to be de-facto required. spec doesn't say that X_DSDT is optional and Windows requires it if field is present. > > > > Q2b: FIRMWARE_CTRL/X_FIRMWARE_CTRL: leave X_FIRMWARE_CTRL zero. > > > > Q2c: X_PM1a_EVT_BLK, X_PM1a_CNT_BLK, X_PM_TMR_BLK: These all state > > "This is a required field" for both variants. > > > > Q2d: GPE0_BLK/X_GPE0_BLK: Both variants state "if this register block > > is not supported, this field contains zero." - I understand this to > > mean that when the register block IS supported and 32-bit, both > > variants must be filled. > > > > In other words, only X_FIRMWARE_CTRL stays zero in Qemu's x86 case. > > > > > > I'll come up with a revised patch in the next few days. > > > > Thanks for your help and patience so far, everyone!
