On Sun, May 20, 2012 at 04:39:01PM +0300, Avi Kivity wrote: > On 05/20/2012 03:59 PM, Gleb Natapov wrote: > > > > > > > > > > > > > > Do we actually have to patch the DSDT? Or can _S3 etc be made > > > > > > > into > > > > > > > functions instead? (and talk to the bios, or even to fwcfg > > > > > > > directly?) > > > > > > > > > > > > > We better not talk to fwcfg after OSPM is started since this is > > > > > > firmware > > > > > > confing interface. > > > > > > > > > > Why not? The OS isn't going to talk to it, so we can have a driver > > > > > in ACPI. > > > > > > > > > The OS is going to talk to it since the OS is the one who interprets > > > > AML. > > > > > > I meant, not directly. So the driver in ACPI has exclusive access. > > > > > What's the difference? > > ACPI is firmware, not OS. AML is a data provided by firmware. AML's runtime is different from firmware's.
> > > > > We may want to disable fwcfg after OS bootup at all in the feature. > > > > Who knows what kind of sensitive information we may want to pass by it > > > > in the feature? May be something TPM related? > > > > > > fwcfg is for passing information to the guest. If you want to hide > > > something from the guest, just don't put it in fwcfg. > > > > > Where to put it if we want to pass it to a firmware, but not an OS. > > That was the point of fwcfg. If you want to pass something to a guest OS > > use virtio-serial. > > See above. > > > > > And I do not see any advantage > > > > of using fwcfg from AML. > > > > > > It's an alternative to patching AML. Sure it takes some effort to write > > > the driver, but afterwards we can modify the guest behaviour more > > > easily. One possible client is -M old, so you can revert to previous > > > behaviour depending on fwcfg data. > > -M old is easy to support with the current patch. You just set new > > properties to compatibility values. The code is written with this in > > mind. And this is not an alternative to patching AML as I am trying to > > explain to you below. You can eliminate patching of s4 value, but that's > > it, you still need to patch out _S3/_S4 names. > > What about > > If (Fcfg(...)) { > Method()... > } > > ? syntax error, unexpected PARSEOP_IF > > (i.e.. define the method conditionally at runtime) > > > > > > > > > (we don't need a driver in AML to avoid patching, we can have AML talk > > > to the bios and the bios drive fwcfg; but I think we'll find uses for a > > > driver). > > I am not sure what you mean. AML can't talk to the bios. It can read > > values that bios put somewhere. > > That's what I meant - communicate through memory. > What's the benefit? The patching is still needed. You need to pass address of OperationRegion() to AML. You can do it either by patching or by creating OperationRegion() code dynamically. > > I do not see advantage of this method > > and it requires patching still. > > For the existence of the names? Yes, if we can't avoid it it's a > problem. But if we can avoid patching, we should. > If we can, we should, but we can't as far as I see. The patching was here long before this patch. > > > > > > > > > > > > > Regardless, presence of _S3 name or method is all > > > > > > that needed for OS enabling S3 option. If _S3 is defined as a > > > > > > method it > > > > > > has to return Package() otherwise iasl refuses to compile it. > > > > > > > > > > Can't we Return (Package (...) { ... }) or equivalent? > > > > > > > > > We can, how does it help? > > > > > > > > > > The contents of the package can be determined at runtime. > > > > > And? _S3 name should not exists at all in order to disable S3, not return > > something different. > > > > See above. > Does not work for me, can you send me a patch that works? -- Gleb.