On Mon, Dec 21, 2015 at 2:25 PM, Andrew Baumann <andrew.baum...@microsoft.com> wrote: >> From: qemu-devel-bounces+andrew.baumann=microsoft....@nongnu.org >> [mailto:qemu-devel- >> bounces+andrew.baumann=microsoft....@nongnu.org] On Behalf Of >> Peter Crosthwaite >> Sent: Monday, 21 December 2015 13:46 >> On Wed, Dec 16, 2015 at 11:02 AM, Andrew Baumann >> <andrew.baum...@microsoft.com> wrote: >> > The SD spec for ACMD41 says that a zero argument is an "inquiry" >> > ACMD41, which does not start initialisation and is used only for >> > retrieving the OCR. However, Tianocore EDK2 (UEFI) has a bug [1]: it >> > first sends an inquiry (zero) ACMD41. If that first request returns an >> > OCR value with the power up bit (0x80000000) set, it assumes the card >> > is ready and continues, leaving the card in the wrong state. (My >> > assumption is that this works on hardware, because no real card is >> > immediately powered up upon reset.) >> > >> > This change models a delay of 0.5ms from the first ACMD41 to the power >> > being up. However, it also immediately sets the power on upon seeing a >> > non-zero (non-enquiry) ACMD41. This speeds up UEFI boot; it should >> > also account for guests that simply delay after card reset and then >> > issue an ACMD41 that they expect will succeed. > [...] >> > @@ -449,6 +462,8 @@ static const VMStateDescription sd_vmstate = { >> > .fields = (VMStateField[]) { >> > VMSTATE_UINT32(mode, SDState), >> > VMSTATE_INT32(state, SDState), >> > + VMSTATE_UINT32(ocr, SDState), >> > + VMSTATE_TIMER_PTR(ocr_power_timer, SDState), >> >> If you change the VMSTATE layout, you need to bump the version. As >> this is very common code, it may have stricter version bump >> requirements. Last I knew however, there was a way to add new fields >> at the end of VMSD without breaking backwards compatibility. Peter or >> Juan may know more. > > I'll admit that I didn't think about these issues when adding the fields, but > after a (quick) look at vmstate_save_state() and vmstate_load_state(), they > seem to be using named fields in a json format, so I don't think the order of > fields should matter if we are adding new ones. However, if we want to be > able to migrate sd instances across across this change, then we'll need to > arrange for the OCR to appear already powered-on if we're coming from a > previous version. Does VMState have a way to do that? Essentially I just need > to specify a default value for the ocr field if coming from an old vmstate > version <= 1 that differs from the value set in sd_reset(). >
You can open code post_load logic as a callback, and I think you have access to the image version from there. Regards, Peter > Andrew
