On Fri, 28 Apr 2017 14:28:38 +0000 Marc-André Lureau <marcandre.lur...@gmail.com> wrote:
> Hi > > On Fri, Apr 28, 2017 at 6:12 PM Ladi Prosek <lpro...@redhat.com> wrote: > > > On Mon, Apr 24, 2017 at 3:03 PM, Marc-André Lureau > > <marcandre.lur...@redhat.com> wrote: > > > The VM coreinfo (vmcoreinfo) device is an emulated device which > > > exposes a 4k memory range to the guest to store various informations > > > useful to debug the guest OS. (it is greatly inspired by the VMGENID > > > device implementation) > > > > > > This is an early-boot alternative to the qemu-ga VMDUMP_INFO event > > > proposed in "[PATCH 00/21] WIP: dump: add kaslr support". > > > > > > If deemed more appropriate, we can consider writing to fw_cfg directly > > > instead of guest memory, now that qemu 2.9 supports it again. > > > > > > The proof-of-concept kernel module: > > > https://github.com/elmarco/vmgenid-test/blob/master/qemuvmci-test.c > > > > Here's a proof-of-concept Windows driver: > > > > https://github.com/ladipro/kvm-guest-drivers-windows/tree/vmcoreinfo/vmcoreinfo > > > > I just wanted to be sure that it's possible to evaluate the ADDR > > method in Windows. > > > > From a practical point of view it is unfortunate that this would be a > > completely new device. For Windows guests it means another driver > > binary and all the overhead associated with deploying it on VMs. Would > > it be too crazy to add this functionality to the pvpanic device? The > > mechanics could stay the same but it would be done under the existing > > ACPI\QEMU0001 device. > > > > pvpanic is under _SB.PCI0.ISA, that could be problematic > > and _STA is a name field. > > Someone with more experience with ACPI could tell us if that make sense to > merge both and how. > > Can't you handle 2 ACPI devices in the same windows driver instead? we use QEMU0001 to reserve IO ports for pvpanic device, ASL wise there shouldn't problems with adding _ADDR method to it but then we probably should fold vmcoreinfo into pvpanic device as well (QEMU and linux driver) > > > +Storage Format: > > > +--------------- > > > + > > > +The content is expected to use little-endian format. > > > + > > > +In order to implement an OVMF "SDT Header Probe Suppressor", the > > contents of > > > +the vmcoreinfo blob has 40 bytes of padding: > > > + > > > ++-----------------------------------+ > > > +| SSDT with OEM Table ID = VMCOREIN | > > > ++-----------------------------------+ > > > +| ... | TOP OF PAGE > > > +| VCIA dword object ----------------|-----> > > +---------------------------+ > > > +| ... | | fw-allocated array for > > | > > > +| _STA method referring to VCIA | | "etc/vmcoreinfo" > > | > > > +| ... | > > +---------------------------+ > > > +| ADDR method referring to VCIA | | 0: OVMF SDT Header probe > > | > > > +| ... | | suppressor > > | > > > ++-----------------------------------+ | 40: uint32 version field > > | > > > + | 44: info contents > > | > > > + | .... > > | > > > + > > +---------------------------+ > > > + END OF PAGE > > > + > > > +Version 0 content: > > > + > > > + uint64 paddr: > > > + Physical address of the Linux vmcoreinfo ELF note. > > > > Or physical address of the Windows crash dump header :p > > > > Is there support for Windows crash dump in qemu? > > > > Do we want to have an additional discriminator field to tell what kind > > of information was written by the guest or would Windows use a > > different version? > > > > > I guess a different version would be ok. > > Thanks a lot for looking at it!
