From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42020) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d5d56-0002uW-PH for qemu-devel@nongnu.org; Tue, 02 May 2017 15:03:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d5d55-0001XF-3l for qemu-devel@nongnu.org; Tue, 02 May 2017 15:03:28 -0400 Received: from mail-wm0-x242.google.com ([2a00:1450:400c:c09::242]:35650) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1d5d54-0001WL-RA for qemu-devel@nongnu.org; Tue, 02 May 2017 15:03:27 -0400 Received: by mail-wm0-x242.google.com with SMTP id d79so6954558wmi.2 for ; Tue, 02 May 2017 12:03:26 -0700 (PDT) MIME-Version: 1.0 References: <20170424130355.31324-1-marcandre.lureau@redhat.com> <20170502091723.3a3b4e42@nial.brq.redhat.com> In-Reply-To: <20170502091723.3a3b4e42@nial.brq.redhat.com> From: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= Date: Tue, 02 May 2017 19:03:15 +0000 Message-ID: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] RFC: vmcoreinfo device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: Ladi Prosek , Eduardo Habkost , "Michael S. Tsirkin" , qemu-devel , anderson@redhat.com, Paolo Bonzini , Laszlo Ersek , Richard Henderson Hi On Tue, May 2, 2017 at 11:17 AM Igor Mammedov wrote: > On Fri, 28 Apr 2017 14:28:38 +0000 > Marc-Andr=C3=A9 Lureau wrote: > > > Hi > > > > On Fri, Apr 28, 2017 at 6:12 PM Ladi Prosek wrote: > > > > > On Mon, Apr 24, 2017 at 3:03 PM, Marc-Andr=C3=A9 Lureau > > > wrote: > > > > The VM coreinfo (vmcoreinfo) device is an emulated device which > > > > exposes a 4k memory range to the guest to store various information= s > > > > useful to debug the guest OS. (it is greatly inspired by the VMGENI= D > > > > 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/vmco= reinfo > > > > > > 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. Woul= d > > > 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) > > pvpanic is x86-only afaict. While I think vmcoreinfo would work fine with any acpi-able arch. I think I would rather modify the windows driver to support both pvpanic & vmcoreinfo, even if it's not typical for driver to implement several devices. > > > > +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 =3D VMCOREIN | > > > > ++-----------------------------------+ > > > > +| ... | TOP OF PAGE > > > > +| VCIA dword object ----------------|-----> > > > +---------------------------+ > > > > +| ... | | fw-allocated array f= or > > > | > > > > +| _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 kin= d > > > 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! > > -- Marc-Andr=C3=A9 Lureau