From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] slow_map: minor improvements to ROM BAR handling Date: Tue, 22 Dec 2009 18:05:01 +0200 Message-ID: <20091222160501.GC18676@redhat.com> References: <4B30CAF2.4040409@suse.de> <20091222151911.GC18541@redhat.com> <4B30E470.2030001@redhat.com> <4B30E4BB.8000507@suse.de> <20091222152806.GA18676@redhat.com> <4B30E783.7080903@suse.de> <4B30E82A.5030702@redhat.com> <4B30E891.9050908@suse.de> <4B30EA14.7020207@redhat.com> <4B30ED34.2000000@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , kvm@vger.kernel.org To: Alexander Graf Return-path: Received: from mx1.redhat.com ([209.132.183.28]:13396 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750801AbZLVQHt (ORCPT ); Tue, 22 Dec 2009 11:07:49 -0500 Content-Disposition: inline In-Reply-To: <4B30ED34.2000000@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Dec 22, 2009 at 05:00:52PM +0100, Alexander Graf wrote: > Avi Kivity wrote: > > On 12/22/2009 05:41 PM, Alexander Graf wrote: > >> > >>> We could certainly extend emulate.c to fetch instruction bytes from > >>> userspace. It uses ->read_std() now, so we'd need to switch to > >>> ->read_emulated() and add appropriate buffering. > >>> > >> I thought the policy on emulate.c was to not have a full instruction > >> emulator but only emulate instructions that do PT modifications or MMIO > >> access? > >> > > > > It's not a policy, just laziness. With emulate_invalid_guest_state=1 > > we need many more instructions. Of course I don't want to add > > instructions just for the sake of it, since they will be untested. > > > > I'd much prefer not to run from mmio if possible - just pointing out > > it's doable. > > Right... > > >> emulator is _really_ small. It only does a few MMU specific > >> instructions, a couple of privileged ones and MMIO accessing ones. > >> > > Btw, we're in the same situation with PowerPC here. The instruction > > > > Plus, you have a fixed length instruction length, likely more regular > > too. I imagine powerpc is load/store, so you don't have to emulate a > > zillion ALU instructions? > > Well, it's certainly doable (and easier than on x86). But I'm on the > same position as you on the x86 side. Why increase the emulator size at > least 10 times if we don't have to? > > Either way, people will report bugs when / if they actually start > executing code off MMIO. So let's not care too much about it for now. > Just make sure the read-only check is in. > > Alex So I think all we need is this on top? diff --git a/hw/device-assignment.c b/hw/device-assignment.c index 066fdb6..0c3c8f4 100644 --- a/hw/device-assignment.c +++ b/hw/device-assignment.c @@ -233,7 +233,8 @@ static void assigned_dev_iomem_map_slow(PCIDevice *pci_dev, int region_num, int m; DEBUG("slow map\n"); - m = cpu_register_io_memory(slow_bar_read, slow_bar_write, region); + m = cpu_register_io_memory(slow_bar_read, region_num == PCI_ROM_SLOT ? + NULL : slow_bar_write, region); cpu_register_physical_memory(e_phys, e_size, m); /* MSI-X MMIO page */