- 03 5月, 2007 1 次提交
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由 Avi Kivity 提交于
On x86, bit operations operate on a string of bits that can reside in multiple words. For example, 'btsl %eax, (blah)' will touch the word at blah+4 if %eax is between 32 and 63. The x86 emulator compensates for that by advancing the operand address by (bit offset / BITS_PER_LONG) and truncating the bit offset to the range (0..BITS_PER_LONG-1). This has a side effect of forcing the operand size to 8 bytes on 64-bit hosts. Now, a 32-bit guest goes and fork()s a process. It write protects a stack page at 0xbffff000 using the 'btr' instruction, at offset 0xffc in the page table, with bit offset 1 (for the write permission bit). The emulator now forces the operand size to 8 bytes as previously described, and an innocent page table update turns into a cross-page-boundary write, which is assumed by the mmu code not to be a page table, so it doesn't actually clear the corresponding shadow page table entry. The guest and host permissions are out of sync and guest memory is corrupted soon afterwards, leading to guest failure. Fix by not using BITS_PER_LONG as the word size; instead use the actual operand size, so we get a 32-bit write in that case. Note we still have to teach the mmu to handle cross-page-boundary writes to guest page table; but for now this allows Damn Small Linux 0.4 (2.4.20) to boot. Signed-off-by: NAvi Kivity <avi@qumranet.com>
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- 23 1月, 2007 1 次提交
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由 Avi Kivity 提交于
The various bit string instructions (bts, btc, etc.) fail to adjust the address correctly if the bit address is beyond BITS_PER_LONG. This bug creeped in as the emulator originally relied on cr2 to contain the memory address; however we now decode it from the mod r/m bits, and must adjust the offset to account for large bit indices. The patch is rather large because it switches src and dst decoding around, so that the bit index is available when decoding the memory address. This fixes workloads like the FC5 installer. Signed-off-by: NAvi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: NAndrew Morton <akpm@osdl.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 06 1月, 2007 1 次提交
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由 Avi Kivity 提交于
cmpxchg8b uses edx:eax as the compare operand, not edi:eax. cmpxchg8b is used by 32-bit pae guests to set page table entries atomically, and this is emulated touching shadowed guest page tables. Also, implement it for 32-bit hosts. Signed-off-by: NAvi Kivity <avi@qumranet.com> Acked-by: NIngo Molnar <mingo@elte.hu> Signed-off-by: NAndrew Morton <akpm@osdl.org> Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
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- 14 12月, 2006 1 次提交
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由 Avi Kivity 提交于
As per akpm's request. Signed-off-by: NAvi Kivity <avi@qumranet.com> Signed-off-by: NAndrew Morton <akpm@osdl.org> Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
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- 11 12月, 2006 1 次提交
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由 Avi Kivity 提交于
web site: http://kvm.sourceforge.net mailing list: kvm-devel@lists.sourceforge.net (http://lists.sourceforge.net/lists/listinfo/kvm-devel) The following patchset adds a driver for Intel's hardware virtualization extensions to the x86 architecture. The driver adds a character device (/dev/kvm) that exposes the virtualization capabilities to userspace. Using this driver, a process can run a virtual machine (a "guest") in a fully virtualized PC containing its own virtual hard disks, network adapters, and display. Using this driver, one can start multiple virtual machines on a host. Each virtual machine is a process on the host; a virtual cpu is a thread in that process. kill(1), nice(1), top(1) work as expected. In effect, the driver adds a third execution mode to the existing two: we now have kernel mode, user mode, and guest mode. Guest mode has its own address space mapping guest physical memory (which is accessible to user mode by mmap()ing /dev/kvm). Guest mode has no access to any I/O devices; any such access is intercepted and directed to user mode for emulation. The driver supports i386 and x86_64 hosts and guests. All combinations are allowed except x86_64 guest on i386 host. For i386 guests and hosts, both pae and non-pae paging modes are supported. SMP hosts and UP guests are supported. At the moment only Intel hardware is supported, but AMD virtualization support is being worked on. Performance currently is non-stellar due to the naive implementation of the mmu virtualization, which throws away most of the shadow page table entries every context switch. We plan to address this in two ways: - cache shadow page tables across tlb flushes - wait until AMD and Intel release processors with nested page tables Currently a virtual desktop is responsive but consumes a lot of CPU. Under Windows I tried playing pinball and watching a few flash movies; with a recent CPU one can hardly feel the virtualization. Linux/X is slower, probably due to X being in a separate process. In addition to the driver, you need a slightly modified qemu to provide I/O device emulation and the BIOS. Caveats (akpm: might no longer be true): - The Windows install currently bluescreens due to a problem with the virtual APIC. We are working on a fix. A temporary workaround is to use an existing image or install through qemu - Windows 64-bit does not work. That's also true for qemu, so it's probably a problem with the device model. [bero@arklinux.org: build fix] [simon.kagstrom@bth.se: build fix, other fixes] [uril@qumranet.com: KVM: Expose interrupt bitmap] [akpm@osdl.org: i386 build fix] [mingo@elte.hu: i386 fixes] [rdreier@cisco.com: add log levels to all printks] [randy.dunlap@oracle.com: Fix sparse NULL and C99 struct init warnings] [anthony@codemonkey.ws: KVM: AMD SVM: 32-bit host support] Signed-off-by: NYaniv Kamay <yaniv@qumranet.com> Signed-off-by: NAvi Kivity <avi@qumranet.com> Cc: Simon Kagstrom <simon.kagstrom@bth.se> Cc: Bernhard Rosenkraenzer <bero@arklinux.org> Signed-off-by: NUri Lublin <uril@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com> Signed-off-by: NAnthony Liguori <anthony@codemonkey.ws> Signed-off-by: NAndrew Morton <akpm@osdl.org> Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
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