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path: root/drivers/kvm/paging_tmpl.h
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2007-07-20KVM: MMU: Store nx bit for large page shadowsAvi Kivity
We need to distinguish between large page shadows which have the nx bit set and those which don't. The problem shows up when booting a newer smp Linux kernel, where the trampoline page (which is in real mode, which uses the same shadow pages as large pages) is using the same mapping as a kernel data page, which is mapped using nx, causing kvm to spin on that page. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Remove unused large page markerAvi Kivity
This has not been used for some time, as the same information is available in the page header. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Don't cache guest access bits in the shadow page tableAvi Kivity
This was once used to avoid accessing the guest pte when upgrading the shadow pte from read-only to read-write. But usually we need to set the guest pte dirty or accessed bits anyway, so this wasn't really exploited. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Simpify accessed/dirty/present/nx bit handlingAvi Kivity
Always set the accessed and dirty bit (since having them cleared causes a read-modify-write cycle), always set the present bit, and copy the nx bit from the guest. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Remove cr0.wp tricksAvi Kivity
No longer needed as we do everything in one place. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Make setting shadow ptes atomic on i386Avi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: Make shadow pte updates atomicAvi Kivity
With guest smp, a second vcpu might see partial updates when the first vcpu services a page fault. So delay all updates until we have figured out what the pte should look like. Note that on i386, this is still not completely atomic as a 64-bit write will be split into two on a 32-bit machine. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: Move shadow pte modifications from set_pte/set_pde to set_pde_common()Avi Kivity
We want all shadow pte modifications in one place. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Fold fix_write_pf() into set_pte_common()Avi Kivity
This prevents some work from being performed twice, and, more importantly, reduces the number of places where we modify shadow ptes. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Fold fix_read_pf() into set_pte_common()Avi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Pass the guest pde to set_pte_commonAvi Kivity
We will need the accessed bit (in addition to the dirty bit) and also write access (for setting the dirty bit) in a future patch. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Move set_pte_common() to pte width dependent codeAvi Kivity
In preparation of some modifications. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Simplify fetch() a little bitAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: Use symbolic constants instead of magic numbersEddie Dong
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: MMU: Store shadow page tables as kernel virtual addresses, not physicalAvi Kivity
Simpifies things a bit. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: Update shadow pte on write to guest pteAvi Kivity
A typical demand page/copy on write pattern is: - page fault on vaddr - kvm propagates fault to guest - guest handles fault, updates pte - kvm traps write, clears shadow pte, resumes guest - guest returns to userspace, re-faults on same vaddr - kvm installs shadow pte, resumes guest - guest continues So, three vmexits for a single guest page fault. But if instead of clearing the page table entry, we update to correspond to the value that the guest has just written, we eliminate the third vmexit. This patch does exactly that, reducing kbuild time by about 10%. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16KVM: Reduce misfirings of the fork detectorAvi Kivity
The kvm mmu tries to detects forks by looking for repeated writes to a page table. If it sees a fork, it unshadows the page table so the page table copying can proceed at native speed instead of being emulated. However, the detector also triggered on simple demand paging access patterns: a linear walk of memory would of course cause repeated writes to the same pagetable page, causing it to unshadow prematurely. Fix by resetting the fork detector if we detect a demand fault. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-05-03KVM: Per-vcpu statisticsAvi Kivity
Make the exit statistics per-vcpu instead of global. This gives a 3.5% boost when running one virtual machine per core on my two socket dual core (4 cores total) machine. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-05-03KVM: MMU: Fix hugepage pdes mapping same physical address with different accessAvi Kivity
The kvm mmu keeps a shadow page for hugepage pdes; if several such pdes map the same physical address, they share the same shadow page. This is a fairly common case (kernel mappings on i386 nonpae Linux, for example). However, if the two pdes map the same memory but with different permissions, kvm will happily use the cached shadow page. If the access through the more permissive pde will occur after the access to the strict pde, an endless pagefault loop will be generated and the guest will make no progress. Fix by making the access permissions part of the cache lookup key. The fix allows Xen pae to boot on kvm and run guest domains. Thanks to Jeremy Fitzhardinge for reporting the bug and testing the fix. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-05-03KVM: MMU: Remove unnecessary check for pdptr accessAvi Kivity
We already special case the pdptr access, so no need to check it again. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-03-04KVM: CosmeticsAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-03-04KVM: mmu: add missing dirty page tracking casesAvi Kivity
We fail to mark a page dirty in three cases: - setting the accessed bit in a pte - setting the dirty bit in a pte - emulating a write into a pagetable This fix adds the missing cases. Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-02-12[PATCH] kvm: Fix gva_to_gpa()Avi Kivity
gva_to_gpa() needs to be updated to the new walk_addr() calling convention, otherwise it may oops under some circumstances. Use the opportunity to remove all the code duplication in gva_to_gpa(), which essentially repeats the calculations in walk_addr(). Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: MMU: Report nx faults to the guestAvi Kivity
With the recent guest page fault change, we perform access checks on our own instead of relying on the cpu. This means we have to perform the nx checks as well. Software like the google toolbar on windows appears to rely on this somehow. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-26[PATCH] KVM: MMU: Perform access checks in walk_addr()Avi Kivity
Check pte permission bits in walk_addr(), instead of scattering the checks all over the code. This has the following benefits: 1. We no longer set the accessed bit for accessed which fail permission checks. 2. Setting the accessed bit is simplified. 3. Under some circumstances, we used to pretend a page fault was fixed when it would actually fail the access checks. This caused an unnecessary vmexit. 4. The error code for guest page faults is now correct. The fix helps netbsd further along booting, and allows kvm to pass the new mmu testsuite. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-23[PATCH] KVM: fix bogus pagefault on writable pagesAvi Kivity
If a page is marked as dirty in the guest pte, set_pte_common() can set the writable bit on newly-instantiated shadow pte. This optimization avoids a write fault after the initial read fault. However, if a write fault instantiates the pte, fix_write_pf() incorrectly reports the fault as a guest page fault, and the guest oopses on what appears to be a correctly-mapped page. Fix is to detect the condition and only report a guest page fault on a user access to a kernel page. With the fix, a kvm guest can survive a whole night of running the kernel hacker's screensaver (make -j9 in a loop). Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-05[PATCH] KVM: MMU: Add missing dirty bitAvi Kivity
If we emulate a write, we fail to set the dirty bit on the guest pte, leading the guest to believe the page is clean, and thus lose data. Bad. Fix by setting the guest pte dirty bit under such conditions. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: add audit code to check mappings, etc are correctAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Detect oom conditions and propagate error to userspaceAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Replace atomic allocations by preallocated objectsAvi Kivity
The mmu sometimes needs memory for reverse mapping and parent pte chains. however, we can't allocate from within the mmu because of the atomic context. So, move the allocations to a central place that can be executed before the main mmu machinery, where we can bail out on failure before any damage is done. (error handling is deffered for now, but the basic structure is there) Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Treat user-mode faults as a hint that a page is no longer ↵Avi Kivity
a page table Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: oom handlingAvi Kivity
When beginning to process a page fault, make sure we have enough shadow pages available to service the fault. If not, free some pages. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Let the walker extract the target page gfn from the pteAvi Kivity
This fixes a problem where set_pte_common() looked for shadowed pages based on the page directory gfn (a huge page) instead of the actual gfn being mapped. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Write protect guest pages when a shadow is created for themAvi Kivity
When we cache a guest page table into a shadow page table, we need to prevent further access to that page by the guest, as that would render the cache incoherent. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Shadow page table cachingAvi Kivity
Define a hashtable for caching shadow page tables. Look up the cache on context switch (cr3 change) or during page faults. The key to the cache is a combination of - the guest page table frame number - the number of paging levels in the guest * we can cache real mode, 32-bit mode, pae, and long mode page tables simultaneously. this is useful for smp bootup. - the guest page table table * some kernels use a page as both a page table and a page directory. this allows multiple shadow pages to exist for that page, one per level - the "quadrant" * 32-bit mode page tables span 4MB, whereas a shadow page table spans 2MB. similarly, a 32-bit page directory spans 4GB, while a shadow page directory spans 1GB. the quadrant allows caching up to 4 shadow page tables for one guest page in one level. - a "metaphysical" bit * for real mode, and for pse pages, there is no guest page table, so set the bit to avoid write protecting the page. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Make kvm_mmu_alloc_page() return a kvm_mmu_page pointerAvi Kivity
This allows further manipulation on the shadow page table. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Make the shadow page tables also special-case paeAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Use the guest pdptrs instead of mapping cr3 in pae modeAvi Kivity
This lets us not write protect a partial page, and is anyway what a real processor does. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Fold fetch_guest() into init_walker()Avi Kivity
It is never necessary to fetch a guest entry from an intermediate page table level (except for large pages), so avoid some confusion by always descending into the lowest possible level. Rename init_walker() to walk_addr() as it is no longer restricted to initialization. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Teach the page table walker to track guest page table gfnsAvi Kivity
Saving the table gfns removes the need to walk the guest and host page tables in lockstep. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2007-01-05[PATCH] KVM: MMU: Implement simple reverse mappingAvi Kivity
Keep in each host page frame's page->private a pointer to the shadow pte which maps it. If there are multiple shadow ptes mapping the page, set bit 0 of page->private, and use the rest as a pointer to a linked list of all such mappings. Reverse mappings are needed because we when we cache shadow page tables, we must protect the guest page tables from being modified by the guest, as that would invalidate the cached ptes. Signed-off-by: Avi Kivity <avi@qumranet.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-30[PATCH] KVM: Simplify is_long_mode()Avi Kivity
Instead of doing tricky stuff with the arch dependent virtualization registers, take a peek at the guest's efer. This simlifies some code, and fixes some confusion in the mmu branch. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-13[PATCH] KVM: MMU: Ignore pcd, pwt, and pat bits on ptesAvi Kivity
The pcd, pwt, and pat bits on page table entries affect the cpu cache. Since the cache is a host resource, the guest should not be able to control it. Moreover, the meaning of these bits changes depending on whether pat is enabled or not. So, force these bits to zero on shadow page table entries at all times. Signed-off-by: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-10[PATCH] kvm: userspace interfaceAvi Kivity
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: Yaniv Kamay <yaniv@qumranet.com> Signed-off-by: Avi Kivity <avi@qumranet.com> Cc: Simon Kagstrom <simon.kagstrom@bth.se> Cc: Bernhard Rosenkraenzer <bero@arklinux.org> Signed-off-by: Uri Lublin <uril@qumranet.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Anthony Liguori <anthony@codemonkey.ws> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>