Currently we request write access to all pages that get mapped into the
guest, even if the guest is only loading from the page. This reduces
the effectiveness of KSM because it means that we unshare every page we
access. Also, we always set the changed (C) bit in the guest HPTE if
it allows writing, even for a guest load.
This fixes both these problems. We pass an 'iswrite' flag to the
mmu.xlate() functions and to kvmppc_mmu_map_page() to indicate whether
the access is a load or a store. The mmu.xlate() functions now only
set C for stores. kvmppc_gfn_to_pfn() now calls gfn_to_pfn_prot()
instead of gfn_to_pfn() so that it can indicate whether we need write
access to the page, and get back a 'writable' flag to indicate whether
the page is writable or not. If that 'writable' flag is clear, we then
make the host HPTE read-only even if the guest HPTE allowed writing.
This means that we can get a protection fault when the guest writes to a
page that it has mapped read-write but which is read-only on the host
side (perhaps due to KSM having merged the page). Thus we now call
kvmppc_handle_pagefault() for protection faults as well as HPTE not found
faults. In kvmppc_handle_pagefault(), if the access was allowed by the
guest HPTE and we thus need to install a new host HPTE, we then need to
remove the old host HPTE if there is one. This is done with a new
function, kvmppc_mmu_unmap_page(), which uses kvmppc_mmu_pte_vflush() to
find and remove the old host HPTE.
Since the memslot-related functions require the KVM SRCU read lock to
be held, this adds srcu_read_lock/unlock pairs around the calls to
kvmppc_handle_pagefault().
Finally, this changes kvmppc_mmu_book3s_32_xlate_pte() to not ignore
guest HPTEs that don't permit access, and to return -EPERM for accesses
that are not permitted by the page protections.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This makes PR KVM allocate its kvm_vcpu structs from the kvm_vcpu_cache
rather than having them embedded in the kvmppc_vcpu_book3s struct,
which is allocated with vzalloc. The reason is to reduce the
differences between PR and HV KVM in order to make is easier to have
them coexist in one kernel binary.
With this, the kvm_vcpu struct has a pointer to the kvmppc_vcpu_book3s
struct. The pointer to the kvmppc_book3s_shadow_vcpu struct has moved
from the kvmppc_vcpu_book3s struct to the kvm_vcpu struct, and is only
present for 32-bit, since it is only used for 32-bit.
Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: squash in compile fix from Aneesh]
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds a per-VM mutex to provide mutual exclusion between vcpus
for accesses to and updates of the guest hashed page table (HPT).
This also makes the code use single-byte writes to the HPT entry
when updating of the reference (R) and change (C) bits. The reason
for doing this, rather than writing back the whole HPTE, is that on
non-PAPR virtual machines, the guest OS might be writing to the HPTE
concurrently, and writing back the whole HPTE might conflict with
that. Also, real hardware does single-byte writes to update R and C.
The new mutex is taken in kvmppc_mmu_book3s_64_xlate() when reading
the HPT and updating R and/or C, and in the PAPR HPT update hcalls
(H_ENTER, H_REMOVE, etc.). Having the mutex means that we don't need
to use a hypervisor lock bit in the HPT update hcalls, and we don't
need to be careful about the order in which the bytes of the HPTE are
updated by those hcalls.
The other change here is to make emulated TLB invalidations (tlbie)
effective across all vcpus. To do this we call kvmppc_mmu_pte_vflush
for all vcpus in kvmppc_ppc_book3s_64_tlbie().
For 32-bit, this makes the setting of the accessed and dirty bits use
single-byte writes, and makes tlbie invalidate shadow HPTEs for all
vcpus.
With this, PR KVM can successfully run SMP guests.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
64-bit POWER processors have a three-bit field for page protection in
the hashed page table entry (HPTE). Currently we only interpret the two
bits that were present in older versions of the architecture. The only
defined combination that has the new bit set is 110, meaning read-only
for supervisor and no access for user mode.
This adds code to kvmppc_mmu_book3s_64_xlate() to interpret the extra
bit appropriately.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Currently, PR KVM uses 4k pages for the host-side mappings of guest
memory, regardless of the host page size. When the host page size is
64kB, we might as well use 64k host page mappings for guest mappings
of 64kB and larger pages and for guest real-mode mappings. However,
the magic page has to remain a 4k page.
To implement this, we first add another flag bit to the guest VSID
values we use, to indicate that this segment is one where host pages
should be mapped using 64k pages. For segments with this bit set
we set the bits in the shadow SLB entry to indicate a 64k base page
size. When faulting in host HPTEs for this segment, we make them
64k HPTEs instead of 4k. We record the pagesize in struct hpte_cache
for use when invalidating the HPTE.
For now we restrict the segment containing the magic page (if any) to
4k pages. It should be possible to lift this restriction in future
by ensuring that the magic 4k page is appropriately positioned within
a host 64k page.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This adds the code to interpret 64k HPTEs in the guest hashed page
table (HPT), 64k SLB entries, and to tell the guest about 64k pages
in kvm_vm_ioctl_get_smmu_info(). Guest 64k pages are still shadowed
by 4k pages.
This also adds another hash table to the four we have already in
book3s_mmu_hpte.c to allow us to find all the PTEs that we have
instantiated that match a given 64k guest page.
The tlbie instruction changed starting with POWER6 to use a bit in
the RB operand to indicate large page invalidations, and to use other
RB bits to indicate the base and actual page sizes and the segment
size. 64k pages came in slightly earlier, with POWER5++.
We use one bit in vcpu->arch.hflags to indicate that the emulated
cpu supports 64k pages, and another to indicate that it has the new
tlbie definition.
The KVM_PPC_GET_SMMU_INFO ioctl presents a bit of a problem, because
the MMU capabilities depend on which CPU model we're emulating, but it
is a VM ioctl not a VCPU ioctl and therefore doesn't get passed a VCPU
fd. In addition, commonly-used userspace (QEMU) calls it before
setting the PVR for any VCPU. Therefore, as a best effort we look at
the first vcpu in the VM and return 64k pages or not depending on its
capabilities. We also make the PVR default to the host PVR on recent
CPUs that support 1TB segments (and therefore multiple page sizes as
well) so that KVM_PPC_GET_SMMU_INFO will include 64k page and 1TB
segment support on those CPUs.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This reworks kvmppc_mmu_book3s_64_xlate() to make it check the large
page bit in the hashed page table entries (HPTEs) it looks at, and
to simplify and streamline the code. The checking of the first dword
of each HPTE is now done with a single mask and compare operation,
and all the code dealing with the matching HPTE, if we find one,
is consolidated in one place in the main line of the function flow.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
At present, if the guest creates a valid SLB (segment lookaside buffer)
entry with the slbmte instruction, then invalidates it with the slbie
instruction, then reads the entry with the slbmfee/slbmfev instructions,
the result of the slbmfee will have the valid bit set, even though the
entry is not actually considered valid by the host. This is confusing,
if not worse. This fixes it by zeroing out the orige and origv fields
of the SLB entry structure when the entry is invalidated.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
With this, the guest can use 1TB segments as well as 256MB segments.
Since we now have the situation where a single emulated guest segment
could correspond to multiple shadow segments (as the shadow segments
are still 256MB segments), this adds a new kvmppc_mmu_flush_segment()
to scan for all shadow segments that need to be removed.
This restructures the guest HPT (hashed page table) lookup code to
use the correct hashing and matching functions for HPTEs within a
1TB segment. We use the standard hpt_hash() function instead of
open-coding the hash calculation, and we use HPTE_V_COMPARE() with
an AVPN value that has the B (segment size) field included. The
calculation of avpn is done a little earlier since it doesn't change
in the loop starting at the do_second label.
The computation in kvmppc_mmu_book3s_64_esid_to_vsid() changes so that
it returns a 256MB VSID even if the guest SLB entry is a 1TB entry.
This is because the users of this function are creating 256MB SLB
entries. We set a new VSID_1T flag so that entries created from 1T
segments don't collide with entries from 256MB segments.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
The loop in kvmppc_mmu_book3s_64_xlate() that looks up a translation
in the guest hashed page table (HPT) keeps going if it finds an
HPTE that matches but doesn't allow access. This is incorrect; it
is different from what the hardware does, and there should never be
more than one matching HPTE anyway. This fixes it to stop when any
matching HPTE is found.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
When running a PAPR guest, the guest is not allowed to set SDR1 - instead
the HTAB information is held in internal hypervisor structures. But all of
our current code relies on SDR1 and walking the HTAB like on real hardware.
So in order to not be too intrusive, we simply set SDR1 to the HTAB we hold
in host memory. That way we can keep the HTAB in user space, but use it from
kernel space to map the guest.
Signed-off-by: Alexander Graf <agraf@suse.de>
This moves the slb field, which represents the state of the emulated
SLB, from the kvmppc_vcpu_book3s struct to the kvm_vcpu_arch, and the
hpte_hash_[v]pte[_long] fields from kvm_vcpu_arch to kvmppc_vcpu_book3s.
This is in accord with the principle that the kvm_vcpu_arch struct
represents the state of the emulated CPU, and the kvmppc_vcpu_book3s
struct holds the auxiliary data structures used in the emulation.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
We need to override EA as well as PA lookups for the magic page. When the guest
tells us to project it, the magic page overrides any guest mappings.
In order to reflect that, we need to hook into all the MMU layers of KVM to
force map the magic page if necessary.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
One of the most obvious registers to share with the guest directly is the
MSR. The MSR contains the "interrupts enabled" flag which the guest has to
toggle in critical sections.
So in order to bring the overhead of interrupt en- and disabling down, let's
put msr into the shared page. Keep in mind that even though you can fully read
its contents, writing to it doesn't always update all state. There are a few
safe fields that don't require hypervisor interaction. See the documentation
for a list of MSR bits that are safe to be set from inside the guest.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
Book3S_64 didn't set VSID_PR when we're in PR=1. This lead to pretty bad
behavior when searching for the shadow segment, as part of the code relied
on VSID_PR being set.
This patch fixes booting Book3S_64 guests.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
When in split mode, instruction relocation and data relocation are not equal.
So far we implemented this mode by reserving a special pseudo-VSID for the
two cases and flushing all PTEs when going into split mode, which is slow.
Unfortunately 32bit Linux and Mac OS X use split mode extensively. So to not
slow down things too much, I came up with a different idea: Mark the split
mode with a bit in the VSID and then treat it like any other segment.
This means we can just flush the shadow segment cache, but keep the PTEs
intact. I verified that this works with ppc32 Linux and Mac OS X 10.4
guests and does speed them up.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
There are some pieces in the code that I overlooked that still use
u64s instead of longs. This slows down 32 bit hosts unnecessarily, so
let's just move them to ulong.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
We already have some inline fuctions we use to access vcpu or svcpu structs,
depending on whether we're on booke or book3s. Since we just put a few more
registers into the svcpu, we also need to make sure the respective callbacks
are available and get used.
So this patch moves direct use of the now in the svcpu struct fields to
inline function calls. While at it, it also moves the definition of those
inline function calls to respective header files for booke and book3s,
greatly improving readability.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
An SLB entry contains two pieces of information related to size:
1) PTE size
2) SLB size
The L bit defines the PTE be "large" (usually means 16MB),
SLB_VSID_B_1T defines that the SLB should span 1 GB instead of the
default 256MB.
Apparently I messed things up and just put those two in one box,
shaked it heavily and came up with the current code which handles
large pages incorrectly, because it also treats large page SLB entries
as "1TB" segment entries.
This patch splits those two features apart, making Linux guests boot
even when they have > 256MB.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
We were shifting the Ks/Kp/N bits one bit too far on mtsrin. It took
me some time to figure that out, so I also put in some debugging and a
comment explaining the conversion.
This fixes current OpenBIOS boot on PPC64 KVM.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
Currently userspace has no chance to find out which virtual address space we're
in and resolve addresses. While that is a big problem for migration, it's also
unpleasent when debugging, as gdb and the monitor don't work on virtual
addresses.
This patch exports enough of the MMU segment state to userspace to make
debugging work and thus also includes the groundwork for migration.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To be able to run a guest, we also need to implement a guest MMU.
This patch adds MMU handling for Book3s_64 guests.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
