Below is a proposal for a new API for PPC to allow KVM clients
to set MMU state in a vcpu.
BookE processors have one or more software managed TLBs and
currently there is no mechanism for Qemu to initialize
or access them. This is needed for normal initialization
as well as debug.
There are 4 APIs:
-KVM_PPC_SET_MMU_TYPE allows the client to negotiate the type
of MMU with KVM-- the type determines the size and format
of the data in the other APIs
-KVM_PPC_INVALIDATE_TLB invalidates all TLB entries in all
TLBs in the vcpu
-KVM_PPC_SET_TLBE sets a TLB entry-- the Power architecture
specifies the format of the MMU data passed in
-KVM_PPC_GET_TLB allows searching, reading a specific TLB entry,
or iterating over an entire TLB. Some TLBs may have an unspecified
geometry and thus the need to be able to iterate in order
to dump the TLB. The Power architecture specifies the format
of the MMU data
Feedback welcome.
Thanks,
Stuart Yoder
------------------------------------------------------------------
KVM PPC MMU API
---------------
User space can query whether the APIs to access the vcpu mmu
is available with the KVM_CHECK_EXTENSION API using
the KVM_CAP_PPC_MMU argument.
If the KVM_CAP_PPC_MMU return value is non-zero it specifies that
the following APIs are available:
KVM_PPC_SET_MMU_TYPE
KVM_PPC_INVALIDATE_TLB
KVM_PPC_SET_TLBE
KVM_PPC_GET_MMU
KVM_PPC_SET_MMU_TYPE
--------------------
Capability: KVM_CAP_PPC_SET_MMU_TYPE
Architectures: powerpc
Type: vcpu ioctl
Parameters: __u32 mmu_type (in)
Returns: 0 if specified MMU type is supported, else -1
Sets the MMU type. Valid input values are:
BOOKE_NOHV 0x1
BOOKE_HV 0x2
A return value of 0x0 indicates that KVM supports
the specified MMU type.
KVM_PPC_INVALIDATE_TLB
----------------------
Capability: KVM_CAP_PPC_MMU
Architectures: powerpc
Type: vcpu ioctl
Parameters: none
Returns: 0 on success, -1 on error
Invalidates all TLB entries in all TLBs of the vcpu.
KVM_PPC_SET_TLBE
----------------
Capability: KVM_CAP_PPC_MMU
Architectures: powerpc
Type: vcpu ioctl
Parameters:
For mmu types BOOKE_NOHV and BOOKE_HV : struct kvm_ppc_booke_mmu (in)
Returns: 0 on success, -1 on error
Sets an MMU entry in a virtual CPU.
For mmu types BOOKE_NOHV and BOOKE_HV:
To write a TLB entry, set the mas fields of kvm_ppc_booke_mmu
as per the Power architecture.
struct kvm_ppc_booke_mmu {
union {
__u64 mas0_1;
struct {
__u32 mas0;
__u32 mas1;
};
};
__u64 mas2;
union {
__u64 mas7_3
struct {
__u32 mas7;
__u32 mas3;
};
};
union {
__u64 mas5_6
struct {
__u64 mas5;
__u64 mas6;
};
}
__u32 mas8;
};
For a mmu type of BOOKE_NOHV, the mas5 and mas8 fields
in kvm_ppc_booke_mmu are present but not supported.
KVM_PPC_GET_TLB
---------------
Capability: KVM_CAP_PPC_MMU
Architectures: powerpc
Type: vcpu ioctl
Parameters: struct kvm_ppc_get_mmu (in/out)
Returns: 0 on success
-1 on error
errno = ENOENT when iterating and there are no more entries to read
Reads an MMU entry from a virtual CPU.
struct kvm_ppc_get_mmu {
/* in */
void *mmu;
__u32 flags;
/* a bitmask of flags to the API */
/* TLB_READ_FIRST 0x1 */
/* TLB_SEARCH 0x2 */
/* out */
__u32 max_entries;
};
For mmu types BOOKE_NOHV and BOOKE_HV :
The "void *mmu" field of kvm_ppc_get_mmu points to
a struct of type "struct kvm_ppc_booke_mmu".
If TLBnCFG[NENTRY] > 0 and TLBnCFG[ASSOC] > 0, the TLB has
of known number of entries and associativity. The mas0[ESEL]
and mas2[EPN] fields specify which entry to read.
If TLBnCFG[NENTRY] == 0 the number of TLB entries is
undefined and this API can be used to iterate over
the entire TLB selected with TLBSEL in mas0.
-To read a TLB entry:
set the following fields in the mmu struct (struct kvm_ppc_booke_mmu):
flags=0
mas0[TLBSEL] // select which TLB is being read
mas0[ESEL] // select which entry is being read
mas2[EPN] // effective address
On return the following fields are updated as per the Power
architecture:
mas0
mas1
mas2
mas3
mas7
-To iterate over a TLB (read all entries):
To start an interation sequence, set the following fields in
the mmu struct (struct kvm_ppc_booke_mmu)
flags=TLB_READ_FIRST
mas0[TLBSEL] // select which TLB is being read
On return the following fields are updated:
mas0 // set as per Power arch
mas1 // set as per Power arch
mas2 // set as per Power arch
mas3 // set as per Power arch
mas7 // set as per Power arch
max_entries // Contains upper limit on number of entries that may
// be returned. A value of 0xffffffff means there is
// no meaningful upper bound.
For subsequent calls to the API the following output fields must
be passed back into the API unmodified:
flags
mas0
mas2
A return value of -ENOENT indicates that there are no more
entries to be read.
-To search for TLB entry
To search for TLB entry, set the following fields in
the mmu struct (struct kvm_ppc_booke_mmu):
flags=TLB_SEARCH
mas2[EPN] // effective address to search for
mas6 // set as per the Power arch
mas5 // set as per the Power arch
On return, the following fields are updated as per the Power
architecture:
mas0
mas1
mas2
mas3
mas7
--
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