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author | James Hogan <james.hogan@imgtec.com> | 2014-05-29 10:16:35 +0100 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-05-30 13:01:48 +0200 |
commit | e30492bbe95a2495930aa7db7eacde5141e45332 (patch) | |
tree | acb0c06fb12ffae1ae9f118080c44a6e84a6b3ef /arch/mips/include | |
parent | 3a0ba77408f824b1cebf5134c710a8455d7bc8f4 (diff) | |
download | op-kernel-dev-e30492bbe95a2495930aa7db7eacde5141e45332.zip op-kernel-dev-e30492bbe95a2495930aa7db7eacde5141e45332.tar.gz |
MIPS: KVM: Rewrite count/compare timer emulation
Previously the emulation of the CPU timer was just enough to get a Linux
guest running but some shortcuts were taken:
- The guest timer interrupt was hard coded to always happen every 10 ms
rather than being timed to when CP0_Count would match CP0_Compare.
- The guest's CP0_Count register was based on the host's CP0_Count
register. This isn't very portable and fails on cores without a
CP_Count register implemented such as Ingenic XBurst. It also meant
that the guest's CP0_Cause.DC bit to disable the CP0_Count register
took no effect.
- The guest's CP0_Count register was emulated by just dividing the
host's CP0_Count register by 4. This resulted in continuity problems
when used as a clock source, since when the host CP0_Count overflows
from 0x7fffffff to 0x80000000, the guest CP0_Count transitions
discontinuously from 0x1fffffff to 0xe0000000.
Therefore rewrite & fix emulation of the guest timer based on the
monotonic kernel time (i.e. ktime_get()). Internally a 32-bit count_bias
value is added to the frequency scaled nanosecond monotonic time to get
the guest's CP0_Count. The frequency of the timer is initialised to
100MHz and cannot yet be changed, but a later patch will allow the
frequency to be configured via the KVM_{GET,SET}_ONE_REG ioctl
interface.
The timer can now be stopped via the CP0_Cause.DC bit (by the guest or
via the KVM_SET_ONE_REG ioctl interface), at which point the current
CP0_Count is stored and can be read directly. When it is restarted the
bias is recalculated such that the CP0_Count value is continuous.
Due to the nature of hrtimer interrupts any read of the guest's
CP0_Count register while it is running triggers a check for whether the
hrtimer has expired, so that the guest/userland cannot observe the
CP0_Count passing CP0_Compare without queuing a timer interrupt. This is
also taken advantage of when stopping the timer to ensure that a pending
timer interrupt is queued.
This replaces the implementation of:
- Guest read of CP0_Count
- Guest write of CP0_Count
- Guest write of CP0_Compare
- Guest write of CP0_Cause
- Guest read of HWR 2 (CC) with RDHWR
- Host read of CP0_Count via KVM_GET_ONE_REG ioctl interface
- Host write of CP0_Count via KVM_SET_ONE_REG ioctl interface
- Host write of CP0_Compare via KVM_SET_ONE_REG ioctl interface
- Host write of CP0_Cause via KVM_SET_ONE_REG ioctl interface
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: Sanjay Lal <sanjayl@kymasys.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/mips/include')
-rw-r--r-- | arch/mips/include/asm/kvm_host.h | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index 79410f8..75ed94a 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -404,8 +404,15 @@ struct kvm_vcpu_arch { u32 io_gpr; /* GPR used as IO source/target */ - /* Used to calibrate the virutal count register for the guest */ - int32_t host_cp0_count; + struct hrtimer comparecount_timer; + /* Count bias from the raw time */ + uint32_t count_bias; + /* Frequency of timer in Hz */ + uint32_t count_hz; + /* Dynamic nanosecond bias (multiple of count_period) to avoid overflow */ + s64 count_dyn_bias; + /* Period of timer tick in ns */ + u64 count_period; /* Bitmask of exceptions that are pending */ unsigned long pending_exceptions; @@ -426,8 +433,6 @@ struct kvm_vcpu_arch { uint32_t guest_kernel_asid[NR_CPUS]; struct mm_struct guest_kernel_mm, guest_user_mm; - struct hrtimer comparecount_timer; - int last_sched_cpu; /* WAIT executed */ @@ -705,7 +710,13 @@ extern enum emulation_result kvm_mips_emulate_bp_exc(unsigned long cause, extern enum emulation_result kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run); -enum emulation_result kvm_mips_emulate_count(struct kvm_vcpu *vcpu); +uint32_t kvm_mips_read_count(struct kvm_vcpu *vcpu); +void kvm_mips_write_count(struct kvm_vcpu *vcpu, uint32_t count); +void kvm_mips_write_compare(struct kvm_vcpu *vcpu, uint32_t compare); +void kvm_mips_init_count(struct kvm_vcpu *vcpu); +void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu); +void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu); +enum hrtimer_restart kvm_mips_count_timeout(struct kvm_vcpu *vcpu); enum emulation_result kvm_mips_check_privilege(unsigned long cause, uint32_t *opc, |