LoongArch: KVM: Set reserved bits as zero in CPUCFG

Supported CPUCFG information comes from function _kvm_get_cpucfg_mask().
A bit should be zero if it is reserved by HW or if it is not supported
by KVM.

Also LoongArch software page table walk feature defined in CPUCFG2_LSPW
is supported by KVM, it should be enabled by default.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Streamline kvm_check_cpucfg() and improve comments

All the checks currently done in kvm_check_cpucfg can be realized with
early returns, so just do that to avoid extra cognitive burden related
to the return value handling.

While at it, clean up comments of _kvm_get_cpucfg_mask() and
kvm_check_cpucfg(), by removing comments that are merely restatement of
the code nearby, and paraphrasing the rest so they read more natural for
English speakers (that likely are not familiar with the actual Chinese-
influenced grammar).

No functional changes intended.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Rename _kvm_get_cpucfg() to _kvm_get_cpucfg_mask()

The function is not actually a getter of guest CPUCFG, but rather
validation of the input CPUCFG ID plus information about the supported
bit flags of that CPUCFG leaf. So rename it to avoid confusion.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Fix input validation of _kvm_get_cpucfg() & kvm_check_cpucfg()

The range check for the CPUCFG ID is wrong (should have been a ||
instead of &&) and useless in effect, so fix the obvious mistake.

Furthermore, the juggling of the temp return value is unnecessary,
because it is semantically equivalent and more readable to just
return at every switch case's end. This is done too to avoid potential
bugs in the future related to the unwanted complexity.

Also, the return value of _kvm_get_cpucfg is meant to be checked, but
this was not done, so bad CPUCFG IDs wrongly fall back to the default
case and 0 is incorrectly returned; check the return value to fix the
UAPI behavior.

While at it, also remove the redundant range check in kvm_check_cpucfg,
because out-of-range CPUCFG IDs are already rejected by the -EINVAL
as returned by _kvm_get_cpucfg().

Fixes: db1ecca22edf ("LoongArch: KVM: Add LSX (128bit SIMD) support")
Fixes: 118e10cd893d ("LoongArch: KVM: Add LASX (256bit SIMD) support")
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Add LASX (256bit SIMD) support

This patch adds LASX (256bit SIMD) support for LoongArch KVM.

There will be LASX exception in KVM when guest use the LASX instructions.
KVM will enable LASX and restore the vector registers for guest and then
return to guest to continue running.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Add LSX (128bit SIMD) support

This patch adds LSX (128bit SIMD) support for LoongArch KVM.

There will be LSX exception in KVM when guest use the LSX instructions.
KVM will enable LSX and restore the vector registers for guest and then
return to guest to continue running.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Remove kvm_acquire_timer() before entering guest

Timer emulation method in VM is switch to SW timer, there are two
places where timer emulation is needed. One is during vcpu thread
context switch, the other is halt-polling with idle instruction
emulation. SW timer switching is removed during halt-polling mode,
so it is not necessary to disable SW timer before entering to guest.

This patch removes SW timer handling before entering guest mode, and
put it in HW timer restoring flow when vcpu thread is sched-in. With
this patch, vm timer emulation is simpler, there is SW/HW timer
switch only in vcpu thread context switch scenario.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Remove SW timer switch when vcpu is halt polling

With halt-polling supported, there is checking for pending events or
interrupts when vcpu executes idle instruction. Pending interrupts
include injected SW interrupts and passthrough HW interrupts, such as
HW timer interrupts, since HW timer works still even if vcpu exists from
VM mode.

Since HW timer pending interrupt can be set directly with CSR status
register, and pending HW timer interrupt checking is used in vcpu block
checking function, it is not necessary to switch to SW timer during
halt-polling. This patch adds preemption disabling in function
kvm_cpu_has_pending_timer(), and removes SW timer switching in idle
instruction emulation function.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement misc vcpu related interfaces

1, Implement LoongArch vcpu status description such as idle exits
counter, signal exits counter, cpucfg exits counter, etc.

2, Implement some misc vcpu relaterd interfaces, such as vcpu runnable,
vcpu should kick, vcpu dump regs, etc.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement vcpu load and vcpu put operations

Implement LoongArch vcpu load and vcpu put operations, including load
csr value into hardware and save csr value into vcpu structure.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement vcpu interrupt operations

Implement vcpu interrupt operations such as vcpu set irq and vcpu
clear irq, using set_gcsr_estat() to set irq which is parsed by the
irq bitmap.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement fpu operations for vcpu

Implement LoongArch fpu related interface for vcpu, such as get fpu, set
fpu, own fpu and lose fpu, etc.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement basic vcpu ioctl interfaces

Implement basic vcpu ioctl interfaces, including:

1, vcpu KVM_ENABLE_CAP ioctl interface.

2, vcpu get registers and set registers operations, it is called when
user space use the ioctl interface to get or set regs.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: KVM: Implement basic vcpu interfaces

Implement basic vcpu interfaces, including:

1, vcpu create and destroy interface, saving info into vcpu arch
structure such as vcpu exception entrance, vcpu enter guest pointer,
etc. Init vcpu timer and set address translation mode when vcpu create.

2, vcpu run interface, handling mmio, iocsr reading fault and deliver
interrupt, lose fpu before vcpu enter guest.

3, vcpu handle exit interface, getting the exit code by ESTAT register
and using kvm exception vector to handle it.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>