On Fri, Sep 18, 2020 at 05:51:27PM +0800, Peng Liang wrote:
> On 9/18/2020 4:01 PM, Andrew Jones wrote:
> > On Thu, Sep 17, 2020 at 08:00:54PM +0800, Peng Liang wrote:
> >> In AArch64, guest will read the same values of the ID regsiters with
> >> host. Both of them read the values from arm64_ftr_regs. This patch
> >> series add support to emulate and configure ID registers so that we can
> >> control the value of ID registers that guest read.
> >>
> >> v1 -> v2:
> >> - save the ID registers in sysreg file instead of a new struct
> >> - apply a checker before setting the value to the register
> >> - add doc for new KVM_CAP_ARM_CPU_FEATURE
> >>
> >> Peng Liang (7):
> >> arm64: add a helper function to traverse arm64_ftr_regs
> >> arm64: introduce check_features
> >> kvm: arm64: save ID registers to sys_regs file
> >> kvm: arm64: introduce check_user
> >> kvm: arm64: implement check_user for ID registers
> >> kvm: arm64: make ID registers configurable
> >> kvm: arm64: add KVM_CAP_ARM_CPU_FEATURE extension
> >>
> >> Documentation/virt/kvm/api.rst | 8 +
> >> arch/arm64/include/asm/cpufeature.h | 4 +
> >> arch/arm64/include/asm/kvm_coproc.h | 2 +
> >> arch/arm64/include/asm/kvm_host.h | 3 +
> >> arch/arm64/kernel/cpufeature.c | 36 +++
> >> arch/arm64/kvm/arm.c | 3 +
> >> arch/arm64/kvm/sys_regs.c | 481 +++++++++++++++++++++++++++-
> >> arch/arm64/kvm/sys_regs.h | 6 +
> >> include/uapi/linux/kvm.h | 1 +
> >> 9 files changed, 532 insertions(+), 12 deletions(-)
> >>
> >> --
> >> 2.26.2
> >>
> >
> > Hi Peng,
> >
> > I'd much rather see a series of patches where each patch converts a single
> > ID register from using ID_SANITISED() to having its own table entry, where
> > its own set_user() and reset() functions take into account its features
> > using high level arm64_ftr* functions. Any ID registers that can still
> > share code can certainly do so with some post-conversion refactoring.
> >
> > Thanks,
> > drew
> >
> > .
> >
> Hi Andrew,
>
> Thank you for your advise. I'll rework the code to use different set_user()
> for different ID registers (maybe some general registers still use shareing
> set_user()) and check the value defined by user space in its own set_user in
> next version.
>
> But do we need to implement reset() for ID registers? I think ID registers
> are read-only in guest and guest won't and can't change their values. And
> after 03fdfb2690099 ("KVM: arm64: Don't write junk to sysregs on reset"),
> we won't write junk to sysregs on reset. So their values won't change on
> reset?
If a new reset isn't needed, then that's fine. I just want each ID
register to have its requirements considered independently, rather
than trying to apply the same functions to all of them without any
apparent consideration.
Thanks,
drew
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