lkml.org 
[lkml]   [2016]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v2 05/21] arm64: KVM: VHE: Turn VTCR_EL2 setup into a reusable macro
    From
    Date
    On 01/02/16 13:13, Christoffer Dall wrote:
    > On Mon, Jan 25, 2016 at 03:53:39PM +0000, Marc Zyngier wrote:
    >> On a VHE-capable system, there is no point in setting VTCR_EL2
    >> at KVM init time. We can perfectly set it up when the kernel
    >> boots, removing the need for a more complicated configuration.
    >
    > what's the complicated configuration which is avoided?

    With VHE, there is no hyp-init at all, so what we avoid is a weird init
    sequence where we have to execute part of this hyp-init, but not all of it.

    >>
    >> In order to allow this, turn VTCR_EL2 setup into a macro that
    >> we'll be able to reuse at boot time.
    >>
    >> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    >> ---
    >> arch/arm64/include/asm/kvm_mmu.h | 23 +++++++++++++++++++++++
    >> arch/arm64/kvm/hyp-init.S | 18 +-----------------
    >> 2 files changed, 24 insertions(+), 17 deletions(-)
    >>
    >> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
    >> index 7364339..d3e6d7b 100644
    >> --- a/arch/arm64/include/asm/kvm_mmu.h
    >> +++ b/arch/arm64/include/asm/kvm_mmu.h
    >> @@ -56,6 +56,29 @@
    >>
    >> #ifdef __ASSEMBLY__
    >>
    >> +#include <asm/kvm_arm.h>
    >> +
    >> +.macro setup_vtcr tmp1, tmp2
    >> + mov \tmp1, #(VTCR_EL2_FLAGS & 0xffff)
    >> + movk \tmp1, #(VTCR_EL2_FLAGS >> 16), lsl #16
    >> + /*
    >> + * Read the PARange bits from ID_AA64MMFR0_EL1 and set the PS bits in
    >> + * VTCR_EL2.
    >> + */
    >> + mrs \tmp2, id_aa64mmfr0_el1
    >> + bfi \tmp1, \tmp2, #16, #3
    >> + /*
    >> + * Read the VMIDBits bits from ID_AA64MMFR1_EL1 and set the VS bit in
    >> + * VTCR_EL2.
    >> + */
    >> + mrs \tmp2, ID_AA64MMFR1_EL1
    >> + ubfx \tmp2, \tmp2, #5, #1
    >> + lsl \tmp2, \tmp2, #VTCR_EL2_VS
    >> + orr \tmp1, \tmp1, \tmp2
    >> +
    >> + msr vtcr_el2, \tmp1
    >> + isb
    >> +.endm
    >
    > this feels like an awful lot of code in a header file.

    interrupt_head.S respectfully disagrees with you ;-).

    > Is it crazy to imagine wanting to have different T0SZ for different VMs
    > in the future? In that case, the T0SZ stuff should stay in KVM...

    That's a rather compelling argument indeed. I'll see if I can turn the
    thing around in a slightly nicer way. How about moving it out of
    hyp-init.S altogether, and into C code?

    Thanks,

    M.
    --
    Jazz is not dead. It just smells funny...

    \
     
     \ /
      Last update: 2016-02-01 15:41    [W:4.373 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site