This issue is detected by Morse (https://lore.kernel.org/linux-arm-kernel/9b0da257-785b-90ba-de3c-b9ee9ccdeeba@xxxxxxx/) during the discussion for my patch. I am not quite sure about the arm, but based on the note at the head of arm/kernel/head.S, things should go that way. If any mistake, please correct me. Thanks, Pingfan On Wed, Aug 12, 2020 at 10:05 PM Pingfan Liu <kernelfans@xxxxxxxxx> wrote: > > Both arm and arm64 kernel entry point have the following prerequisite: > MMU = off, D-cache = off, I-cache = dont care. > > HVC_SOFT_RESTART call should meet this prerequisite before jumping to the > new kernel. > > Furthermore, on arm64, el2_setup doesn't set I+C bits and keeps EL2 MMU > off, and KVM resets them when its unload. These are achieved by > HVC_RESET_VECTORS call. > > Improve the document. > > Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> > Cc: James Morse <james.morse@xxxxxxx> > Cc: Russell King <linux@xxxxxxxxxxxxxxx> > Cc: Marc Zyngier <maz@xxxxxxxxxx> > Cc: Julien Thierry <julien.thierry.kdev@xxxxxxxxx> > Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx> > Cc: linux-doc@xxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > To: kvmarm@xxxxxxxxxxxxxxxxxxxxx > --- > Documentation/virt/kvm/arm/hyp-abi.rst | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/Documentation/virt/kvm/arm/hyp-abi.rst b/Documentation/virt/kvm/arm/hyp-abi.rst > index d9eba93..a95bc30 100644 > --- a/Documentation/virt/kvm/arm/hyp-abi.rst > +++ b/Documentation/virt/kvm/arm/hyp-abi.rst > @@ -40,9 +40,9 @@ these functions (see arch/arm{,64}/include/asm/virt.h): > > * :: > > - r0/x0 = HVC_RESET_VECTORS > + x0 = HVC_RESET_VECTORS (arm64 only) > > - Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials > + Disable HYP/EL2 MMU and D-cache, and reset HVBAR/VBAR_EL2 to the initials > stubs' exception vector value. This effectively disables an existing > hypervisor. > > @@ -54,7 +54,7 @@ these functions (see arch/arm{,64}/include/asm/virt.h): > x3 = x1's value when entering the next payload (arm64) > x4 = x2's value when entering the next payload (arm64) > > - Mask all exceptions, disable the MMU, move the arguments into place > + Mask all exceptions, disable the MMU and D-cache, move the arguments into place > (arm64 only), and jump to the restart address while at HYP/EL2. This > hypercall is not expected to return to its caller. > > -- > 2.7.5 > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
