On Wed, Apr 03, 2013 at 11:38:30AM +0100, Marc Zyngier wrote: > On 03/04/13 11:07, Will Deacon wrote: > > On Tue, Apr 02, 2013 at 02:25:14PM +0100, Marc Zyngier wrote: > >> Our HYP init code suffers from two major design issues: > >> - it cannot support CPU hotplug, as we tear down the idmap very early > >> - it cannot perform a TLB invalidation when switching from init to > >> runtime mappings, as pages are manipulated from PL1 exclusively > > > > [...] > > > >> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S > >> index 35a463f..b2c6967 100644 > >> --- a/arch/arm/kvm/init.S > >> +++ b/arch/arm/kvm/init.S > >> @@ -21,6 +21,7 @@ > >> #include <asm/asm-offsets.h> > >> #include <asm/kvm_asm.h> > >> #include <asm/kvm_arm.h> > >> +#include <asm/kvm_mmu.h> > >> > >> /******************************************************************** > >> * Hypervisor initialization > >> @@ -47,6 +48,9 @@ __kvm_hyp_init: > >> W(b) . > >> > >> __do_hyp_init: > >> + cmp r2, #0 @ We have a SP? > >> + bne phase2 @ Yes, second stage init > >> + > >> @ Set the HTTBR to point to the hypervisor PGD pointer passed > >> mcrr p15, 4, r0, r1, c2 > >> > >> @@ -96,14 +100,35 @@ __do_hyp_init: > >> orr r0, r0, r1 > >> isb > >> mcr p15, 4, r0, c1, c0, 0 @ HSCR > >> - isb > >> > >> - @ Set stack pointer and return to the kernel > >> + eret > >> + > >> +phase2: > >> + @ Set stack pointer > >> mov sp, r2 > >> > >> @ Set HVBAR to point to the HYP vectors > >> mcr p15, 4, r3, c12, c0, 0 @ HVBAR > >> > >> + @ Jump to the trampoline page > >> + ldr r2, =#PAGE_MASK > > > > Shifting right by PAGE_SHIFT can avoid the load. > > Not really. We're masking out the top bits of "target" and adding them > to the trampoline base address, so shifting doesn't help. > > But, as you suggested offline, BFI can come to the rescue and make that > code totally fun and unreadable. How about (untested): > > ldr r2, =#TRAMPOLINE_VA > adr r3, target > bfi r2, r3, #0, #PAGE_SHIFT > mov pc, r2 > > I really like it! :) > What kind of drugs are you on? Ok, I actually like it too. > > > >> + adr r3, target > >> + bic r3, r3, r2 > >> + ldr r2, =#TRAMPOLINE_VA > >> + add r3, r3, r2 > >> + mov pc, r3 > >> + > >> + nop > > > > <insert dead chicken and voodoo chant here> > > ... "You know I'll never sleep no more" ... > Seriously, what kind of drugs are you guys on? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
