On Mon, Jan 25, 2016 at 03:53:54PM +0000, Marc Zyngier wrote: > With ARMv8.1 VHE, the architecture is able to (almost) transparently > run the kernel at EL2, despite being written for EL1. > > This patch takes care of the "almost" part, mostly preventing the kernel > from dropping from EL2 to EL1, and setting up the HYP configuration. > > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > --- > arch/arm64/Kconfig | 13 +++++++++++++ > arch/arm64/kernel/head.S | 32 +++++++++++++++++++++++++++++++- > 2 files changed, 44 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 8cc6228..ada34df 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -750,6 +750,19 @@ config ARM64_LSE_ATOMICS > not support these instructions and requires the kernel to be > built with binutils >= 2.25. > > +config ARM64_VHE > + bool "Enable support for Virtualization Host Extension (VHE)" Extensions (plural) > + default y > + help > + Virtualization Host Extension (VHE) allows the kernel to run same > + directly at EL2 (instead of EL1) on processors that support > + it. This leads to better performance for KVM, as it reduces s/it/them/ then? > + the cost of the world switch. > + > + Selecting this option allows the VHE feature to be detected > + at runtime, and does not affect processors that do not > + implement this feature. > + > endmenu > > endmenu > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index ffe9c2b..2a7134c 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -30,6 +30,7 @@ > #include <asm/cache.h> > #include <asm/cputype.h> > #include <asm/kernel-pgtable.h> > +#include <asm/kvm_mmu.h> > #include <asm/memory.h> > #include <asm/pgtable-hwdef.h> > #include <asm/pgtable.h> > @@ -464,8 +465,25 @@ CPU_LE( bic x0, x0, #(3 << 24) ) // Clear the EE and E0E bits for EL1 > isb > ret > > +2: > +#ifdef CONFIG_ARM64_VHE > + /* > + * Check for VHE being present. For the rest of the EL2 setup, > + * x2 being non-zero indicates that we do have VHE, and that the > + * kernel is intended to run at EL2. > + */ > + mrs x2, id_aa64mmfr1_el1 > + ubfx x2, x2, #8, #4 > +#else > + mov x2, xzr > +#endif > + > /* Hyp configuration. */ > -2: mov x0, #(1 << 31) // 64-bit EL1 > + mov x0, #HCR_RW // 64-bit EL1 > + cbz x2, set_hcr > + orr x0, x0, #HCR_TGE // Enable Host Extensions > + orr x0, x0, #HCR_E2H > +set_hcr: > msr hcr_el2, x0 > > /* Generic timers. */ > @@ -507,6 +525,9 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems > > /* Coprocessor traps. */ > mov x0, #0x33ff > + cbz x2, set_cptr > + orr x0, x0, #(3 << 20) // Don't trap FP nit: If you make that define we discussed earlier you can use it here too > +set_cptr: > msr cptr_el2, x0 // Disable copro. traps to EL2 > > #ifdef CONFIG_COMPAT > @@ -521,6 +542,15 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems > /* Stage-2 translation */ > msr vttbr_el2, xzr > > + cbz x2, install_el2_stub > + > + setup_vtcr x4, x5 > + > + mov w20, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 > + isb > + ret > + > +install_el2_stub: > /* Hypervisor stub */ > adrp x0, __hyp_stub_vectors > add x0, x0, #:lo12:__hyp_stub_vectors > -- > 2.1.4 > Otherwise: Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> -- 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
