[PATCH v2 06/21] arm64: KVM: VHE: Patch out use of HVC
From: Christoffer Dall <hidden>
Date: 2016-02-01 13:16:11
Also in:
kvm, kvmarm, lkml
On Mon, Jan 25, 2016 at 03:53:40PM +0000, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
With VHE, the host never issues an HVC instruction to get into the KVM code, as we can simply branch there. Use runtime code patching to simplify things a bit. Signed-off-by: Marc Zyngier <redacted> --- arch/arm64/kvm/hyp.S | 7 +++++++ arch/arm64/kvm/hyp/hyp-entry.S | 38 +++++++++++++++++++++++++++++--------- 2 files changed, 36 insertions(+), 9 deletions(-)diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S index 0ccdcbb..0689a74 100644 --- a/arch/arm64/kvm/hyp.S +++ b/arch/arm64/kvm/hyp.S@@ -17,7 +17,9 @@ #include <linux/linkage.h> +#include <asm/alternative.h> #include <asm/assembler.h> +#include <asm/cpufeature.h> /* * u64 kvm_call_hyp(void *hypfn, ...);@@ -38,6 +40,11 @@ * arch/arm64/kernel/hyp_stub.S. */ ENTRY(kvm_call_hyp) +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN hvc #0 ret +alternative_else + b __vhe_hyp_call + nop +alternative_endif ENDPROC(kvm_call_hyp)diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S index 93e8d983..9e0683f 100644 --- a/arch/arm64/kvm/hyp/hyp-entry.S +++ b/arch/arm64/kvm/hyp/hyp-entry.S@@ -38,6 +38,32 @@ ldp x0, x1, [sp], #16 .endm +.macro do_el2_call + /* + * Shuffle the parameters before calling the function + * pointed to in x0. Assumes parameters in x[1,2,3]. + */ + stp lr, xzr, [sp, #-16]!
remind me why this pair isn't just doing "str" instead of "stp" with the xzr ?
+ mov lr, x0 + mov x0, x1 + mov x1, x2 + mov x2, x3 + blr lr + ldp lr, xzr, [sp], #16 +.endm + +ENTRY(__vhe_hyp_call) + do_el2_call + /* + * We used to rely on having an exception return to get + * an implicit isb. In the E2H case, we don't have it anymore. + * rather than changing all the leaf functions, just do it here + * before returning to the rest of the kernel. + */
why is this not the case with an ISB before do_el2_call then?
quoted hunk ↗ jump to hunk
+ isb + ret +ENDPROC(__vhe_hyp_call) + el1_sync: // Guest trapped into EL2 save_x0_to_x3@@ -58,19 +84,13 @@ el1_sync: // Guest trapped into EL2 mrs x0, vbar_el2 b 2f -1: stp lr, xzr, [sp, #-16]! - +1: /* - * Compute the function address in EL2, and shuffle the parameters. + * Perform the EL2 call */ kern_hyp_va x0 - mov lr, x0 - mov x0, x1 - mov x1, x2 - mov x2, x3 - blr lr + do_el2_call - ldp lr, xzr, [sp], #16 2: eret el1_trap:-- 2.1.4