From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> In preparation of using x18 as a task struct pointer register when running in the kernel, stop treating it as caller save in the KVM guest entry/exit code. Currently, the code assumes there is no need to preserve it for the host, given that it would have been assumed clobbered anyway by the function call to __guest_enter(). Instead, preserve its value and restore it upon return. Link: https://patchwork.kernel.org/patch/9836891/ Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> --- arch/arm64/kvm/hyp/entry.S | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index e5cc8d66bf53..20bd9a20ea27 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -23,6 +23,7 @@ .pushsection .hyp.text, "ax" .macro save_callee_saved_regs ctxt + str x18, [\ctxt, #CPU_XREG_OFFSET(18)] stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -38,6 +39,7 @@ ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)] ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)] ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)] + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] .endm /* @@ -87,12 +89,9 @@ alternative_else_nop_endif ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] - // Restore guest regs x19-x29, lr + // Restore guest regs x18-x29, lr restore_callee_saved_regs x18 - // Restore guest reg x18 - ldr x18, [x18, #CPU_XREG_OFFSET(18)] - // Do not touch any register after this! eret sb @@ -114,7 +113,7 @@ ENTRY(__guest_exit) // Retrieve the guest regs x0-x1 from the stack ldp x2, x3, [sp], #16 // x0, x1 - // Store the guest regs x0-x1 and x4-x18 + // Store the guest regs x0-x1 and x4-x17 stp x2, x3, [x1, #CPU_XREG_OFFSET(0)] stp x4, x5, [x1, #CPU_XREG_OFFSET(4)] stp x6, x7, [x1, #CPU_XREG_OFFSET(6)] @@ -123,9 +122,8 @@ ENTRY(__guest_exit) stp x12, x13, [x1, #CPU_XREG_OFFSET(12)] stp x14, x15, [x1, #CPU_XREG_OFFSET(14)] stp x16, x17, [x1, #CPU_XREG_OFFSET(16)] - str x18, [x1, #CPU_XREG_OFFSET(18)] - // Store the guest regs x19-x29, lr + // Store the guest regs x18-x29, lr save_callee_saved_regs x1 get_host_ctxt x2, x3 -- 2.23.0.866.gb869b98d4c-goog
