[PATCH v2 15/36] KVM: arm64: Move userspace system registers into separate function
From: Marc Zyngier <hidden>
Date: 2017-12-11 10:14:23
Also in:
kvm, kvmarm
On 07/12/17 17:06, Christoffer Dall wrote:
quoted hunk ↗ jump to hunk
There's a semantic difference between the EL1 registers that control operation of a kernel running in EL1 and EL1 registers that only control userspace execution in EL0. Since we can defer saving/restoring the latter, move them into their own function. We also take this chance to rename the function saving/restoring the remaining system register to make it clear this function deals with the EL1 system registers. No functional change. Reviewed-by: Andrew Jones <redacted> Signed-off-by: Christoffer Dall <redacted> --- Notes: Changes since v1: - Added comment about sp_el0 to common save sysreg save/restore functions arch/arm64/kvm/hyp/sysreg-sr.c | 44 +++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-)diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c index 68a7d164e5e1..bbfb4d01af88 100644 --- a/arch/arm64/kvm/hyp/sysreg-sr.c +++ b/arch/arm64/kvm/hyp/sysreg-sr.c@@ -33,15 +33,24 @@ static void __hyp_text __sysreg_do_nothing(struct kvm_cpu_context *ctxt) { } */ static void __hyp_text __sysreg_save_common_state(struct kvm_cpu_context *ctxt) +{ + ctxt->sys_regs[MDSCR_EL1] = read_sysreg(mdscr_el1); + + /* + * The host arm64 Linux uses sp_el0 to point to 'current' and it must + * therefore be saved/restored on every entry/exit to/from the guest. + */ + ctxt->gp_regs.regs.sp = read_sysreg(sp_el0); +} + +static void __hyp_text __sysreg_save_user_state(struct kvm_cpu_context *ctxt) { ctxt->sys_regs[ACTLR_EL1] = read_sysreg(actlr_el1);
What is the rational for keeping ACTLR_EL1 as part of the user state?
quoted hunk ↗ jump to hunk
ctxt->sys_regs[TPIDR_EL0] = read_sysreg(tpidr_el0); ctxt->sys_regs[TPIDRRO_EL0] = read_sysreg(tpidrro_el0); - ctxt->sys_regs[MDSCR_EL1] = read_sysreg(mdscr_el1); - ctxt->gp_regs.regs.sp = read_sysreg(sp_el0); } -static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt) +static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt) { ctxt->sys_regs[MPIDR_EL1] = read_sysreg(vmpidr_el2); ctxt->sys_regs[CSSELR_EL1] = read_sysreg(csselr_el1);@@ -70,31 +79,42 @@ static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt) } static hyp_alternate_select(__sysreg_call_save_host_state, - __sysreg_save_state, __sysreg_do_nothing, + __sysreg_save_el1_state, __sysreg_do_nothing, ARM64_HAS_VIRT_HOST_EXTN); void __hyp_text __sysreg_save_host_state(struct kvm_cpu_context *ctxt) { __sysreg_call_save_host_state()(ctxt); __sysreg_save_common_state(ctxt); + __sysreg_save_user_state(ctxt); } void __hyp_text __sysreg_save_guest_state(struct kvm_cpu_context *ctxt) { - __sysreg_save_state(ctxt); + __sysreg_save_el1_state(ctxt); __sysreg_save_common_state(ctxt); + __sysreg_save_user_state(ctxt); } static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctxt) { - write_sysreg(ctxt->sys_regs[ACTLR_EL1], actlr_el1); - write_sysreg(ctxt->sys_regs[TPIDR_EL0], tpidr_el0); - write_sysreg(ctxt->sys_regs[TPIDRRO_EL0], tpidrro_el0); write_sysreg(ctxt->sys_regs[MDSCR_EL1], mdscr_el1); + + /* + * The host arm64 Linux uses sp_el0 to point to 'current' and it must + * therefore be saved/restored on every entry/exit to/from the guest. + */ write_sysreg(ctxt->gp_regs.regs.sp, sp_el0); } -static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt) +static void __hyp_text __sysreg_restore_user_state(struct kvm_cpu_context *ctxt) +{ + write_sysreg(ctxt->sys_regs[ACTLR_EL1], actlr_el1);
Same here.
quoted hunk ↗ jump to hunk
+ write_sysreg(ctxt->sys_regs[TPIDR_EL0], tpidr_el0); + write_sysreg(ctxt->sys_regs[TPIDRRO_EL0], tpidrro_el0); +} + +static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt) { write_sysreg(ctxt->sys_regs[MPIDR_EL1], vmpidr_el2); write_sysreg(ctxt->sys_regs[CSSELR_EL1], csselr_el1);@@ -123,19 +143,21 @@ static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt) } static hyp_alternate_select(__sysreg_call_restore_host_state, - __sysreg_restore_state, __sysreg_do_nothing, + __sysreg_restore_el1_state, __sysreg_do_nothing, ARM64_HAS_VIRT_HOST_EXTN); void __hyp_text __sysreg_restore_host_state(struct kvm_cpu_context *ctxt) { __sysreg_call_restore_host_state()(ctxt); __sysreg_restore_common_state(ctxt); + __sysreg_restore_user_state(ctxt); } void __hyp_text __sysreg_restore_guest_state(struct kvm_cpu_context *ctxt) { - __sysreg_restore_state(ctxt); + __sysreg_restore_el1_state(ctxt); __sysreg_restore_common_state(ctxt); + __sysreg_restore_user_state(ctxt); } static void __hyp_text __fpsimd32_save_state(struct kvm_cpu_context *ctxt)
I think we should move ACTLR_EL1 to the EL1 state, allowing it to be lazily switched. See the note in D10.2.1 that recommends a VHE enabled system to have ACTLR_EL1 as a guest-only register. Thanks, M. -- Jazz is not dead. It just smells funny...