[PATCH 21/37] KVM: arm64: Don't save the host ELR_EL2 and SPSR_EL2 on VHE systems
From: Christoffer Dall <hidden>
Date: 2017-12-03 19:45:50
Also in:
kvm, kvmarm
On Wed, Nov 08, 2017 at 06:03:23PM +0100, Andrew Jones wrote:
On Thu, Oct 12, 2017 at 12:41:25PM +0200, Christoffer Dall wrote:quoted
On non-VHE systems we need to save the ELR_EL2 and SPSR_EL2 so that we can return to the host in EL1 in the same state and location where we issued a hypercall to EL2, but these registers don't contain anything important on VHE, because all of the host runs in EL2. Therefore, exclude them when saving/restoring the host state.This commit message implies we start excluding now, but this patch actually has no functional change. It just prepares things for patch 27/37 "KVM: arm64: Defer saving/restoring system registers to vcpu load/put on VHE". Can you please clarify it?
Sure: On non-VHE systems we need to save the ELR_EL2 and SPSR_EL2 so that we can return to the host in EL1 in the same state and location where we issued a hypercall to EL2, but these registers don't contain anything important on VHE, because all of the host runs in EL2. Therefore, factor out these registers into separate save/restore functions, making it easy to exclude them from the VHE world-switch path later on. Thanks, -Christoffer
quoted
Signed-off-by: Christoffer Dall <redacted> --- arch/arm64/kvm/hyp/sysreg-sr.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c index f5c1b44..354ca02 100644 --- a/arch/arm64/kvm/hyp/sysreg-sr.c +++ b/arch/arm64/kvm/hyp/sysreg-sr.c@@ -66,6 +66,10 @@ static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt) ctxt->gp_regs.sp_el1 = read_sysreg(sp_el1); ctxt->gp_regs.elr_el1 = read_sysreg_el1(elr); ctxt->gp_regs.spsr[KVM_SPSR_EL1]= read_sysreg_el1(spsr); +} + +static void __hyp_text __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt) +{ ctxt->gp_regs.regs.pc = read_sysreg_el2(elr); ctxt->gp_regs.regs.pstate = read_sysreg_el2(spsr); }@@ -75,6 +79,7 @@ void __hyp_text __sysreg_save_state_nvhe(struct kvm_cpu_context *ctxt) __sysreg_save_el1_state(ctxt); __sysreg_save_common_state(ctxt); __sysreg_save_user_state(ctxt); + __sysreg_save_el2_return_state(ctxt); } void sysreg_save_host_state_vhe(struct kvm_cpu_context *ctxt)@@ -88,6 +93,7 @@ void sysreg_save_guest_state_vhe(struct kvm_cpu_context *ctxt) __sysreg_save_el1_state(ctxt); __sysreg_save_common_state(ctxt); __sysreg_save_user_state(ctxt); + __sysreg_save_el2_return_state(ctxt); } static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctxt)@@ -127,6 +133,11 @@ static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt) write_sysreg(ctxt->gp_regs.sp_el1, sp_el1); write_sysreg_el1(ctxt->gp_regs.elr_el1, elr); write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr); +} + +static void __hyp_text +__sysreg_restore_el2_return_state(struct kvm_cpu_context *ctxt) +{ write_sysreg_el2(ctxt->gp_regs.regs.pc, elr); write_sysreg_el2(ctxt->gp_regs.regs.pstate, spsr); }@@ -136,6 +147,7 @@ void __hyp_text __sysreg_restore_state_nvhe(struct kvm_cpu_context *ctxt) __sysreg_restore_el1_state(ctxt); __sysreg_restore_common_state(ctxt); __sysreg_restore_user_state(ctxt); + __sysreg_restore_el2_return_state(ctxt); } void sysreg_restore_host_state_vhe(struct kvm_cpu_context *ctxt)@@ -149,6 +161,7 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt) __sysreg_restore_el1_state(ctxt); __sysreg_restore_common_state(ctxt); __sysreg_restore_user_state(ctxt); + __sysreg_restore_el2_return_state(ctxt); } static void __hyp_text __fpsimd32_save_state(struct kvm_cpu_context *ctxt)-- 2.9.0