Re: [PATCH v20 27/30] LoongArch: KVM: Implement vcpu world switch
From: zhaotianrui
Date: Tue Sep 12 2023 - 05:55:58 EST
在 2023/9/8 上午4:04, WANG Xuerui 写道:
On 8/31/23 16:30, Tianrui Zhao wrote:
Implement LoongArch vcpu world switch, including vcpu enter guest and
vcpu exit from guest, both operations need to save or restore the host
and guest registers.
Reviewed-by: Bibo Mao <maobibo@xxxxxxxxxxx>
Signed-off-by: Tianrui Zhao <zhaotianrui@xxxxxxxxxxx>
---
arch/loongarch/kernel/asm-offsets.c | 32 ++++
arch/loongarch/kvm/switch.S | 255 ++++++++++++++++++++++++++++
2 files changed, 287 insertions(+)
create mode 100644 arch/loongarch/kvm/switch.S
diff --git a/arch/loongarch/kernel/asm-offsets.c
b/arch/loongarch/kernel/asm-offsets.c
index 505e4bf596..d4bbaa74c1 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <linux/kbuild.h>
#include <linux/suspend.h>
+#include <linux/kvm_host.h>
#include <asm/cpu-info.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
@@ -285,3 +286,34 @@ void output_fgraph_ret_regs_defines(void)
BLANK();
}
#endif
+
+static void __used output_kvm_defines(void)
+{
+ COMMENT(" KVM/LOONGARCH Specific offsets. ");
"LoongArch"?
Thanks, I will fix it.
+
+ OFFSET(VCPU_FCSR0, kvm_vcpu_arch, fpu.fcsr);
+ OFFSET(VCPU_FCC, kvm_vcpu_arch, fpu.fcc);
+ BLANK();
+
+ OFFSET(KVM_VCPU_ARCH, kvm_vcpu, arch);
+ OFFSET(KVM_VCPU_KVM, kvm_vcpu, kvm);
+ OFFSET(KVM_VCPU_RUN, kvm_vcpu, run);
+ BLANK();
+
+ OFFSET(KVM_ARCH_HSP, kvm_vcpu_arch, host_sp);
+ OFFSET(KVM_ARCH_HTP, kvm_vcpu_arch, host_tp);
+ OFFSET(KVM_ARCH_HANDLE_EXIT, kvm_vcpu_arch, handle_exit);
+ OFFSET(KVM_ARCH_HPGD, kvm_vcpu_arch, host_pgd);
+ OFFSET(KVM_ARCH_GEENTRY, kvm_vcpu_arch, guest_eentry);
+ OFFSET(KVM_ARCH_GPC, kvm_vcpu_arch, pc);
+ OFFSET(KVM_ARCH_GGPR, kvm_vcpu_arch, gprs);
+ OFFSET(KVM_ARCH_HESTAT, kvm_vcpu_arch, host_estat);
+ OFFSET(KVM_ARCH_HBADV, kvm_vcpu_arch, badv);
+ OFFSET(KVM_ARCH_HBADI, kvm_vcpu_arch, badi);
+ OFFSET(KVM_ARCH_HECFG, kvm_vcpu_arch, host_ecfg);
+ OFFSET(KVM_ARCH_HEENTRY, kvm_vcpu_arch, host_eentry);
+ OFFSET(KVM_ARCH_HPERCPU, kvm_vcpu_arch, host_percpu);
+
+ OFFSET(KVM_GPGD, kvm, arch.pgd);
+ BLANK();
+}
diff --git a/arch/loongarch/kvm/switch.S b/arch/loongarch/kvm/switch.S
new file mode 100644
index 0000000000..f637fcd56c
--- /dev/null
+++ b/arch/loongarch/kvm/switch.S
@@ -0,0 +1,255 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/linkage.h>
+#include <asm/stackframe.h>
+#include <asm/asm.h>
+#include <asm/asmmacro.h>
+#include <asm/regdef.h>
+#include <asm/loongarch.h>
+
+#define PT_GPR_OFFSET(x) (PT_R0 + 8*x)
+#define GGPR_OFFSET(x) (KVM_ARCH_GGPR + 8*x)
+
+.macro kvm_save_host_gpr base
+ .irp n,1,2,3,22,23,24,25,26,27,28,29,30,31
+ st.d $r\n, \base, PT_GPR_OFFSET(\n)
+ .endr
+.endm
+
+.macro kvm_restore_host_gpr base
+ .irp n,1,2,3,22,23,24,25,26,27,28,29,30,31
+ ld.d $r\n, \base, PT_GPR_OFFSET(\n)
+ .endr
+.endm
+
+/*
+ * save and restore all gprs except base register,
+ * and default value of base register is a2.
+ */
+.macro kvm_save_guest_gprs base
+ .irp
n,1,2,3,4,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+ st.d $r\n, \base, GGPR_OFFSET(\n)
+ .endr
+.endm
+
+.macro kvm_restore_guest_gprs base
+ .irp
n,1,2,3,4,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+ ld.d $r\n, \base, GGPR_OFFSET(\n)
+ .endr
+.endm
+
+/*
+ * prepare switch to guest, save host reg and restore guest reg.
+ * a2: kvm_vcpu_arch, don't touch it until 'ertn'
+ * t0, t1: temp register
+ */
+.macro kvm_switch_to_guest
+ /* set host excfg.VS=0, all exceptions share one exception entry */
+ csrrd t0, LOONGARCH_CSR_ECFG
+ bstrins.w t0, zero, CSR_ECFG_VS_SHIFT_END, CSR_ECFG_VS_SHIFT
+ csrwr t0, LOONGARCH_CSR_ECFG
+
+ /* Load up the new EENTRY */
+ ld.d t0, a2, KVM_ARCH_GEENTRY
+ csrwr t0, LOONGARCH_CSR_EENTRY
+
+ /* Set Guest ERA */
+ ld.d t0, a2, KVM_ARCH_GPC
+ csrwr t0, LOONGARCH_CSR_ERA
+
+ /* Save host PGDL */
+ csrrd t0, LOONGARCH_CSR_PGDL
+ st.d t0, a2, KVM_ARCH_HPGD
+
+ /* Switch to kvm */
+ ld.d t1, a2, KVM_VCPU_KVM - KVM_VCPU_ARCH
+
+ /* Load guest PGDL */
+ li.w t0, KVM_GPGD
+ ldx.d t0, t1, t0
+ csrwr t0, LOONGARCH_CSR_PGDL
+
+ /* Mix GID and RID */
+ csrrd t1, LOONGARCH_CSR_GSTAT
+ bstrpick.w t1, t1, CSR_GSTAT_GID_SHIFT_END, CSR_GSTAT_GID_SHIFT
+ csrrd t0, LOONGARCH_CSR_GTLBC
+ bstrins.w t0, t1, CSR_GTLBC_TGID_SHIFT_END, CSR_GTLBC_TGID_SHIFT
+ csrwr t0, LOONGARCH_CSR_GTLBC
+
+ /*
+ * Switch to guest:
+ * GSTAT.PGM = 1, ERRCTL.ISERR = 0, TLBRPRMD.ISTLBR = 0
+ * ertn
+ */
+
+ /*
+ * Enable intr in root mode with future ertn so that host interrupt
+ * can be responsed during VM runs
+ * guest crmd comes from separate gcsr_CRMD register
+ */
+ ori t0, zero, CSR_PRMD_PIE
Use "li.w" like the place several lines before?
Thanks for the advice, and this issue has been discussed before, and the
conclusion is that it need not replace "ori" with the pseudo instruction
like "li.w", as it has the same meaning.
+ csrxchg t0, t0, LOONGARCH_CSR_PRMD
+
+ /* Set PVM bit to setup ertn to guest context */
+ ori t0, zero, CSR_GSTAT_PVM
Similarly here...
+ csrxchg t0, t0, LOONGARCH_CSR_GSTAT
+
+ /* Load Guest gprs */
+ kvm_restore_guest_gprs a2
+ /* Load KVM_ARCH register */
+ ld.d a2, a2, (KVM_ARCH_GGPR + 8 * REG_A2)
+
+ ertn
+.endm
+
+ /*
+ * exception entry for general exception from guest mode
+ * - IRQ is disabled
+ * - kernel privilege in root mode
+ * - page mode keep unchanged from previous prmd in root mode
+ * - Fixme: tlb exception cannot happen since registers
relative with TLB
+ * - is still in guest mode, such as pgd table/vmid
registers etc,
+ * - will fix with hw page walk enabled in future
+ * load kvm_vcpu from reserved CSR KVM_VCPU_KS, and save a2 to
KVM_TEMP_KS
+ */
+ .text
+ .cfi_sections .debug_frame
+SYM_CODE_START(kvm_vector_entry)
+ csrwr a2, KVM_TEMP_KS
+ csrrd a2, KVM_VCPU_KS
+ addi.d a2, a2, KVM_VCPU_ARCH
+
+ /* After save gprs, free to use any gpr */
+ kvm_save_guest_gprs a2
+ /* Save guest a2 */
+ csrrd t0, KVM_TEMP_KS
+ st.d t0, a2, (KVM_ARCH_GGPR + 8 * REG_A2)
+
+ /* a2: kvm_vcpu_arch, a1 is free to use */
+ csrrd s1, KVM_VCPU_KS
+ ld.d s0, s1, KVM_VCPU_RUN
+
+ csrrd t0, LOONGARCH_CSR_ESTAT
+ st.d t0, a2, KVM_ARCH_HESTAT
+ csrrd t0, LOONGARCH_CSR_ERA
+ st.d t0, a2, KVM_ARCH_GPC
+ csrrd t0, LOONGARCH_CSR_BADV
+ st.d t0, a2, KVM_ARCH_HBADV
+ csrrd t0, LOONGARCH_CSR_BADI
+ st.d t0, a2, KVM_ARCH_HBADI
+
+ /* Restore host excfg.VS */
+ csrrd t0, LOONGARCH_CSR_ECFG
+ ld.d t1, a2, KVM_ARCH_HECFG
+ or t0, t0, t1
+ csrwr t0, LOONGARCH_CSR_ECFG
+
+ /* Restore host eentry */
+ ld.d t0, a2, KVM_ARCH_HEENTRY
+ csrwr t0, LOONGARCH_CSR_EENTRY
+
+ /* restore host pgd table */
+ ld.d t0, a2, KVM_ARCH_HPGD
+ csrwr t0, LOONGARCH_CSR_PGDL
+
+ /*
+ * Disable PGM bit to enter root mode by default with next ertn
+ */
+ ori t0, zero, CSR_GSTAT_PVM
And here.
+ csrxchg zero, t0, LOONGARCH_CSR_GSTAT
+ /*
+ * Clear GTLBC.TGID field
+ * 0: for root tlb update in future tlb instr
+ * others: for guest tlb update like gpa to hpa in future tlb
instr
+ */
+ csrrd t0, LOONGARCH_CSR_GTLBC
+ bstrins.w t0, zero, CSR_GTLBC_TGID_SHIFT_END,
CSR_GTLBC_TGID_SHIFT
+ csrwr t0, LOONGARCH_CSR_GTLBC
+ ld.d tp, a2, KVM_ARCH_HTP
+ ld.d sp, a2, KVM_ARCH_HSP
+ /* restore per cpu register */
+ ld.d u0, a2, KVM_ARCH_HPERCPU
+ addi.d sp, sp, -PT_SIZE
+
+ /* Prepare handle exception */
+ or a0, s0, zero
+ or a1, s1, zero
Similarly "move X, Y" should be clearer here.
+ ld.d t8, a2, KVM_ARCH_HANDLE_EXIT
+ jirl ra, t8, 0
+
+ or a2, s1, zero
+ addi.d a2, a2, KVM_VCPU_ARCH
+
+ /* resume host when ret <= 0 */
+ bge zero, a0, ret_to_host
"blez a0, ret_to_host"
+
+ /*
+ * return to guest
+ * save per cpu register again, maybe switched to another cpu
+ */
+ st.d u0, a2, KVM_ARCH_HPERCPU
+
+ /* Save kvm_vcpu to kscratch */
+ csrwr s1, KVM_VCPU_KS
+ kvm_switch_to_guest
+
+ret_to_host:
+ ld.d a2, a2, KVM_ARCH_HSP
+ addi.d a2, a2, -PT_SIZE
+ kvm_restore_host_gpr a2
+ jr ra
+
+SYM_INNER_LABEL(kvm_vector_entry_end, SYM_L_LOCAL)
+SYM_CODE_END(kvm_vector_entry)
+
+/*
+ * int kvm_enter_guest(struct kvm_run *run, struct kvm_vcpu *vcpu)
+ *
+ * @register_param:
+ * a0: kvm_run* run
+ * a1: kvm_vcpu* vcpu
+ */
+SYM_FUNC_START(kvm_enter_guest)
+ /* allocate space in stack bottom */
+ addi.d a2, sp, -PT_SIZE
+ /* save host gprs */
+ kvm_save_host_gpr a2
+
+ /* save host crmd,prmd csr to stack */
+ csrrd a3, LOONGARCH_CSR_CRMD
+ st.d a3, a2, PT_CRMD
+ csrrd a3, LOONGARCH_CSR_PRMD
+ st.d a3, a2, PT_PRMD
+
+ addi.d a2, a1, KVM_VCPU_ARCH
+ st.d sp, a2, KVM_ARCH_HSP
+ st.d tp, a2, KVM_ARCH_HTP
+ /* Save per cpu register */
+ st.d u0, a2, KVM_ARCH_HPERCPU
+
+ /* Save kvm_vcpu to kscratch */
+ csrwr a1, KVM_VCPU_KS
+ kvm_switch_to_guest
+SYM_INNER_LABEL(kvm_enter_guest_end, SYM_L_LOCAL)
+SYM_FUNC_END(kvm_enter_guest)
+
+SYM_FUNC_START(kvm_save_fpu)
+ fpu_save_csr a0 t1
+ fpu_save_double a0 t1
+ fpu_save_cc a0 t1 t2
+ jr ra
+SYM_FUNC_END(kvm_save_fpu)
+
+SYM_FUNC_START(kvm_restore_fpu)
+ fpu_restore_double a0 t1
+ fpu_restore_csr a0 t1
This needs to become "fpu_restore_csr a0 t1 t2" after commit
bd3c5798484a ("LoongArch: Add Loongson Binary Translation (LBT)
extension support") which is slated for Linux 6.6 and already inside
linux-next.
I will update it.
Thanks
Tianrui Zhao
+ fpu_restore_cc a0 t1 t2
+ jr ra
+SYM_FUNC_END(kvm_restore_fpu)
+
+ .section ".rodata"
+SYM_DATA(kvm_vector_size, .quad kvm_vector_entry_end -
kvm_vector_entry)
+SYM_DATA(kvm_enter_guest_size, .quad kvm_enter_guest_end -
kvm_enter_guest)