LoongArch: KVM: Remove PGD table saving during VM context switch

Commit Message

Bibo Mao Feb. 5, 2025, 9:25 a.m. UTC

PGD table for primary mmu keeps unchanged once VM is created, it
is not necessary to save PGD table pointer during VM context switch.
And it can be acquired when VCPU is created.

Signed-off-by: Bibo Mao <[e-mail]>
---
 arch/loongarch/include/asm/kvm_host.h |  2 ++
 arch/loongarch/kernel/asm-offsets.c   |  4 +---
 arch/loongarch/kvm/switch.S           | 10 +---------
 arch/loongarch/kvm/vcpu.c             | 10 ++++++++++
 4 files changed, 14 insertions(+), 12 deletions(-)


base-commit: 5c8c229261f14159b54b9a32f12e5fa89d88b905

Patch

diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index 590982cd986e..0d7a83407d84 100644
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -180,6 +180,8 @@  struct kvm_vcpu_arch {
 	unsigned long host_sp;
 	unsigned long host_tp;
 	unsigned long host_pgd;
+	/* pgd table pointer for secondary mmu */
+	unsigned long host_second_pgd;
 
 	/* Host CSRs are used when handling exits from guest */
 	unsigned long badi;
diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 8be1c38ad8eb..8c33b9b2ee40 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -289,13 +289,13 @@  static void __used output_kvm_defines(void)
 	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_HPGD, kvm_vcpu_arch, host_pgd);
+	OFFSET(KVM_ARCH_HSECPGD, kvm_vcpu_arch, host_second_pgd);
 	OFFSET(KVM_ARCH_HANDLE_EXIT, kvm_vcpu_arch, handle_exit);
 	OFFSET(KVM_ARCH_HEENTRY, kvm_vcpu_arch, host_eentry);
 	OFFSET(KVM_ARCH_GEENTRY, kvm_vcpu_arch, guest_eentry);
@@ -306,8 +306,6 @@  static void __used output_kvm_defines(void)
 	OFFSET(KVM_ARCH_HECFG, kvm_vcpu_arch, host_ecfg);
 	OFFSET(KVM_ARCH_HESTAT, kvm_vcpu_arch, host_estat);
 	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
index 0c292f818492..1598d1f53334 100644
--- a/arch/loongarch/kvm/switch.S
+++ b/arch/loongarch/kvm/switch.S
@@ -60,16 +60,8 @@ 
 	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
+	ld.d	t0, a2, KVM_ARCH_HSECPGD
 	csrwr	t0, LOONGARCH_CSR_PGDL
 
 	/* Mix GID and RID */
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index fb72095c8077..8e822b1233ff 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -1462,6 +1462,16 @@  int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	hrtimer_init(&vcpu->arch.swtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
 	vcpu->arch.swtimer.function = kvm_swtimer_wakeup;
 
+	/* Get pgd for secondary mmu */
+	vcpu->arch.host_second_pgd = (unsigned long)vcpu->kvm->arch.pgd;
+
+	/*
+	 * Get pgd for primary mmu
+	 *
+	 * Supposing current->mm == vcpu->kvm->mm and pgd table keeps unchanged
+	 * since vmm threads are created
+	 */
+	vcpu->arch.host_pgd = (unsigned long)vcpu->kvm->mm->pgd;
 	vcpu->arch.handle_exit = kvm_handle_exit;
 	vcpu->arch.guest_eentry = (unsigned long)kvm_loongarch_ops->exc_entry;
 	vcpu->arch.csr = kzalloc(sizeof(struct loongarch_csrs), GFP_KERNEL);