From: Anup Patel apatel@ventanamicro.com
commit 8c3ce496bd612bd21679e445f75fcabb6be997b2 upstream.
We might have RISC-V systems (such as QEMU) where VMID is not part of the TLB entry tag so these systems will have to flush all TLB entries upon any change in hgatp.VMID.
Currently, we zero-out hgatp CSR in kvm_arch_vcpu_put() and we re-program hgatp CSR in kvm_arch_vcpu_load(). For above described systems, this will flush all TLB entries whenever VCPU exits to user-space hence reducing performance.
This patch fixes above described performance issue by not clearing hgatp CSR in kvm_arch_vcpu_put().
Fixes: 34bde9d8b9e6 ("RISC-V: KVM: Implement VCPU world-switch") Cc: stable@vger.kernel.org Signed-off-by: Anup Patel apatel@ventanamicro.com Signed-off-by: Anup Patel anup@brainfault.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/kvm/vcpu.c | 2 -- 1 file changed, 2 deletions(-)
--- a/arch/riscv/kvm/vcpu.c +++ b/arch/riscv/kvm/vcpu.c @@ -653,8 +653,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu * vcpu->arch.isa); kvm_riscv_vcpu_host_fp_restore(&vcpu->arch.host_context);
- csr_write(CSR_HGATP, 0); - csr->vsstatus = csr_read(CSR_VSSTATUS); csr->vsie = csr_read(CSR_VSIE); csr->vstvec = csr_read(CSR_VSTVEC);