From 54738c097163c3f01e67ccc85462b78d4d4f495f Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 29 Jun 2011 00:22:41 +0000 Subject: KVM: PPC: Accelerate H_PUT_TCE by implementing it in real mode This improves I/O performance for guests using the PAPR paravirtualization interface by making the H_PUT_TCE hcall faster, by implementing it in real mode. H_PUT_TCE is used for updating virtual IOMMU tables, and is used both for virtual I/O and for real I/O in the PAPR interface. Since this moves the IOMMU tables into the kernel, we define a new KVM_CREATE_SPAPR_TCE ioctl to allow qemu to create the tables. The ioctl returns a file descriptor which can be used to mmap the newly created table. The qemu driver models use them in the same way as userspace managed tables, but they can be updated directly by the guest with a real-mode H_PUT_TCE implementation, reducing the number of host/guest context switches during guest IO. There are certain circumstances where it is useful for userland qemu to write to the TCE table even if the kernel H_PUT_TCE path is used most of the time. Specifically, allowing this will avoid awkwardness when we need to reset the table. More importantly, we will in the future need to write the table in order to restore its state after a checkpoint resume or migration. Signed-off-by: David Gibson Signed-off-by: Paul Mackerras Signed-off-by: Alexander Graf --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/powerpc/kvm/book3s_hv_rmhandlers.S') diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 319ff63b1f3..e6adaadcdff 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -754,7 +754,7 @@ hcall_real_table: .long 0 /* 0x14 - H_CLEAR_REF */ .long .kvmppc_h_protect - hcall_real_table .long 0 /* 0x1c - H_GET_TCE */ - .long 0 /* 0x20 - H_SET_TCE */ + .long .kvmppc_h_put_tce - hcall_real_table .long 0 /* 0x24 - H_SET_SPRG0 */ .long .kvmppc_h_set_dabr - hcall_real_table .long 0 /* 0x2c */ -- cgit v1.2.3-18-g5258