kernel/arch/mips/kvm/entry.c, branch linux-5.1.y

KVM: MIPS/Entry: Update entry code to support VZ

2017-03-28T13:53:51Z

Update MIPS KVM entry code to support VZ: - We need to set GuestCtl0.GM while in guest mode. - For cores supporting GuestID, we need to set the root GuestID to match the main GuestID while in guest mode so that the root TLB refill handler writes the correct GuestID into the TLB. - For cores without GuestID where the root ASID dealiases RVA/GPA mappings, we need to load that ASID from the gpa_mm rather than the per-VCPU guest_kernel_mm or guest_user_mm, since the root TLB maps guest physical addresses. We also need to restore the normal process ASID on exit. - The normal linux process pgd needs restoring on exit, as we can't leave the GPA mappings active for kernel code. - GuestCtl0 needs saving on exit for the GExcCode field, as it may be clobbered if a preemption occurs. We also need to move the TLB refill handler to the XTLB vector at offset 0x80 on 64-bit VZ kernels, as hardware will use Root.Status.KX to determine whether a TLB refill or XTLB Refill exception is to be taken on a root TLB miss from guest mode, and KX needs to be set for kernel code to be able to access the 64-bit segments. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS: Use CP0_BadInstr[P] for emulation

2017-02-03T15:21:07Z

When exiting from the guest, store the values of the CP0_BadInstr and CP0_BadInstrP registers if they exist, which contain the encodings of the instructions which caused the last synchronous exception. When the instruction is needed for emulation, kvm_get_badinstr() and kvm_get_badinstrp() are used instead of calling kvm_get_inst() directly, to decide whether to read the saved CP0_BadInstr/CP0_BadInstrP registers (if they exist), or read the instruction from memory (if not). The use of these registers should be more robust than using kvm_get_inst(), as it actually gives the instruction encoding seen by the hardware rather than relying on user accessors after the fact, which can be fooled by incoherent icache or a racing code modification. It will also work with VZ, where the guest virtual memory isn't directly accessible by the host with user accessors. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS: Add fast path TLB refill handler

2017-02-03T15:20:53Z

Use functions from the general MIPS TLB exception vector generation code (tlbex.c) to construct a fast path TLB refill handler similar to the general one, but cut down and capable of preserving K0 and K1. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS: Support NetLogic KScratch registers

2017-02-03T15:20:52Z

tlbex.c uses the implementation dependent $22 CP0 register group on NetLogic cores, with the help of the c0_kscratch() helper. Allow these registers to be allocated by the KVM entry code too instead of assuming KScratch registers are all $31, which will also allow pgd_reg to be handled since it is allocated that way. We also drop the masking of kscratch_mask with 0xfc, as it is redundant for the standard KScratch registers (Config4.KScrExist won't have the low 2 bits set anyway), and apparently not necessary for NetLogic. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS/T&E: Activate GVA page tables in guest context

2017-02-03T15:20:51Z

Activate the GVA page tables when in guest context. This will allow the normal Linux TLB refill handler to fill from it when guest memory is read, as well as preventing accidental reading from user memory. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS: Remove duplicated ASIDs from vcpu

2017-02-03T15:20:45Z

The kvm_vcpu_arch structure contains both mm_structs for allocating MMU contexts (primarily the ASID) but it also copies the resulting ASIDs into guest_{user,kernel}_asid[] arrays which are referenced from uasm generated code. This duplication doesn't seem to serve any purpose, and it gets in the way of generalising the ASID handling across guest kernel/user modes, so lets just extract the ASID straight out of the mm_struct on demand, and in fact there are convenient cpu_context() and cpu_asid() macros for doing so. To reduce the verbosity of this code we do also add kern_mm and user_mm local variables where the kernel and user mm_structs are used. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org

KVM: MIPS: Don't clobber CP0_Status.UX

2017-01-05T13:56:32Z

On 64-bit kernels, MIPS KVM will clear CP0_Status.UX to prevent the guest (running in user mode) from accessing the 64-bit memory segments. However the previous value of CP0_Status.UX is never restored when exiting from the guest. If the user process uses 64-bit addressing (the n64 ABI) this can result in address error exceptions from the kernel if it needs to deliver a signal before returning to user mode, as the kernel will need to write a sigframe to high user addresses on the user stack which are disallowed by CP0_Status.UX=0. This is fixed by explicitly setting SX and UX again when exiting from the guest, and explicitly clearing those bits when returning to the guest. Having the SX and UX bits set when handling guest exits (rather than only when exiting to userland) will be helpful when we support VZ, since we shouldn't need to directly read or write guest memory, so it will be valid for cache management IPIs to access host user addresses. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Cc: # 4.8.x- Signed-off-by: Radim Krčmář

MIPS: KVM: Use 64-bit CP0_EBase when appropriate

2016-08-01T16:42:24Z

Update the KVM entry point to write CP0_EBase as a 64-bit register when it is 64-bits wide, and to set the WG (write gate) bit if it exists in order to write bits 63:30 (or 31:30 on MIPS32). Prior to MIPS64r6 it was UNDEFINED to perform a 64-bit read or write of a 32-bit COP0 register. Since this is dynamically generated code, generate the right type of access depending on whether the kernel is 64-bit and cpu_has_ebase_wg. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini

MIPS: KVM: Set CP0_Status.KX on MIPS64

2016-08-01T16:42:23Z

Update the KVM entry code to set the CP0_Entry.KX bit on 64-bit kernels. This is important to allow the entry code, running in kernel mode, to access the full 64-bit address space right up to the point of entering the guest, and immediately after exiting the guest, so it can safely restore & save the guest context from 64-bit segments. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini

MIPS: KVM: Make entry code MIPS64 friendly

2016-08-01T16:42:22Z

The MIPS KVM entry code (originally kvm_locore.S, later locore.S, and now entry.c) has never quite been right when built for 64-bit, using 32-bit instructions when 64-bit instructions were needed for handling 64-bit registers and pointers. Fix several cases of this now. The changes roughly fall into the following categories. - COP0 scratch registers contain guest register values and the VCPU pointer, and are themselves full width. Similarly CP0_EPC and CP0_BadVAddr registers are full width (even though technically we don't support 64-bit guest address spaces with trap & emulate KVM). Use MFC0/MTC0 for accessing them. - Handling of stack pointers and the VCPU pointer must match the pointer size of the kernel ABI (always o32 or n64), so use ADDIU. - The CPU number in thread_info, and the guest_{user,kernel}_asid arrays in kvm_vcpu_arch are all 32 bit integers, so use lw (instead of LW) to load them. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini