diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2021-05-28 12:07:22 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-06-10 15:12:11 +0300 |
| commit | f33e0702d98cc5ff21f44833525b07581862eb57 (patch) | |
| tree | dfb4b5683fa2cd5245377f7eaa95dbb65b4a2fb1 /arch/powerpc/kvm/book3s_64_entry.S | |
| parent | f36011569b90b3973f07cea00c5872c4dc0c707f (diff) | |
| download | linux-f33e0702d98cc5ff21f44833525b07581862eb57.tar.xz | |
KVM: PPC: Book3S 64: Move GUEST_MODE_SKIP test into KVM
Move the GUEST_MODE_SKIP logic into KVM code. This is quite a KVM
internal detail that has no real need to be in common handlers.
Add a comment explaining the what and why of KVM "skip" interrupts.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-3-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kvm/book3s_64_entry.S')
| -rw-r--r-- | arch/powerpc/kvm/book3s_64_entry.S | 59 |
1 files changed, 58 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_64_entry.S b/arch/powerpc/kvm/book3s_64_entry.S index 7a039ea78f15..bf927e7a06af 100644 --- a/arch/powerpc/kvm/book3s_64_entry.S +++ b/arch/powerpc/kvm/book3s_64_entry.S @@ -1,6 +1,7 @@ /* SPDX-License-Identifier: GPL-2.0-only */ #include <asm/asm-offsets.h> #include <asm/cache.h> +#include <asm/exception-64s.h> #include <asm/kvm_asm.h> #include <asm/kvm_book3s_asm.h> #include <asm/ppc_asm.h> @@ -20,9 +21,12 @@ kvmppc_interrupt: * guest R12 saved in shadow VCPU SCRATCH0 * guest R13 saved in SPRN_SCRATCH0 */ -#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE std r9,HSTATE_SCRATCH2(r13) lbz r9,HSTATE_IN_GUEST(r13) + cmpwi r9,KVM_GUEST_MODE_SKIP + beq- .Lmaybe_skip +.Lno_skip: +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE cmpwi r9,KVM_GUEST_MODE_HOST_HV beq kvmppc_bad_host_intr #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE @@ -32,5 +36,58 @@ kvmppc_interrupt: #endif b kvmppc_interrupt_hv #else + ld r9,HSTATE_SCRATCH2(r13) b kvmppc_interrupt_pr #endif + +/* + * "Skip" interrupts are part of a trick KVM uses a with hash guests to load + * the faulting instruction in guest memory from the the hypervisor without + * walking page tables. + * + * When the guest takes a fault that requires the hypervisor to load the + * instruction (e.g., MMIO emulation), KVM is running in real-mode with HV=1 + * and the guest MMU context loaded. It sets KVM_GUEST_MODE_SKIP, and sets + * MSR[DR]=1 while leaving MSR[IR]=0, so it continues to fetch HV instructions + * but loads and stores will access the guest context. This is used to load + * the faulting instruction using the faulting guest effective address. + * + * However the guest context may not be able to translate, or it may cause a + * machine check or other issue, which results in a fault in the host + * (even with KVM-HV). + * + * These faults come here because KVM_GUEST_MODE_SKIP was set, so if they + * are (or are likely) caused by that load, the instruction is skipped by + * just returning with the PC advanced +4, where it is noticed the load did + * not execute and it goes to the slow path which walks the page tables to + * read guest memory. + */ +.Lmaybe_skip: + cmpwi r12,BOOK3S_INTERRUPT_MACHINE_CHECK + beq 1f + cmpwi r12,BOOK3S_INTERRUPT_DATA_STORAGE + beq 1f + cmpwi r12,BOOK3S_INTERRUPT_DATA_SEGMENT + beq 1f +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE + /* HSRR interrupts get 2 added to interrupt number */ + cmpwi r12,BOOK3S_INTERRUPT_H_DATA_STORAGE | 0x2 + beq 2f +#endif + b .Lno_skip +1: mfspr r9,SPRN_SRR0 + addi r9,r9,4 + mtspr SPRN_SRR0,r9 + ld r12,HSTATE_SCRATCH0(r13) + ld r9,HSTATE_SCRATCH2(r13) + GET_SCRATCH0(r13) + RFI_TO_KERNEL +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE +2: mfspr r9,SPRN_HSRR0 + addi r9,r9,4 + mtspr SPRN_HSRR0,r9 + ld r12,HSTATE_SCRATCH0(r13) + ld r9,HSTATE_SCRATCH2(r13) + GET_SCRATCH0(r13) + HRFI_TO_KERNEL +#endif |