When the guest accesses I/O memory this will create data abort
exceptions and they are handled by decoding the HSR information
(physical address, read/write, length, register) and forwarding reads
and writes to QEMU which performs the device emulation.
This requires changing the general flow somewhat since new calls to run
the VCPU must check if there's a pending MMIO load and perform the write
after QEMU has made the data available.
---
arch/arm/include/asm/kvm_host.h | 1
arch/arm/include/asm/kvm_mmu.h | 1
arch/arm/kvm/arm.c | 11 ++++
arch/arm/kvm/arm_mmu.c | 106 ++++++++++++++++++++++++++++++++++++++-
4 files changed, 115 insertions(+), 4 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 7f96974..5393e25 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -86,6 +86,7 @@ struct kvm_vcpu_arch {
u32 hpfar; /* Hyp IPA Fault Address Register */
/* IO related fields */
+ bool mmio_sign_extend; /* for byte/halfword loads */
u32 mmio_rd;
/* Misc. fields */
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index a64ab2d..f06f42d 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -40,6 +40,7 @@ void free_hyp_pmds(pgd_t *hyp_pgd);
int kvm_alloc_stage2_pgd(struct kvm *kvm);
void kvm_free_stage2_pgd(struct kvm *kvm);
+int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
#endif /* __ARM_KVM_MMU_H__ */
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index abed683..d01f234 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -349,6 +349,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct
kvm_run *run)
int ret;
for (;;) {
+ if (run->exit_reason == KVM_EXIT_MMIO) {
+ ret = kvm_handle_mmio_return(vcpu, vcpu->run);
+ if (ret)
+ break;
+ }
+
local_irq_save(flags);
ret = __kvm_vcpu_run(vcpu);
local_irq_restore(flags);
@@ -367,8 +373,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct
kvm_run *run)
kvm_err(ret, "Error in handle_exit");
break;
}
+
+ if (run->exit_reason == KVM_EXIT_MMIO)
+ break;
}
+ if (ret < 0)
+ run->exit_reason = KVM_EXIT_EXCEPTION;
return ret;
}
diff --git a/arch/arm/kvm/arm_mmu.c b/arch/arm/kvm/arm_mmu.c
index fe27e59..b04a211 100644
--- a/arch/arm/kvm/arm_mmu.c
+++ b/arch/arm/kvm/arm_mmu.c
@@ -16,9 +16,10 @@
#include <linux/mman.h>
#include <linux/kvm_host.h>
+#include <asm/pgalloc.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_mmu.h>
-#include <asm/pgalloc.h>
+#include <asm/kvm_emulate.h>
#include "../mm/mm.h"
#include "trace.h"
@@ -297,6 +298,105 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
phys_addr_t fault_ipa,
return 0;
}
+/**
+ * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
+ * @vcpu: The VCPU pointer
+ * @run: The VCPU run struct containing the mmio data
+ *
+ * This should only be called after returning to QEMU for MMIO load emulation.
+ */
+int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ int *dest;
+ unsigned int len;
+ int mask;
+
+ if (!run->mmio.is_write) {
+ dest = &vcpu_reg(vcpu, vcpu->arch.mmio_rd);
+ memset(dest, 0, sizeof(int));
+
+ if (run->mmio.len > 4) {
+ kvm_err(-EINVAL, "Incorrect mmio length");
+ return -EINVAL;
+ }
+
+ len = run->mmio.len;
+ memcpy(dest, run->mmio.data, len);
+
+ if (vcpu->arch.mmio_sign_extend && len < 4) {
+ mask = 1U << ((len * 8) - 1);
+ *dest = (*dest ^ mask) - mask;
+ }
+ }
+
+ return 0;
+}
+
+static int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
+ phys_addr_t fault_ipa, struct kvm_memory_slot *memslot)
+{
+ unsigned long rd, len, instr_len;
+ bool is_write, sign_extend;
+
+ if (!((vcpu->arch.hsr >> 24) & 1) || ((vcpu->arch.hsr >> 8) & 1)) {
+ kvm_err(-EFAULT, "Invalid I/O abort");
+ return -EFAULT;
+ }
+
+ if ((vcpu->arch.hsr >> 7) & 1) {
+ kvm_err(-EFAULT, "Translation table accesses I/O memory");
+ return -EFAULT;
+ }
+
+ switch ((vcpu->arch.hsr >> 22) & 0x3) {
+ case 0: len = 1; break;
+ case 1: len = 2; break;
+ case 2: len = 4; break;
+ default:
+ kvm_err(-EFAULT, "Invalid I/O abort");
+ return -EFAULT;
+ }
+
+ is_write = ((vcpu->arch.hsr >> 6) & 1);
+ sign_extend = ((vcpu->arch.hsr >> 21) & 1);
+ rd = (vcpu->arch.hsr >> 16) & 0xf;
+ BUG_ON(rd > 15);
+
+ if (rd == 15) {
+ kvm_err(-EFAULT, "I/O memory trying to read/write pc");
+ return -EFAULT;
+ }
+
+ /* Get instruction length in bytes */
+ instr_len = ((vcpu->arch.hsr >> 25) & 1) ? 4 : 2;
+
+ if (!memslot) {
+ /* QEMU hack for missing devices - simply return 0 */
+ if (!is_write)
+ vcpu_reg(vcpu, rd) = 0;
+ vcpu_reg(vcpu, 15) += instr_len;
+ return 0;
+ }
+
+ /* Export MMIO operations to user space */
+ vcpu->run->exit_reason = KVM_EXIT_MMIO;
+ vcpu->run->mmio.is_write = is_write;
+ vcpu->run->mmio.phys_addr = fault_ipa;
+ vcpu->run->mmio.len = len;
+ vcpu->arch.mmio_sign_extend = sign_extend;
+ vcpu->arch.mmio_rd = rd;
+
+ if (is_write)
+ memcpy(run->mmio.data, &vcpu_reg(vcpu, rd), len);
+
+ /*
+ * The MMIO instruction is emulated and should not be re-executed
+ * in the guest.
+ */
+ vcpu_reg(vcpu, 15) += instr_len;
+ return 0;
+}
+
#define HSR_ABT_FS (0x3f)
#define HPFAR_MASK (~0xf)
int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
@@ -335,7 +435,5 @@ io_mem_abort:
return -EFAULT;
}
- kvm_msg("I/O address abort...");
- KVMARM_NOT_IMPLEMENTED();
- return -EINVAL;
+ return io_mem_abort(vcpu, run, fault_ipa, memslot);
}
--
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