[PATCH v2] arm/arm64: KVM: MMIO support for BE guest
Anup Patel
anup at brainfault.org
Tue Oct 29 21:10:43 EDT 2013
On Wed, Oct 30, 2013 at 12:19 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> Do the necessary byteswap when host and guest have different
> views of the universe. Actually, the only case we need to take
> care of is when the guest is BE. All the other cases are naturally
> handled.
You might want to handle the case where we have LE guest on BE host
because for ARM64 kernel we might have lot of people interested in
running host kernel in BE mode with KVM enabled.
--
Anup
>
> Also be careful about endianness when the data is being memcopy-ed
> from/to the run buffer.
>
> Cc: Christoffer Dall <christoffer.dall at linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
> >From v1:
> - Moved data insertion/extraction into specific functions
> - Bit of tidying up making the patch more readable
>
> arch/arm/include/asm/kvm_emulate.h | 41 +++++++++++++++++
> arch/arm/kvm/mmio.c | 87 +++++++++++++++++++++++++++++++-----
> arch/arm64/include/asm/kvm_emulate.h | 48 ++++++++++++++++++++
> 3 files changed, 165 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index a464e8d..8a6be05 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -157,4 +157,45 @@ static inline u32 kvm_vcpu_hvc_get_imm(struct kvm_vcpu *vcpu)
> return kvm_vcpu_get_hsr(vcpu) & HSR_HVC_IMM_MASK;
> }
>
> +static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
> +{
> + return !!(*vcpu_cpsr(vcpu) & PSR_E_BIT);
> +}
> +
> +static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
> + unsigned long data,
> + unsigned int len)
> +{
> + if (kvm_vcpu_is_be(vcpu)) {
> + switch (len) {
> + case 1:
> + return data & 0xff;
> + case 2:
> + return be16_to_cpu(data & 0xffff);
> + default:
> + return be32_to_cpu(data);
> + }
> + }
> +
> + return data; /* Leave LE untouched */
> +}
> +
> +static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
> + unsigned long data,
> + unsigned int len)
> +{
> + if (kvm_vcpu_is_be(vcpu)) {
> + switch (len) {
> + case 1:
> + return data & 0xff;
> + case 2:
> + return cpu_to_be16(data & 0xffff);
> + default:
> + return cpu_to_be32(data);
> + }
> + }
> +
> + return data; /* Leave LE untouched */
> +}
> +
> #endif /* __ARM_KVM_EMULATE_H__ */
> diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
> index 0c25d94..54105f1b 100644
> --- a/arch/arm/kvm/mmio.c
> +++ b/arch/arm/kvm/mmio.c
> @@ -23,6 +23,69 @@
>
> #include "trace.h"
>
> +static void mmio_write_data(struct kvm_exit_mmio *mmio, unsigned long data)
> +{
> + void *datap = NULL;
> + union {
> + u8 byte;
> + u16 hword;
> + u32 word;
> + u64 dword;
> + } tmp;
> +
> + switch (mmio->len) {
> + case 1:
> + tmp.byte = data;
> + datap = &tmp.byte;
> + break;
> + case 2:
> + tmp.hword = data;
> + datap = &tmp.hword;
> + break;
> + case 4:
> + tmp.word = data;
> + datap = &tmp.word;
> + break;
> + case 8:
> + tmp.dword = data;
> + datap = &tmp.dword;
> + break;
> + }
> +
> + memcpy(mmio->data, datap, mmio->len);
> +}
> +
> +static unsigned long mmio_read_data(struct kvm_run *run)
> +{
> + unsigned long data = 0;
> + unsigned int len = run->mmio.len;
> + union {
> + u16 hword;
> + u32 word;
> + u64 dword;
> + } tmp;
> +
> + switch (len) {
> + case 1:
> + data = run->mmio.data[0];
> + break;
> + case 2:
> + memcpy(&tmp.hword, run->mmio.data, len);
> + data = tmp.hword;
> + break;
> + case 4:
> + memcpy(&tmp.word, run->mmio.data, len);
> + data = tmp.word;
> + break;
> + case 8:
> + memcpy(&tmp.dword, run->mmio.data, len);
> + data = tmp.dword;
> + break;
> + }
> +
> + return data;
> +}
> +
> /**
> * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
> * @vcpu: The VCPU pointer
> @@ -33,28 +96,27 @@
> */
> int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> - unsigned long *dest;
> + unsigned long data;
> unsigned int len;
> int mask;
>
> if (!run->mmio.is_write) {
> - dest = vcpu_reg(vcpu, vcpu->arch.mmio_decode.rt);
> - *dest = 0;
> -
> len = run->mmio.len;
> if (len > sizeof(unsigned long))
> return -EINVAL;
>
> - memcpy(dest, run->mmio.data, len);
> -
> - trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
> - *((u64 *)run->mmio.data));
> + data = mmio_read_data(run);
>
> if (vcpu->arch.mmio_decode.sign_extend &&
> len < sizeof(unsigned long)) {
> mask = 1U << ((len * 8) - 1);
> - *dest = (*dest ^ mask) - mask;
> + data = (data ^ mask) - mask;
> }
> +
> + trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
> + data);
> + data = vcpu_data_host_to_guest(vcpu, data, len);
> + *vcpu_reg(vcpu, vcpu->arch.mmio_decode.rt) = data;
> }
>
> return 0;
> @@ -105,6 +167,7 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
> phys_addr_t fault_ipa)
> {
> struct kvm_exit_mmio mmio;
> + unsigned long data;
> unsigned long rt;
> int ret;
>
> @@ -125,13 +188,15 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
> }
>
> rt = vcpu->arch.mmio_decode.rt;
> + data = vcpu_data_guest_to_host(vcpu, *vcpu_reg(vcpu, rt), mmio.len);
> +
> trace_kvm_mmio((mmio.is_write) ? KVM_TRACE_MMIO_WRITE :
> KVM_TRACE_MMIO_READ_UNSATISFIED,
> mmio.len, fault_ipa,
> - (mmio.is_write) ? *vcpu_reg(vcpu, rt) : 0);
> + (mmio.is_write) ? data : 0);
>
> if (mmio.is_write)
> - memcpy(mmio.data, vcpu_reg(vcpu, rt), mmio.len);
> + mmio_write_data(&mmio, data);
>
> if (vgic_handle_mmio(vcpu, run, &mmio))
> return 1;
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index eec0738..3a7d058 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -177,4 +177,52 @@ static inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
> return kvm_vcpu_get_hsr(vcpu) & ESR_EL2_FSC_TYPE;
> }
>
> +static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu_mode_is_32bit(vcpu))
> + return !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_E_BIT);
> +
> + return !!(vcpu_sys_reg(vcpu, SCTLR_EL1) & (1 << 25));
> +}
> +
> +static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
> + unsigned long data,
> + unsigned int len)
> +{
> + if (kvm_vcpu_is_be(vcpu)) {
> + switch (len) {
> + case 1:
> + return data & 0xff;
> + case 2:
> + return be16_to_cpu(data & 0xffff);
> + case 4:
> + return be32_to_cpu(data & ((1UL << 32) - 1));
> + default:
> + return be64_to_cpu(data);
> + }
> + }
> +
> + return data; /* Leave LE untouched */
> +}
> +
> +static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
> + unsigned long data,
> + unsigned int len)
> +{
> + if (kvm_vcpu_is_be(vcpu)) {
> + switch (len) {
> + case 1:
> + return data & 0xff;
> + case 2:
> + return cpu_to_be16(data & 0xffff);
> + case 4:
> + return cpu_to_be32(data & ((1UL << 32) - 1));
> + default:
> + return cpu_to_be64(data);
> + }
> + }
> +
> + return data; /* Leave LE untouched */
> +}
> +
> #endif /* __ARM64_KVM_EMULATE_H__ */
> --
> 1.8.2.3
>
>
>
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