From: Christoffer Dall christoffer.dall@arm.com

On AArch64 you can do a sign-extended load to either a 32-bit or 64-bit register, and we should only sign extend the register up to the width of the register as specified in the operation (by using the 32-bit Wn or 64-bit Xn register specifier).

As it turns out, the architecture provides this decoding information in the SF ("Sixty-Four" -- how cute...) bit.

Let's take advantage of this with the usual 32-bit/64-bit header file dance and do the right thing on AArch64 hosts.

Signed-off-by: Christoffer Dall christoffer.dall@arm.com Signed-off-by: Marc Zyngier maz@kernel.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20191212195055.5541-1-christoffer.dall@arm.com --- arch/arm/include/asm/kvm_emulate.h | 5 +++++ arch/arm/include/asm/kvm_mmio.h | 2 ++ arch/arm64/include/asm/kvm_emulate.h | 5 +++++ arch/arm64/include/asm/kvm_mmio.h | 6 ++---- virt/kvm/arm/mmio.c | 6 ++++++ 5 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h index 9b118516d2db..fe55d8737a11 100644 --- a/arch/arm/include/asm/kvm_emulate.h +++ b/arch/arm/include/asm/kvm_emulate.h @@ -182,6 +182,11 @@ static inline bool kvm_vcpu_dabt_issext(struct kvm_vcpu *vcpu) return kvm_vcpu_get_hsr(vcpu) & HSR_SSE; }

+static inline bool kvm_vcpu_dabt_issf(const struct kvm_vcpu *vcpu) +{ + return false; +} + static inline int kvm_vcpu_dabt_get_rd(struct kvm_vcpu *vcpu) { return (kvm_vcpu_get_hsr(vcpu) & HSR_SRT_MASK) >> HSR_SRT_SHIFT; diff --git a/arch/arm/include/asm/kvm_mmio.h b/arch/arm/include/asm/kvm_mmio.h index 7c0eddb0adb2..32fbf82e3ebc 100644 --- a/arch/arm/include/asm/kvm_mmio.h +++ b/arch/arm/include/asm/kvm_mmio.h @@ -14,6 +14,8 @@ struct kvm_decode { unsigned long rt; bool sign_extend; + /* Not used on 32-bit arm */ + bool sixty_four; };

void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data); diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index 5efe5ca8fecf..f407b6bdad2e 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -283,6 +283,11 @@ static inline bool kvm_vcpu_dabt_issext(const struct kvm_vcpu *vcpu) return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SSE); }

+static inline bool kvm_vcpu_dabt_issf(const struct kvm_vcpu *vcpu) +{ + return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SF); +} + static inline int kvm_vcpu_dabt_get_rd(const struct kvm_vcpu *vcpu) { return (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT; diff --git a/arch/arm64/include/asm/kvm_mmio.h b/arch/arm64/include/asm/kvm_mmio.h index 02b5c48fd467..b204501a0c39 100644 --- a/arch/arm64/include/asm/kvm_mmio.h +++ b/arch/arm64/include/asm/kvm_mmio.h @@ -10,13 +10,11 @@ #include <linux/kvm_host.h> #include <asm/kvm_arm.h>

-/* - * This is annoying. The mmio code requires this, even if we don't - * need any decoding. To be fixed. - */ struct kvm_decode { unsigned long rt; bool sign_extend; + /* Witdth of the register accessed by the faulting instruction is 64-bits */ + bool sixty_four; };

void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data); diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c index 70d3b449692c..1bb71acd53f2 100644 --- a/virt/kvm/arm/mmio.c +++ b/virt/kvm/arm/mmio.c @@ -105,6 +105,9 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run) data = (data ^ mask) - mask; }

+ if (!vcpu->arch.mmio_decode.sixty_four) + data = data & 0xffffffff; + trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr, &data); data = vcpu_data_host_to_guest(vcpu, data, len); @@ -125,6 +128,7 @@ static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len) unsigned long rt; int access_size; bool sign_extend; + bool sixty_four;

if (kvm_vcpu_dabt_iss1tw(vcpu)) { /* page table accesses IO mem: tell guest to fix its TTBR */ @@ -138,11 +142,13 @@ static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)

*is_write = kvm_vcpu_dabt_iswrite(vcpu); sign_extend = kvm_vcpu_dabt_issext(vcpu); + sixty_four = kvm_vcpu_dabt_issf(vcpu); rt = kvm_vcpu_dabt_get_rd(vcpu);

*len = access_size; vcpu->arch.mmio_decode.sign_extend = sign_extend; vcpu->arch.mmio_decode.rt = rt; + vcpu->arch.mmio_decode.sixty_four = sixty_four;

return 0; }