Mangle the memory attribute register values at each write to MAIR_EL1 so that regions that the guest intends to map as device or uncached are in fact mapped as cached instead. This avoids incoherency issues when the guest bypassed the caches to access memory that the host has mapped as cached.
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> --- arch/arm64/kvm/sys_regs.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 1e170eab6603..bde2b49a7cd8 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -110,6 +110,39 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu, return true; } +static bool access_mair(struct kvm_vcpu *vcpu, + const struct sys_reg_params *p, + const struct sys_reg_desc *r) +{ + unsigned long val, mask; + + BUG_ON(!p->is_write); + + val = *vcpu_reg(vcpu, p->Rt); + + if (!p->is_aarch32) { + /* + * Mangle val so that all device and uncached attributes are + * replaced with cached attributes. + * For each attribute, check whether any of bit 7, bit 5 or bit + * 4 are set. If not, it is a device or outer non-cacheable + * mapping and we override it with inner, outer write-through, + * read+write-allocate (0xbb). + * TODO: handle outer cacheable inner non-cacheable + */ + mask = ~(val >> 7 | val >> 5 | val >> 4) & 0x0101010101010101UL; + val = (val & ~(mask * 0xff)) | (mask * 0xbb); + + vcpu_sys_reg(vcpu, r->reg) = val; + } else { + if (!p->is_32bit) + vcpu_cp15_64_high(vcpu, r->reg) = val >> 32; + vcpu_cp15_64_low(vcpu, r->reg) = val & 0xffffffffUL; + } + + return true; +} + static bool trap_raz_wi(struct kvm_vcpu *vcpu, const struct sys_reg_params *p, const struct sys_reg_desc *r) @@ -371,7 +404,7 @@ static const struct sys_reg_desc sys_reg_descs[] = { /* MAIR_EL1 */ { Op0(0b11), Op1(0b000), CRn(0b1010), CRm(0b0010), Op2(0b000), - access_vm_reg, reset_unknown, MAIR_EL1 }, + access_mair, reset_unknown, MAIR_EL1 }, /* AMAIR_EL1 */ { Op0(0b11), Op1(0b000), CRn(0b1010), CRm(0b0011), Op2(0b000), access_handled_at_el2, reset_amair_el1, AMAIR_EL1 }, -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html