From 07d79fe7c22364de34618e58b92a8f091bd7e03d Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Tue, 31 Oct 2017 15:51:18 +0000 Subject: arm64/sve: KVM: Hide SVE from CPU features exposed to guests MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit KVM guests cannot currently use SVE, because SVE is always configured to trap to EL2. However, a guest that sees SVE reported as present in ID_AA64PFR0_EL1 may legitimately expect that SVE works and try to use it. Instead of working, the guest will receive an injected undef exception, which may cause the guest to oops or go into a spin. To avoid misleading the guest into believing that SVE will work, this patch masks out the SVE field from ID_AA64PFR0_EL1 when a guest attempts to read this register. No support is explicitly added for ID_AA64ZFR0_EL1 either, so that is still emulated as reading as zero, which is consistent with SVE not being implemented. This is a temporary measure, and will be removed in a later series when full KVM support for SVE is implemented. Signed-off-by: Dave Martin Reviewed-by: Alex Bennée Acked-by: Marc Zyngier Acked-by: Catalin Marinas Acked-by: Christoffer Dall Signed-off-by: Will Deacon --- arch/arm64/kvm/sys_regs.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index b1f75522177c..a0ee9b05e3d4 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include @@ -897,8 +898,17 @@ static u64 read_id_reg(struct sys_reg_desc const *r, bool raz) { u32 id = sys_reg((u32)r->Op0, (u32)r->Op1, (u32)r->CRn, (u32)r->CRm, (u32)r->Op2); + u64 val = raz ? 0 : read_sanitised_ftr_reg(id); - return raz ? 0 : read_sanitised_ftr_reg(id); + if (id == SYS_ID_AA64PFR0_EL1) { + if (val & (0xfUL << ID_AA64PFR0_SVE_SHIFT)) + pr_err_once("kvm [%i]: SVE unsupported for guests, suppressing\n", + task_pid_nr(current)); + + val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT); + } + + return val; } /* cpufeature ID register access trap handlers */ -- cgit