From 6f51114b0ead04e51594d367328481ae21a55bcb Mon Sep 17 00:00:00 2001 From: Ivan Klokov Date: Tue, 21 Nov 2023 10:17:57 +0300 Subject: [PATCH] target/riscv/cpu_helper.c: Fix mxr bit behavior According to RISCV Specification sect 9.5 on two stage translation when V=1 the vsstatus(mstatus in QEMU's terms) field MXR, which makes execute-only pages readable, only overrides VS-stage page protection. Setting MXR at HS-level(mstatus_hs), however, overrides both VS-stage and G-stage execute-only permissions. The hypervisor extension changes the behavior of MXR\MPV\MPRV bits. Due to RISCV Specification sect. 9.4.1 when MPRV=1, explicit memory accesses are translated and protected, and endianness is applied, as though the current virtualization mode were set to MPV and the current nominal privilege mode were set to MPP. vsstatus.MXR makes readable those pages marked executable at the VS translation stage. Fixes: 36a18664ba ("target/riscv: Implement second stage MMU") Signed-off-by: Ivan Klokov Reviewed-by: Alistair Francis Reviewed-by: Daniel Henrique Barboza Message-ID: <20231121071757.7178-3-ivan.klokov@syntacore.com> Signed-off-by: Alistair Francis (cherry picked from commit 6bca4d7d1ff2b8857486c3ff31f5c6fc3e3984b4) Signed-off-by: Michael Tokarev --- target/riscv/cpu_helper.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c index 3c482f9fd4..ce10d722f1 100644 --- a/target/riscv/cpu_helper.c +++ b/target/riscv/cpu_helper.c @@ -989,13 +989,29 @@ restart: prot |= PAGE_WRITE; } if (pte & PTE_X) { - bool mxr; + bool mxr = false; - if (first_stage == true) { + /* + * Use mstatus for first stage or for the second stage without + * virt_enabled (MPRV+MPV) + */ + if (first_stage || !env->virt_enabled) { mxr = get_field(env->mstatus, MSTATUS_MXR); - } else { - mxr = get_field(env->vsstatus, MSTATUS_MXR); } + + /* MPRV+MPV case, check VSSTATUS */ + if (first_stage && two_stage && !env->virt_enabled) { + mxr |= get_field(env->vsstatus, MSTATUS_MXR); + } + + /* + * Setting MXR at HS-level overrides both VS-stage and G-stage + * execute-only permissions + */ + if (env->virt_enabled) { + mxr |= get_field(env->mstatus_hs, MSTATUS_MXR); + } + if (mxr) { prot |= PAGE_READ; }