From f52bfb12143e29d7c8bd827bdb751aee47a9694e Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 16 Oct 2017 22:23:57 +0200 Subject: accel/tcg: allow to invalidate a write TLB entry immediately Background: s390x implements Low-Address Protection (LAP). If LAP is enabled, writing to effective addresses (before any translation) 0-511 and 4096-4607 triggers a protection exception. So we have subpage protection on the first two pages of every address space (where the lowcore - the CPU private data resides). By immediately invalidating the write entry but allowing the caller to continue, we force every write access onto these first two pages into the slow path. we will get a tlb fault with the specific accessed addresses and can then evaluate if protection applies or not. We have to make sure to ignore the invalid bit if tlb_fill() succeeds. Signed-off-by: David Hildenbrand Message-Id: <20171016202358.3633-2-david@redhat.com> Signed-off-by: Cornelia Huck --- accel/tcg/cputlb.c | 5 ++++- accel/tcg/softmmu_template.h | 4 ++-- include/exec/cpu-all.h | 3 +++ 3 files changed, 9 insertions(+), 3 deletions(-) diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c index 5b1ef14..a23919c 100644 --- a/accel/tcg/cputlb.c +++ b/accel/tcg/cputlb.c @@ -694,6 +694,9 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr, } else { tn.addr_write = address; } + if (prot & PAGE_WRITE_INV) { + tn.addr_write |= TLB_INVALID_MASK; + } } /* Pairs with flag setting in tlb_reset_dirty_range */ @@ -978,7 +981,7 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr, if (!VICTIM_TLB_HIT(addr_write, addr)) { tlb_fill(ENV_GET_CPU(env), addr, MMU_DATA_STORE, mmu_idx, retaddr); } - tlb_addr = tlbe->addr_write; + tlb_addr = tlbe->addr_write & ~TLB_INVALID_MASK; } /* Check notdirty */ diff --git a/accel/tcg/softmmu_template.h b/accel/tcg/softmmu_template.h index d756329..3fc5144 100644 --- a/accel/tcg/softmmu_template.h +++ b/accel/tcg/softmmu_template.h @@ -285,7 +285,7 @@ void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val, if (!VICTIM_TLB_HIT(addr_write, addr)) { tlb_fill(ENV_GET_CPU(env), addr, MMU_DATA_STORE, mmu_idx, retaddr); } - tlb_addr = env->tlb_table[mmu_idx][index].addr_write; + tlb_addr = env->tlb_table[mmu_idx][index].addr_write & ~TLB_INVALID_MASK; } /* Handle an IO access. */ @@ -361,7 +361,7 @@ void helper_be_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val, if (!VICTIM_TLB_HIT(addr_write, addr)) { tlb_fill(ENV_GET_CPU(env), addr, MMU_DATA_STORE, mmu_idx, retaddr); } - tlb_addr = env->tlb_table[mmu_idx][index].addr_write; + tlb_addr = env->tlb_table[mmu_idx][index].addr_write & ~TLB_INVALID_MASK; } /* Handle an IO access. */ diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h index 778031c..0b14168 100644 --- a/include/exec/cpu-all.h +++ b/include/exec/cpu-all.h @@ -245,6 +245,9 @@ extern intptr_t qemu_host_page_mask; /* original state of the write flag (used when tracking self-modifying code */ #define PAGE_WRITE_ORG 0x0010 +/* Invalidate the TLB entry immediately, helpful for s390x + * Low-Address-Protection. Used with PAGE_WRITE in tlb_set_page_with_attrs() */ +#define PAGE_WRITE_INV 0x0040 #if defined(CONFIG_BSD) && defined(CONFIG_USER_ONLY) /* FIXME: Code that sets/uses this is broken and needs to go away. */ #define PAGE_RESERVED 0x0020 -- cgit v1.1