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X-Received-From: 195.75.94.111 Cc: Cornelia Huck , Christian Borntraeger , Jens Freimann , Heinz Graalfs , qemu-devel Subject: [Qemu-devel] [PATCH 2/8] s390: autodetect map private X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Christian Borntraeger By default qemu will use MAP_PRIVATE for guest pages. This will write protect pages and thus break on s390 systems that dont support this feature. Therefore qemu has a hack to always use MAP_SHARED for s390. But MAP_SHARED has other problems (no dirty pages tracking, a lot more swap overhead etc.) Newer systems allow the distinction via KVM_CAP_S390_COW. With this feature qemu can use the standard qemu alloc if available, otherwise it will use the old s390 hack. Signed-off-by: Christian Borntraeger Signed-off-by: Jens Freimann --- exec.c | 54 +++++++++++++++++++++++++++++++++++++--------------- kvm.h | 9 +++++++++ oslib-posix.c | 3 +++ target-s390x/kvm.c | 6 ++++++ 4 files changed, 57 insertions(+), 15 deletions(-) diff --git a/exec.c b/exec.c index a0494c7..8fec680 100644 --- a/exec.c +++ b/exec.c @@ -2618,6 +2618,43 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev) } } +/* + * lets make sure that we dont have the old s390x limitations regarding + * guest mappings + */ +static int legacy_s390x_mem_layout(void) +{ +#if defined(TARGET_S390X) + return kvm_has_legacy_s390x_memlayout(); +#else + return 0; +#endif +} + +/* + * Legacy layout for s390: + * Older S390 KVM requires the topmost vma of the RAM to be + * smaller than an system defined value, which is at least 256GB. + * Larger systems have larger values. We put the guest between + * the end of data segment (system break) and this value. We + * use 32GB as a base to have enough room for the system break + * to grow. We also have to use MAP parameters that avoid + * read-only mapping of guest pages. + */ +static void *legacy_s390_alloc(ram_addr_t size) +{ + void *mem; + + mem = mmap((void *) 0x800000000ULL, size, + PROT_EXEC|PROT_READ|PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0); + if (mem == MAP_FAILED) { + fprintf(stderr, "Allocating RAM failed\n"); + abort(); + } + return mem; +} + ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, MemoryRegion *mr) { @@ -2644,26 +2681,13 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, exit(1); #endif } else { -#if defined(TARGET_S390X) && defined(CONFIG_KVM) - /* S390 KVM requires the topmost vma of the RAM to be smaller than - an system defined value, which is at least 256GB. Larger systems - have larger values. We put the guest between the end of data - segment (system break) and this value. We use 32GB as a base to - have enough room for the system break to grow. */ - new_block->host = mmap((void*)0x800000000, size, - PROT_EXEC|PROT_READ|PROT_WRITE, - MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0); - if (new_block->host == MAP_FAILED) { - fprintf(stderr, "Allocating RAM failed\n"); - abort(); - } -#else if (xen_enabled()) { xen_ram_alloc(new_block->offset, size, mr); + } else if (legacy_s390x_mem_layout()) { + new_block->host = legacy_s390_alloc(size); } else { new_block->host = qemu_vmalloc(size); } -#endif qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE); } } diff --git a/kvm.h b/kvm.h index 9c7b0ea..ca0557e 100644 --- a/kvm.h +++ b/kvm.h @@ -62,6 +62,15 @@ int kvm_has_pit_state2(void); int kvm_has_many_ioeventfds(void); int kvm_has_gsi_routing(void); +#ifndef CONFIG_KVM +static inline int kvm_has_legacy_s390x_memlayout(void) +{ + return 0; +} +#else +int kvm_has_legacy_s390x_memlayout(void); +#endif + int kvm_allows_irq0_override(void); #ifdef NEED_CPU_H diff --git a/oslib-posix.c b/oslib-posix.c index b6a3c7f..93902ac 100644 --- a/oslib-posix.c +++ b/oslib-posix.c @@ -41,6 +41,9 @@ extern int daemon(int, int); therefore we need special code which handles running on Valgrind. */ # define QEMU_VMALLOC_ALIGN (512 * 4096) # define CONFIG_VALGRIND +#elif defined(__linux__) && defined(__s390x__) + /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */ +# define QEMU_VMALLOC_ALIGN (256 * 4096) #else # define QEMU_VMALLOC_ALIGN getpagesize() #endif diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c index 90aad61..93a8431 100644 --- a/target-s390x/kvm.c +++ b/target-s390x/kvm.c @@ -135,6 +135,12 @@ int kvm_arch_get_registers(CPUS390XState *env) return 0; } +int kvm_has_legacy_s390x_memlayout(void) +{ + return !kvm_check_extension(kvm_state, KVM_CAP_S390_GMAP) || + !kvm_check_extension(kvm_state, KVM_CAP_S390_COW); +} + int kvm_arch_insert_sw_breakpoint(CPUS390XState *env, struct kvm_sw_breakpoint *bp) { static const uint8_t diag_501[] = {0x83, 0x24, 0x05, 0x01};