> Is there any way we can move the above code to target-s390x? Having the > branch below is already invasive enough for generic code, but we really > don't need all the special s390 quirks to live here.
Hmm, we have to have a special hook somehow. What about this approach? ----------------------- 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 <borntrae...@de.ibm.com> --- exec.c | 19 ++++--------------- kvm.h | 1 + oslib-posix.c | 3 +++ target-s390x/kvm.c | 34 ++++++++++++++++++++++++++++++++++ 4 files changed, 42 insertions(+), 15 deletions(-) diff --git a/exec.c b/exec.c index a587e7a..9b9b8e1 100644 --- a/exec.c +++ b/exec.c @@ -2645,26 +2645,15 @@ 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); +#if defined(TARGET_S390X) + } else if (kvm_enabled()) { + new_block->host = kvm_arch_alloc(size); +#endif } 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..9d50016 100644 --- a/kvm.h +++ b/kvm.h @@ -102,6 +102,7 @@ int kvm_vcpu_ioctl(CPUArchState *env, int type, ...); extern const KVMCapabilityInfo kvm_arch_required_capabilities[]; +void *kvm_arch_alloc(ram_addr_t size); void kvm_arch_pre_run(CPUArchState *env, struct kvm_run *run); void kvm_arch_post_run(CPUArchState *env, struct kvm_run *run); 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..ccf5daa 100644 --- a/target-s390x/kvm.c +++ b/target-s390x/kvm.c @@ -135,6 +135,40 @@ int kvm_arch_get_registers(CPUS390XState *env) return 0; } +/* + * 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; +} + +void *kvm_arch_alloc(ram_addr_t size) +{ + if (kvm_check_extension(kvm_state, KVM_CAP_S390_GMAP) && + kvm_check_extension(kvm_state, KVM_CAP_S390_COW)) { + return qemu_vmalloc(size); + } else { + return legacy_s390_alloc(size); + } +} + int kvm_arch_insert_sw_breakpoint(CPUS390XState *env, struct kvm_sw_breakpoint *bp) { static const uint8_t diag_501[] = {0x83, 0x24, 0x05, 0x01};