Re: [RESEND PATCH v21 5/6] target-arm: kvm64: handle SIGBUS signal from kernel or KVM

[Xiang Zheng <zhengxiang9@huawei.com>]

Hi Beata,

Thanks for you review!

On 2019/11/22 23:47, Beata Michalska wrote:
> Hi,
> 
> On Mon, 11 Nov 2019 at 01:48, Xiang Zheng <zhengxiang9@huawei.com> wrote:
>>
>> From: Dongjiu Geng <gengdongjiu@huawei.com>
>>
>> Add a SIGBUS signal handler. In this handler, it checks the SIGBUS type,
>> translates the host VA delivered by host to guest PA, then fills this PA
>> to guest APEI GHES memory, then notifies guest according to the SIGBUS
>> type.
>>
>> When guest accesses the poisoned memory, it will generate a Synchronous
>> External Abort(SEA). Then host kernel gets an APEI notification and calls
>> memory_failure() to unmapped the affected page in stage 2, finally
>> returns to guest.
>>
>> Guest continues to access the PG_hwpoison page, it will trap to KVM as
>> stage2 fault, then a SIGBUS_MCEERR_AR synchronous signal is delivered to
>> Qemu, Qemu records this error address into guest APEI GHES memory and
>> notifes guest using Synchronous-External-Abort(SEA).
>>
>> In order to inject a vSEA, we introduce the kvm_inject_arm_sea() function
>> in which we can setup the type of exception and the syndrome information.
>> When switching to guest, the target vcpu will jump to the synchronous
>> external abort vector table entry.
>>
>> The ESR_ELx.DFSC is set to synchronous external abort(0x10), and the
>> ESR_ELx.FnV is set to not valid(0x1), which will tell guest that FAR is
>> not valid and hold an UNKNOWN value. These values will be set to KVM
>> register structures through KVM_SET_ONE_REG IOCTL.
>>
>> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
>> Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com>
>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>  hw/acpi/acpi_ghes.c         | 297 ++++++++++++++++++++++++++++++++++++
>>  include/hw/acpi/acpi_ghes.h |   4 +
>>  include/sysemu/kvm.h        |   3 +-
>>  target/arm/cpu.h            |   4 +
>>  target/arm/helper.c         |   2 +-
>>  target/arm/internals.h      |   5 +-
>>  target/arm/kvm64.c          |  64 ++++++++
>>  target/arm/tlb_helper.c     |   2 +-
>>  target/i386/cpu.h           |   2 +
>>  9 files changed, 377 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/acpi/acpi_ghes.c b/hw/acpi/acpi_ghes.c
>> index 42c00ff3d3..f5b54990c0 100644
>> --- a/hw/acpi/acpi_ghes.c
>> +++ b/hw/acpi/acpi_ghes.c
>> @@ -39,6 +39,34 @@
>>  /* The max size in bytes for one error block */
>>  #define ACPI_GHES_MAX_RAW_DATA_LENGTH       0x1000
>>
>> +/*
>> + * The total size of Generic Error Data Entry
>> + * ACPI 6.1/6.2: 18.3.2.7.1 Generic Error Data,
>> + * Table 18-343 Generic Error Data Entry
>> + */
>> +#define ACPI_GHES_DATA_LENGTH               72
>> +
>> +/*
>> + * The memory section CPER size,
>> + * UEFI 2.6: N.2.5 Memory Error Section
>> + */
>> +#define ACPI_GHES_MEM_CPER_LENGTH           80
>> +
>> +/*
>> + * Masks for block_status flags
>> + */
>> +#define ACPI_GEBS_UNCORRECTABLE         1
> 
> Why not listing all supported statuses ? Similar to error severity below ?
> 

We now only use the first bit for uncorrectable error. The correctable errors
are handled in host and would not be delivered to QEMU.

I think it's unnecessary to list all the bit masks.

>> +
>> +/*
>> + * Values for error_severity field
>> + */
>> +enum AcpiGenericErrorSeverity {
>> +    ACPI_CPER_SEV_RECOVERABLE,
>> +    ACPI_CPER_SEV_FATAL,
>> +    ACPI_CPER_SEV_CORRECTED,
>> +    ACPI_CPER_SEV_NONE,
>> +};
>> +
>>  /*
>>   * Now only support ARMv8 SEA notification type error source
>>   */
>> @@ -49,6 +77,16 @@
>>   */
>>  #define ACPI_GHES_SOURCE_GENERIC_ERROR_V2   10
>>
>> +#define UUID_BE(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)        \
>> +    {{{ ((a) >> 24) & 0xff, ((a) >> 16) & 0xff, ((a) >> 8) & 0xff, (a) & 0xff, \
>> +    ((b) >> 8) & 0xff, (b) & 0xff,                   \
>> +    ((c) >> 8) & 0xff, (c) & 0xff,                    \
>> +    (d0), (d1), (d2), (d3), (d4), (d5), (d6), (d7) } } }
>> +
>> +#define UEFI_CPER_SEC_PLATFORM_MEM                   \
>> +    UUID_BE(0xA5BC1114, 0x6F64, 0x4EDE, 0xB8, 0x63, 0x3E, 0x83, \
>> +    0xED, 0x7C, 0x83, 0xB1)
>> +
>>  /*
>>   * | +--------------------------+ 0
>>   * | |        Header            |
>> @@ -77,6 +115,174 @@ typedef struct AcpiGhesState {
>>      uint64_t ghes_addr_le;
>>  } AcpiGhesState;
>>
>> +/*
>> + * Total size for Generic Error Status Block
>> + * ACPI 6.2: 18.3.2.7.1 Generic Error Data,
>> + * Table 18-380 Generic Error Status Block
>> + */
>> +#define ACPI_GHES_GESB_SIZE                 20
> 
> Minor: This is not entirely correct: GEDE is part of GESB so the total length
> would be ACPI_GHES_GESB_SIZE + n* sizeof(GEDE)
> 

Yes, here it only indicates the total length of Generic Error Status Block structure
expect "GEDEs".

>> +/* The offset of Data Length in Generic Error Status Block */
>> +#define ACPI_GHES_GESB_DATA_LENGTH_OFFSET   12
>> +
> 
> If those were nicely represented as structures you get the offsets easily
> without having number of defines. That could simplify the code and make it
> more readable - see comments below
> 

To address Igor's comment, this macro is useless and I will drop it.

>> +/*
>> + * Record the value of data length for each error status block to avoid getting
>> + * this value from guest.
>> + */
>> +static uint32_t acpi_ghes_data_length[ACPI_GHES_ERROR_SOURCE_COUNT];
>> +
>> +/*
>> + * Generic Error Data Entry
>> + * ACPI 6.1: 18.3.2.7.1 Generic Error Data
>> + */
>> +static void acpi_ghes_generic_error_data(GArray *table, QemuUUID section_type,
>> +                uint32_t error_severity, uint16_t revision,
>> +                uint8_t validation_bits, uint8_t flags,
>> +                uint32_t error_data_length, QemuUUID fru_id,
>> +                uint8_t *fru_text, uint64_t time_stamp)
> 
> Why not just defining a struct that represents the GED entry?
> 
>> +{
>> +    QemuUUID uuid_le;
>> +
>> +    /* Section Type */
>> +    uuid_le = qemu_uuid_bswap(section_type);
>> +    g_array_append_vals(table, uuid_le.data, ARRAY_SIZE(uuid_le.data));
>> +
>> +    /* Error Severity */
>> +    build_append_int_noprefix(table, error_severity, 4);
>> +    /* Revision */
>> +    build_append_int_noprefix(table, revision, 2);
> 
> Minor: According to the spec it seems that the revision number is
> a fixed value so you could drop that from the parameters....
> or ... use a struct to represent the data
> 
>> +    /* Validation Bits */
>> +    build_append_int_noprefix(table, validation_bits, 1);
>> +    /* Flags */
>> +    build_append_int_noprefix(table, flags, 1);
>> +    /* Error Data Length */
>> +    build_append_int_noprefix(table, error_data_length, 4);
>> +
>> +    /* FRU Id */
>> +    uuid_le = qemu_uuid_bswap(fru_id);
>> +    g_array_append_vals(table, uuid_le.data, ARRAY_SIZE(uuid_le.data));
>> +
>> +    /* FRU Text */
>> +    g_array_append_vals(table, fru_text, 20);
>> +    /* Timestamp */
>> +    build_append_int_noprefix(table, time_stamp, 8);
>> +}
>> +
>> +/*
>> + * Generic Error Status Block
>> + * ACPI 6.1: 18.3.2.7.1 Generic Error Data
>> + */
>> +static void acpi_ghes_generic_error_status(GArray *table, uint32_t block_status,
>> +                uint32_t raw_data_offset, uint32_t raw_data_length,
>> +                uint32_t data_length, uint32_t error_severity)
> 
> Same as the above
> 

>> +{
>> +    /* Block Status */
>> +    build_append_int_noprefix(table, block_status, 4);
>> +    /* Raw Data Offset */
>> +    build_append_int_noprefix(table, raw_data_offset, 4);
>> +    /* Raw Data Length */
>> +    build_append_int_noprefix(table, raw_data_length, 4);
>> +    /* Data Length */
>> +    build_append_int_noprefix(table, data_length, 4);
>> +    /* Error Severity */
>> +    build_append_int_noprefix(table, error_severity, 4);
>> +}
>> +
>> +/* UEFI 2.6: N.2.5 Memory Error Section */
>> +static void acpi_ghes_build_append_mem_cper(GArray *table,
>> +                                            uint64_t error_physical_addr)
>> +{
>> +    /*
>> +     * Memory Error Record
>> +     */
>> +
>> +    /* Validation Bits */
>> +    build_append_int_noprefix(table,
>> +                              (1UL << 14) | /* Type Valid */
>> +                              (1UL << 1) /* Physical Address Valid */,
>> +                              8);
>> +    /* Error Status */
>> +    build_append_int_noprefix(table, 0, 8);
> 
> Just wondering whether it would be worth to specify the Error Type
> through the Error Status ?
> 

Error Status relies on the informations from implementation-specific error registers
which means we need to provide more informations to QEMU to handle.

In current implemention, KVM only delivers BUS_MCEERR_AR type of signal and poisoned
HVA to userspace(QEMU). If we want to extract more information in QEMU, it requires KVM
to provide corresponding informations. However KVM is not ready for that now.

>> +    /* Physical Address */
>> +    build_append_int_noprefix(table, error_physical_addr, 8);
>> +    /* Skip all the detailed information normally found in such a record */
>> +    build_append_int_noprefix(table, 0, 48);
>> +    /* Memory Error Type */
>> +    build_append_int_noprefix(table, 0 /* Unknown error */, 1);
>> +    /* Skip all the detailed information normally found in such a record */
>> +    build_append_int_noprefix(table, 0, 7);
>> +}
>> +
>> +static int acpi_ghes_record_mem_error(uint64_t error_block_address,
>> +                                      uint64_t error_physical_addr,
>> +                                      uint32_t data_length)
>> +{
>> +    GArray *block;
>> +    uint64_t current_block_length;
>> +    /* Memory Error Section Type */
>> +    QemuUUID mem_section_id_le = UEFI_CPER_SEC_PLATFORM_MEM;
> 
> As already mentioned - mixing LE /w BE
> 

>> +    QemuUUID fru_id = {};
>> +    uint8_t fru_text[20] = {};
>> +
>> +    /*
>> +     * Generic Error Status Block
>> +     * | +---------------------+
>> +     * | |     block_status    |
>> +     * | +---------------------+
>> +     * | |    raw_data_offset  |
>> +     * | +---------------------+
>> +     * | |    raw_data_length  |
>> +     * | +---------------------+
>> +     * | |     data_length     |
>> +     * | +---------------------+
>> +     * | |   error_severity    |
>> +     * | +---------------------+
>> +     */
>> +    block = g_array_new(false, true /* clear */, 1);
>> +
>> +    /* The current whole length of the generic error status block */
>> +    current_block_length = ACPI_GHES_GESB_SIZE + data_length;
>> +
>> +    /* This is the length if adding a new generic error data entry*/
>> +    data_length += ACPI_GHES_DATA_LENGTH;
>> +    data_length += ACPI_GHES_MEM_CPER_LENGTH;
>> +
>> +    /*
>> +     * Check whether it will run out of the preallocated memory if adding a new
>> +     * generic error data entry
>> +     */
>> +    if ((data_length + ACPI_GHES_GESB_SIZE) > ACPI_GHES_MAX_RAW_DATA_LENGTH) {
>> +        error_report("Record CPER out of boundary!!!");
> 
> Minor: The error message could be made more accurate, like:
>     "Not enough memory to record new CPER"
> 

OK.

>> +        return ACPI_GHES_CPER_FAIL;
>> +    }
>> +
>> +    /* Build the new generic error status block header */
>> +    acpi_ghes_generic_error_status(block, cpu_to_le32(ACPI_GEBS_UNCORRECTABLE),
>> +        0, 0, cpu_to_le32(data_length), cpu_to_le32(ACPI_CPER_SEV_RECOVERABLE));
>> +
>> +    /* Write back above generic error status block header to guest memory */
>> +    cpu_physical_memory_write(error_block_address, block->data,
>> +                              block->len);
>> +
>> +    /* Add a new generic error data entry */
>> +
>> +    data_length = block->len;
>> +    /* Build this new generic error data entry header */
>> +    acpi_ghes_generic_error_data(block, mem_section_id_le,
>> +        cpu_to_le32(ACPI_CPER_SEV_RECOVERABLE), cpu_to_le32(0x300), 0, 0,
>> +        cpu_to_le32(ACPI_GHES_MEM_CPER_LENGTH), fru_id, fru_text, 0);
>> +
>> +    /* Build the memory section CPER for above new generic error data entry */
>> +    acpi_ghes_build_append_mem_cper(block, error_physical_addr);
>> +
>> +    /* Write back above this new generic error data entry to guest memory */
>> +    cpu_physical_memory_write(error_block_address + current_block_length,
>> +        block->data + data_length, block->len - data_length);
>> +
> 
> As already mentioned and unless I have missed smth (which is highly possible)
> this will append new records while the GESB is kept 'in-place'. So the
> used space is
> only growing.
> 

Yes, we need to address this unlimited growing records.

>> +    g_array_free(block, true);
>> +
>> +    return ACPI_GHES_CPER_OK;
>> +}
>> +
>>  /*
>>   * Hardware Error Notification
>>   * ACPI 4.0: 17.3.2.7 Hardware Error Notification
>> @@ -265,3 +471,94 @@ void acpi_ghes_add_fw_cfg(FWCfgState *s, GArray *hardware_error)
>>      fw_cfg_add_file_callback(s, ACPI_GHES_DATA_ADDR_FW_CFG_FILE, NULL, NULL,
>>          NULL, &ges.ghes_addr_le, sizeof(ges.ghes_addr_le), false);
>>  }
>> +
>> +bool acpi_ghes_record_errors(uint32_t notify, uint64_t physical_address)
>> +{
>> +    uint64_t error_block_addr, read_ack_register_addr, read_ack_register = 0;
>> +    int loop = 0;
>> +    uint64_t start_addr = le64_to_cpu(ges.ghes_addr_le);
>> +    bool ret = ACPI_GHES_CPER_FAIL;
>> +    uint8_t source_id;
>> +    const uint8_t error_source_id[] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
>> +                                        0xff, 0xff,    0, 0xff, 0xff, 0xff};
>> +
> 
> I'm not entirely sure why this is needed - se below
> 

>> +    /*
>> +     * | +---------------------+ ges.ghes_addr_le
>> +     * | |error_block_address0 |
>> +     * | +---------------------+ --+--
>> +     * | |    .............    | ACPI_GHES_ADDRESS_SIZE
>> +     * | +---------------------+ --+--
>> +     * | |error_block_addressN |
>> +     * | +---------------------+
>> +     * | | read_ack_register0  |
>> +     * | +---------------------+ --+--
>> +     * | |   .............     | ACPI_GHES_ADDRESS_SIZE
>> +     * | +---------------------+ --+--
>> +     * | | read_ack_registerN  |
>> +     * | +---------------------+ --+--
>> +     * | |      CPER           |   |
>> +     * | |      ....           | ACPI_GHES_MAX_RAW_DATA_LENGT
>> +     * | |      CPER           |   |
>> +     * | +---------------------+ --+--
>> +     * | |    ..........       |
>> +     * | +---------------------+
>> +     * | |      CPER           |
>> +     * | |      ....           |
>> +     * | |      CPER           |
>> +     * | +---------------------+
>> +     */
>> +    if (physical_address && notify < ACPI_GHES_NOTIFY_RESERVED) {
>> +        /* Find and check the source id for this new CPER */
>> +        source_id = error_source_id[notify];
> 
> Why not using switch case for supported source types ?
> For the time being only one is being supported. And you only use that to
> verify that support - seems a bit unnecessary.
> 

Good idea, I think using switch case is much better.

>> +        if (source_id != 0xff) {
>> +            start_addr += source_id * ACPI_GHES_ADDRESS_SIZE;
>> +        } else {
>> +            goto out;
>> +        }
>> +
>> +        cpu_physical_memory_read(start_addr, &error_block_addr,
>> +                                 ACPI_GHES_ADDRESS_SIZE);
>> +
>> +        read_ack_register_addr = start_addr +
>> +            ACPI_GHES_ERROR_SOURCE_COUNT * ACPI_GHES_ADDRESS_SIZE;
>> +retry:
>> +        cpu_physical_memory_read(read_ack_register_addr,
>> +                                 &read_ack_register, ACPI_GHES_ADDRESS_SIZE);
>> +
>> +        /* zero means OSPM does not acknowledge the error */
>> +        if (!read_ack_register) {
>> +            if (loop < 3) {
>> +                usleep(100 * 1000);
>> +                loop++;
>> +                goto retry;
>> +            } else {
>> +                error_report("OSPM does not acknowledge previous error,"
>> +                    " so can not record CPER for current error, forcibly"
>> +                    " acknowledge previous error to avoid blocking next time"
>> +                    " CPER record! Exit");
>> +                read_ack_register = 1;
>> +                cpu_physical_memory_write(read_ack_register_addr,
>> +                    &read_ack_register, ACPI_GHES_ADDRESS_SIZE);
> 
> Already mentioned ...
> This seems to be against the spec. It not only ignores the req
> for OSPM to acknowledge receiving notifications for previous errors ,
> but it also loses one of them. Why not caching it somewhere until
> OSPM acknowledges the old ones ?
> 

Yes, Igor had mentioned this point in the previous comments.

>> +            }
>> +        } else {
>> +            if (error_block_addr) {
> 
> What is the use case for the address not being set ?
> 

Hmmm...I'd add a "error_fatal" in this case.

>> +                read_ack_register = 0;
>> +                /*
>> +                 * Clear the Read Ack Register, OSPM will write it to 1 when
>> +                 * acknowledge this error.
>> +                 */
>> +                cpu_physical_memory_write(read_ack_register_addr,
>> +                    &read_ack_register, ACPI_GHES_ADDRESS_SIZE);
> 
> If the ack register has been cleared - which is why we end up here ....
> why writing it back if there is no notification for the system to process ?
> 

Ending up here means the ack register has been acked by OSPM, we need to clear it so
that OSPM can write it back to 1 at the next time.

>> +                ret = acpi_ghes_record_mem_error(error_block_addr,
>> +                          physical_address, acpi_ghes_data_length[source_id]);
>> +                if (ret == ACPI_GHES_CPER_OK) {
>> +                    acpi_ghes_data_length[source_id] +=
>> +                        (ACPI_GHES_DATA_LENGTH + ACPI_GHES_MEM_CPER_LENGTH);
> 
> As mentioned .. this will run out of space - some roll-back
> mechanism is needed to overwrite stale entries
> 

Yes, Igor had mentioned this point too.

>> +                }
>> +            }
>> +        }
>> +    }
>> +
>> +out:
>> +    return ret;
>> +}
>> diff --git a/include/hw/acpi/acpi_ghes.h b/include/hw/acpi/acpi_ghes.h
>> index cb62ec9c7b..8e3c5b879e 100644
>> --- a/include/hw/acpi/acpi_ghes.h
>> +++ b/include/hw/acpi/acpi_ghes.h
>> @@ -24,6 +24,9 @@
>>
>>  #include "hw/acpi/bios-linker-loader.h"
>>
>> +#define ACPI_GHES_CPER_OK                   1
>> +#define ACPI_GHES_CPER_FAIL                 0
>> +
> 
> Is there really a need to introduce those ?
> 

Don't you think it's more clear than using "1" or "0"? :)

>>  /*
>>   * Values for Hardware Error Notification Type field
>>   */
>> @@ -53,4 +56,5 @@ void acpi_ghes_build_hest(GArray *table_data, GArray *hardware_error,
>>
>>  void acpi_ghes_build_error_table(GArray *hardware_errors, BIOSLinker *linker);
>>  void acpi_ghes_add_fw_cfg(FWCfgState *s, GArray *hardware_errors);
>> +bool acpi_ghes_record_errors(uint32_t notify, uint64_t error_physical_addr);
>>  #endif
> 
> All the above should preferably land in a separate patch
> 

OK.

>> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
>> index 9d143282bc..321ead8115 100644
>> --- a/include/sysemu/kvm.h
>> +++ b/include/sysemu/kvm.h
>> @@ -378,8 +378,7 @@ bool kvm_vcpu_id_is_valid(int vcpu_id);
>>  /* Returns VCPU ID to be used on KVM_CREATE_VCPU ioctl() */
>>  unsigned long kvm_arch_vcpu_id(CPUState *cpu);
>>
>> -#ifdef TARGET_I386
>> -#define KVM_HAVE_MCE_INJECTION 1
>> +#ifdef KVM_HAVE_MCE_INJECTION
>>  void kvm_arch_on_sigbus_vcpu(CPUState *cpu, int code, void *addr);
>>  #endif
>>
>> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
>> index d844ea21d8..c4fe6ccc63 100644
>> --- a/target/arm/cpu.h
>> +++ b/target/arm/cpu.h
>> @@ -28,6 +28,10 @@
>>  /* ARM processors have a weak memory model */
>>  #define TCG_GUEST_DEFAULT_MO      (0)
>>
>> +#ifdef TARGET_AARCH64
>> +#define KVM_HAVE_MCE_INJECTION 1
>> +#endif
>> +
>>  #define EXCP_UDEF            1   /* undefined instruction */
>>  #define EXCP_SWI             2   /* software interrupt */
>>  #define EXCP_PREFETCH_ABORT  3
>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>> index 63815fc4cf..a9ce97efb1 100644
>> --- a/target/arm/helper.c
>> +++ b/target/arm/helper.c
>> @@ -3005,7 +3005,7 @@ static uint64_t do_ats_write(CPUARMState *env, uint64_t value,
>>               * Report exception with ESR indicating a fault due to a
>>               * translation table walk for a cache maintenance instruction.
>>               */
>> -            syn = syn_data_abort_no_iss(current_el == target_el,
>> +            syn = syn_data_abort_no_iss(current_el == target_el, 0,
>>                                          fi.ea, 1, fi.s1ptw, 1, fsc);
>>              env->exception.vaddress = value;
>>              env->exception.fsr = fsr;
>> diff --git a/target/arm/internals.h b/target/arm/internals.h
>> index f5313dd3d4..28b8451d6d 100644
>> --- a/target/arm/internals.h
>> +++ b/target/arm/internals.h
>> @@ -451,13 +451,14 @@ static inline uint32_t syn_insn_abort(int same_el, int ea, int s1ptw, int fsc)
>>          | ARM_EL_IL | (ea << 9) | (s1ptw << 7) | fsc;
>>  }
>>
>> -static inline uint32_t syn_data_abort_no_iss(int same_el,
>> +static inline uint32_t syn_data_abort_no_iss(int same_el, int fnv,
>>                                               int ea, int cm, int s1ptw,
>>                                               int wnr, int fsc)
>>  {
>>      return (EC_DATAABORT << ARM_EL_EC_SHIFT) | (same_el << ARM_EL_EC_SHIFT)
>>             | ARM_EL_IL
>> -           | (ea << 9) | (cm << 8) | (s1ptw << 7) | (wnr << 6) | fsc;
>> +           | (fnv << 10) | (ea << 9) | (cm << 8) | (s1ptw << 7)
>> +           | (wnr << 6) | fsc;
>>  }
>>
>>  static inline uint32_t syn_data_abort_with_iss(int same_el,
>> diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
>> index 28f6db57d5..c7b7653d3f 100644
>> --- a/target/arm/kvm64.c
>> +++ b/target/arm/kvm64.c
>> @@ -28,6 +28,8 @@
>>  #include "kvm_arm.h"
>>  #include "hw/boards.h"
>>  #include "internals.h"
>> +#include "hw/acpi/acpi.h"
>> +#include "hw/acpi/acpi_ghes.h"
>>
>>  static bool have_guest_debug;
>>
>> @@ -710,6 +712,30 @@ int kvm_arm_cpreg_level(uint64_t regidx)
>>      return KVM_PUT_RUNTIME_STATE;
>>  }
>>
>> +/* Callers must hold the iothread mutex lock */
>> +static void kvm_inject_arm_sea(CPUState *c)
> 
> We could enclose this function along with the kvm_arch_on_sigbus_vcpu
> within ifdef switch for KVM_HAVE_MCE_INJECTION
> 

Peter suggested to define KVM_HAVE_MCE_INJECTION within ifdef TARGET_AARCH64.
So isn't KVM_HAVE_MCE_INJECTION always defined in the target/arm/kvm64.c?

>> +{
>> +    ARMCPU *cpu = ARM_CPU(c);
>> +    CPUARMState *env = &cpu->env;
>> +    CPUClass *cc = CPU_GET_CLASS(c);
>> +    uint32_t esr;
>> +    bool same_el;
>> +
>> +    c->exception_index = EXCP_DATA_ABORT;
>> +    env->exception.target_el = 1;
>> +
>> +    /*
>> +     * Set the DFSC to synchronous external abort and set FnV to not valid,
>> +     * this will tell guest the FAR_ELx is UNKNOWN for this abort.
>> +     */
>> +    same_el = arm_current_el(env) == env->exception.target_el;
>> +    esr = syn_data_abort_no_iss(same_el, 1, 0, 0, 0, 0, 0x10);
> 
> IINM this is the only use case when FnV is considered to be valid
> so I'm not convinced it is worth to modify the syn_data_abort_no_iss
> just for this.
> 
>> +
>> +    env->exception.syndrome = esr;
>> +
>> +    cc->do_interrupt(c);
>> +}
>> +
>>  #define AARCH64_CORE_REG(x)   (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
>>                   KVM_REG_ARM_CORE | KVM_REG_ARM_CORE_REG(x))
>>
>> @@ -1036,6 +1062,44 @@ int kvm_arch_get_registers(CPUState *cs)
>>      return ret;
>>  }
>>
>> +void kvm_arch_on_sigbus_vcpu(CPUState *c, int code, void *addr)
>> +{
>> +    ram_addr_t ram_addr;
>> +    hwaddr paddr;
>> +
>> +    assert(code == BUS_MCEERR_AR || code == BUS_MCEERR_AO);
>> +
>> +    if (acpi_enabled && addr &&
>> +            object_property_get_bool(qdev_get_machine(), "ras", NULL)) {
>> +        ram_addr = qemu_ram_addr_from_host(addr);
>> +        if (ram_addr != RAM_ADDR_INVALID &&
>> +            kvm_physical_memory_addr_from_host(c->kvm_state, addr, &paddr)) {
>> +            kvm_hwpoison_page_add(ram_addr);
>> +            /*
>> +             * Asynchronous signal will be masked by main thread, so
>> +             * only handle synchronous signal.
>> +             */
> 
> I'm not entirely sure that the comment above is correct (it has been
> pointed out before). I would expect the AO signal to be handled here as
> well. Not having proper support to do that just yet is another story but
> the comment might be bit misleading.
> 

We also expect the AO signal can be handled here. Maybe we could add the comment like:

"Asynchronous signal is masked by main thread now. Once it can be asserted, we could
handle it." :)

> 
>> +            if (code == BUS_MCEERR_AR) {
>> +                kvm_cpu_synchronize_state(c);
>> +                if (ACPI_GHES_CPER_FAIL !=
>> +                    acpi_ghes_record_errors(ACPI_GHES_NOTIFY_SEA, paddr)) {
>> +                    kvm_inject_arm_sea(c);
>> +                } else {
>> +                    fprintf(stderr, "failed to record the error\n");
>> +                }
>> +            }
>> +            return;
>> +        }
>> +        fprintf(stderr, "Hardware memory error for memory used by "
>> +                "QEMU itself instead of guest system!\n");
>> +    }
>> +
>> +    if (code == BUS_MCEERR_AR) {
>> +        fprintf(stderr, "Hardware memory error!\n");
>> +        exit(1);
>> +    }
>> +}
>> +
>>  /* C6.6.29 BRK instruction */
>>  static const uint32_t brk_insn = 0xd4200000;
>>
>> diff --git a/target/arm/tlb_helper.c b/target/arm/tlb_helper.c
>> index 5feb312941..499672ebbc 100644
>> --- a/target/arm/tlb_helper.c
>> +++ b/target/arm/tlb_helper.c
>> @@ -33,7 +33,7 @@ static inline uint32_t merge_syn_data_abort(uint32_t template_syn,
>>       * ISV field.
>>       */
>>      if (!(template_syn & ARM_EL_ISV) || target_el != 2 || s1ptw) {
>> -        syn = syn_data_abort_no_iss(same_el,
>> +        syn = syn_data_abort_no_iss(same_el, 0,
>>                                      ea, 0, s1ptw, is_write, fsc);
>>      } else {
>>          /*
>> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
>> index 5352c9ff55..f75a210f96 100644
>> --- a/target/i386/cpu.h
>> +++ b/target/i386/cpu.h
>> @@ -29,6 +29,8 @@
>>  /* The x86 has a strong memory model with some store-after-load re-ordering */
>>  #define TCG_GUEST_DEFAULT_MO      (TCG_MO_ALL & ~TCG_MO_ST_LD)
>>
>> +#define KVM_HAVE_MCE_INJECTION 1
>> +
>>  /* Maximum instruction code size */
>>  #define TARGET_MAX_INSN_SIZE 16
>>
>> --
>> 2.19.1
>>
>>
>>
> 
> .
> 

-- 

Thanks,
Xiang