Re: [Qemu-devel] [PATCH v9 26/27] gdbstub: Add support to read a MSR for KVM target

[Alex Bennée]

Jon Doron <address@hidden> writes:

> gdb> maint packet qqemu.kvm.Rdmsr:MsrIndex

gdbserver already has a mechanism for exposing system registers see:

  commit 200bf5b7ffea635079cc05fdfb363372b9544ce7
  Author: Abdallah Bouassida <address@hidden>
  Date:   Fri May 18 17:48:07 2018 +0100

for an example. As MSR's are very specific to x86 all this should be
handled via target/i386/gdbstub and kept out of the generic code.

>
> Signed-off-by: Jon Doron <address@hidden>
> ---
>  gdbstub.c | 38 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index 34da10260d..f48c3a2b5f 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -2141,7 +2141,14 @@ static void handle_query_attached(GdbCmdContext 
> *gdb_ctx, void *user_ctx)
>
>  static void handle_query_qemu_supported(GdbCmdContext *gdb_ctx, void 
> *user_ctx)
>  {
> -    put_packet(gdb_ctx->s, "sstepbits;sstep;PhyMemMode");
> +    snprintf(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf),
> +             "sstepbits;sstep;PhyMemMode");
> +
> +    if (kvm_enabled()) {
> +        pstrcat(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), ";kvm.Rdmsr");
> +    }
> +
> +    put_packet(gdb_ctx->s, gdb_ctx->str_buf);
>  }
>
>  static void handle_query_qemu_phy_mem_mode(GdbCmdContext *gdb_ctx,
> @@ -2166,6 +2173,29 @@ static void handle_set_qemu_phy_mem_mode(GdbCmdContext 
> *gdb_ctx, void *user_ctx)
>      put_packet(gdb_ctx->s, "OK");
>  }
>
> +static void handle_query_kvm_read_msr(GdbCmdContext *gdb_ctx, void *user_ctx)
> +{
> +    uint64_t msr_val;
> +
> +    if (!kvm_enabled()) {
> +        return;
> +    }
> +
> +    if (!gdb_ctx->num_params) {
> +        put_packet(gdb_ctx->s, "E22");
> +        return;
> +    }
> +
> +    if (kvm_arch_read_msr(gdbserver_state->c_cpu, gdb_ctx->params[0].val_ul,
> +                          &msr_val)) {
> +        put_packet(gdb_ctx->s, "E00");
> +        return;
> +    }
> +
> +    snprintf(gdb_ctx->str_buf, sizeof(gdb_ctx->str_buf), "0x%" PRIx64, 
> msr_val);
> +    put_packet(gdb_ctx->s, gdb_ctx->str_buf);
> +}
> +
>  static GdbCmdParseEntry gdb_gen_query_set_common_table[] = {
>      /* Order is important if has same prefix */
>      {
> @@ -2250,6 +2280,12 @@ static GdbCmdParseEntry gdb_gen_query_table[] = {
>          .handler = handle_query_qemu_phy_mem_mode,
>          .cmd = "qemu.PhyMemMode",
>      },
> +    {
> +        .handler = handle_query_kvm_read_msr,
> +        .cmd = "qemu.kvm.Rdmsr:",
> +        .cmd_startswith = 1,
> +        .schema = "l0"
> +    },
>  };
>
>  static GdbCmdParseEntry gdb_gen_set_table[] = {


--
Alex Bennée