Re: [PATCH v6 69/76] x86/realmode: Setup AP jump table

Borislav Petkov
2020-08-31T17:09:48Z

On Mon, Aug 24, 2020 at 10:55:04AM +0200, Joerg Roedel wrote:
> diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
> index 8f36ae021a7f..a19ce9681ec2 100644
> --- a/arch/x86/include/uapi/asm/svm.h
> +++ b/arch/x86/include/uapi/asm/svm.h
> @@ -84,6 +84,9 @@
> /* SEV-ES software-defined VMGEXIT events */
> #define SVM_VMGEXIT_MMIO_READ 0x80000001
> #define SVM_VMGEXIT_MMIO_WRITE 0x80000002
> +#define SVM_VMGEXIT_AP_JUMP_TABLE 0x80000005
> +#define SVM_VMGEXIT_SET_AP_JUMP_TABLE 0
> +#define SVM_VMGEXIT_GET_AP_JUMP_TABLE 1
^^^^^^^^^^^^

One tab too many here.

> #define SVM_VMGEXIT_UNSUPPORTED_EVENT 0x8000ffff
>
> #define SVM_EXIT_ERR -1
> diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
> index 28fe95ecd508..09a45ccd6c1d 100644
> --- a/arch/x86/kernel/sev-es.c
> +++ b/arch/x86/kernel/sev-es.c
> @@ -21,6 +21,8 @@
> #include <linux/mm.h>
>
> #include <asm/cpu_entry_area.h>
> +#include <asm/stacktrace.h>
> +#include <asm/realmode.h>
> #include <asm/sev-es.h>
> #include <asm/insn-eval.h>
> #include <asm/fpu/internal.h>
> @@ -219,6 +221,9 @@ static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
> }
> }
>
> +/* Needed in vc_early_vc_forward_exception */

vc_early_forward_exception()

> +void do_early_exception(struct pt_regs *regs, int trapnr);
> +
> static inline u64 sev_es_rd_ghcb_msr(void)
> {
> return native_read_msr(MSR_AMD64_SEV_ES_GHCB);
> @@ -407,6 +412,69 @@ static bool vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
> /* Include code shared with pre-decompression boot stage */
> #include "sev-es-shared.c"
>
> +static u64 sev_es_get_jump_table_addr(void)

Static and used here only once - you can drop the previx "sev_es".

> +{
> + struct ghcb_state state;
> + unsigned long flags;
> + struct ghcb *ghcb;
> + u64 ret;
> +
> + local_irq_save(flags);
> +
> + ghcb = sev_es_get_ghcb(&state);
> +
> + vc_ghcb_invalidate(ghcb);
> + ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_JUMP_TABLE);
> + ghcb_set_sw_exit_info_1(ghcb, SVM_VMGEXIT_GET_AP_JUMP_TABLE);
> + ghcb_set_sw_exit_info_2(ghcb, 0);
> +
> + sev_es_wr_ghcb_msr(__pa(ghcb));
> + VMGEXIT();
> +
> + if (!ghcb_sw_exit_info_1_is_valid(ghcb) ||
> + !ghcb_sw_exit_info_2_is_valid(ghcb))
> + ret = 0;
> +
> + ret = ghcb->save.sw_exit_info_2;
> +
> + sev_es_put_ghcb(&state);
> +
> + local_irq_restore(flags);
> +
> + return ret;
> +}
> +
> +int sev_es_setup_ap_jump_table(struct real_mode_header *rmh)
> +{
> + u16 startup_cs, startup_ip;
> + phys_addr_t jump_table_pa;
> + u64 jump_table_addr;
> + u16 __iomem *jump_table;
> +
> + jump_table_addr = sev_es_get_jump_table_addr();
> +
> + /* Check if AP Jump Table is non-zero and page-aligned */
> + if (!jump_table_addr || jump_table_addr & ~PAGE_MASK)
> + return 0;

I think you need to return !0 here so that the panic() below fires with
a modified message:

panic("Failed to get/update SEV-ES AP Jump Table");

or are we gonna boot an UP guest still?

If not panic, at least a warning that at least some APs didn't come
up...

--
Regards/Gruss,
Boris.