Re: [PATCH v2 06/10] i386/pc_sysfw: Ensure sysfw flash configuration does not conflict with IGVM

[Ani Sinha]

> On 3 Apr 2024, at 16:41, Roy Hopkins <roy.hopkins@suse.com> wrote:
> 
> When using an IGVM file the configuration of the system firmware is
> defined by IGVM directives contained in the file. In this case the user
> should not configure any pflash devices.
> 
> This commit skips initialization of the ROM mode when pflash0 is not set
> then checks to ensure no pflash devices have been configured when using
> IGVM, exiting with an error message if this is not the case.
> 
> Signed-off-by: Roy Hopkins <roy.hopkins@suse.com>
> ---
> hw/i386/pc_sysfw.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> index 3efabbbab2..2412f26225 100644
> --- a/hw/i386/pc_sysfw.c
> +++ b/hw/i386/pc_sysfw.c
> @@ -226,8 +226,13 @@ void pc_system_firmware_init(PCMachineState *pcms,
>     }
> 
>     if (!pflash_blk[0]) {
> -        /* Machine property pflash0 not set, use ROM mode */
> -        x86_bios_rom_init(MACHINE(pcms), "bios.bin", rom_memory, false);
> +        /*
> +         * Machine property pflash0 not set, use ROM mode unless using IGVM,
> +         * in which case the firmware must be provided by the IGVM file.

What if the igvm file does not contain a firmware? Can we have a check for that 
case somewhere and assert if firmware is absent?

> +         */
> +        if (!cgs_is_igvm(MACHINE(pcms)->cgs)) {
> +            x86_bios_rom_init(MACHINE(pcms), "bios.bin", rom_memory, false);
> +        }
>     } else {
>         if (kvm_enabled() && !kvm_readonly_mem_enabled()) {
>             /*
> @@ -243,6 +248,20 @@ void pc_system_firmware_init(PCMachineState *pcms,
>     }
> 
>     pc_system_flash_cleanup_unused(pcms);
> +
> +    /*
> +     * The user should not have specified any pflash devices when using IGVM
> +     * to configure the guest.
> +     */
> +    if (cgs_is_igvm(MACHINE(pcms)->cgs)) {
> +        for (i = 0; i < ARRAY_SIZE(pcms->flash); i++) {
> +            if (pcms->flash[i]) {
> +                error_report("pflash devices cannot be configured when "
> +                             "using IGVM");
> +                exit(1);
> +            }
> +        }
> +    }

I have not tested this change but looking at pc_system_flash_create() creates 
flash[0] and flash[1] for all cases (well except for isapc machines). So for 
igvm case, would this not cause an exit all the time?

> }
> 
> void x86_firmware_configure(void *ptr, int size)
> -- 
> 2.43.0
>