Re: [RFC PATCH] target/i386: restrict SEV to 64 bit host builds

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 26/6/24 16:20, Daniel P. Berrangé wrote:
> On Wed, Jun 26, 2024 at 03:03:07PM +0100, Alex Bennée wrote:
>> Re-enabling the 32 bit host build on i686 showed the recently merged
>> SEV code doesn't take enough care over its types. While the format
>> strings could use more portable types there isn't much we can do about
>> casting uint64_t into a pointer. The easiest solution seems to be just
>> to disable SEV for a 32 bit build. It's highly unlikely anyone would
>> want this functionality anyway.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>>   target/i386/sev.h       | 2 +-
>>   target/i386/meson.build | 4 ++--
>>   2 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/target/i386/sev.h b/target/i386/sev.h
>> index 858005a119..b0cb9dd7ed 100644
>> --- a/target/i386/sev.h
>> +++ b/target/i386/sev.h
>> @@ -45,7 +45,7 @@ typedef struct SevKernelLoaderContext {
>>       size_t cmdline_size;
>>   } SevKernelLoaderContext;
>>   
>> -#ifdef CONFIG_SEV
>> +#if defined(CONFIG_SEV) && defined(HOST_X86_64)
>>   bool sev_enabled(void);
>>   bool sev_es_enabled(void);
>>   bool sev_snp_enabled(void);
>> diff --git a/target/i386/meson.build b/target/i386/meson.build
>> index 075117989b..d2a008926c 100644
>> --- a/target/i386/meson.build
>> +++ b/target/i386/meson.build
>> @@ -6,7 +6,7 @@ i386_ss.add(files(
>>     'xsave_helper.c',
>>     'cpu-dump.c',
>>   ))
>> -i386_ss.add(when: 'CONFIG_SEV', if_true: files('host-cpu.c', 'confidential-guest.c'))
>> +i386_ss.add(when: ['CONFIG_SEV', 'HOST_X86_64'], if_true: files('host-cpu.c', 'confidential-guest.c'))
>>   
>>   # x86 cpu type
>>   i386_ss.add(when: 'CONFIG_KVM', if_true: files('host-cpu.c'))
>> @@ -21,7 +21,7 @@ i386_system_ss.add(files(
>>     'cpu-apic.c',
>>     'cpu-sysemu.c',
>>   ))
>> -i386_system_ss.add(when: 'CONFIG_SEV', if_true: files('sev.c'), if_false: files('sev-sysemu-stub.c'))
>> +i386_system_ss.add(when: ['CONFIG_SEV', 'HOST_X86_64'], if_true: files('sev.c'), if_false: files('sev-sysemu-stub.c'))
>>   
>>   i386_user_ss = ss.source_set()
> 
> Instead of changing each usage of CONFIG_SEV, is it better to
> prevent it getting enabled in the first place ?
> 
> eg. move
> 
>    #CONFIG_SEV=n
> 
> From
> 
>    configs/devices/i386-softmmu/default.mak
> 
> to
> 
>    configs/devices/x86_64-softmmu/default.mak
> 
> And then also change
> 
>    hw/i386/Kconfig
> 
> to say
> 
>    config SEV
>        bool
>        select X86_FW_OVMF
>        depends on KVM && X86_64

Both are *targets*, IIUC we want to disable on *hosts*.