Hi Julien,
On 19/06/2024 13:55, Julien Grall wrote:
>
>
> Hi Michal,
>
> On 19/06/2024 07:46, Michal Orzel wrote:
>> Building Xen with CONFIG_STATIC_SHM=y results in a build failure:
>>
>> arch/arm/static-shmem.c: In function 'process_shm':
>> arch/arm/static-shmem.c:327:41: error: 'gbase' may be used uninitialized
>> [-Werror=maybe-uninitialized]
>> 327 | if ( is_domain_direct_mapped(d) && (pbase != gbase) )
>> arch/arm/static-shmem.c:305:17: note: 'gbase' was declared here
>> 305 | paddr_t gbase, pbase, psize;
>>
>> This is because the commit cb1ddafdc573 adds a check referencing
>> gbase/pbase variables which were not yet assigned a value. Fix it.
>>
>> Fixes: cb1ddafdc573 ("xen/arm/static-shmem: Static-shmem should be
>> direct-mapped for direct-mapped domains")
>> Signed-off-by: Michal Orzel <michal.or...@amd.com>
>> ---
>> Rationale for 4.19: this patch fixes a build failure reported by CI:
>> https://gitlab.com/xen-project/xen/-/jobs/7131807878
>> ---
>> xen/arch/arm/static-shmem.c | 13 +++++++------
>> 1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/xen/arch/arm/static-shmem.c b/xen/arch/arm/static-shmem.c
>> index c434b96e6204..cd48d2896b7e 100644
>> --- a/xen/arch/arm/static-shmem.c
>> +++ b/xen/arch/arm/static-shmem.c
>> @@ -324,12 +324,6 @@ int __init process_shm(struct domain *d, struct
>> kernel_info *kinfo,
>> printk("%pd: static shared memory bank not found: '%s'", d,
>> shm_id);
>> return -ENOENT;
>> }
>> - if ( is_domain_direct_mapped(d) && (pbase != gbase) )
>> - {
>> - printk("%pd: physical address 0x%"PRIpaddr" and guest address
>> 0x%"PRIpaddr" are not direct-mapped.\n",
>> - d, pbase, gbase);
>> - return -EINVAL;
>> - }
>>
>> pbase = boot_shm_bank->start;
>> psize = boot_shm_bank->size;
>> @@ -353,6 +347,13 @@ int __init process_shm(struct domain *d, struct
>> kernel_info *kinfo,
>> /* guest phys address is after host phys address */
>> gbase = dt_read_paddr(cells + addr_cells, addr_cells);
>>
>> + if ( is_domain_direct_mapped(d) && (pbase != gbase) )
>> + {
>> + printk("%pd: physical address 0x%"PRIpaddr" and guest
>> address 0x%"PRIpaddr" are not direct-mapped.\n",
>> + d, pbase, gbase);
>> + return -EINVAL;
>> + }
>> +
>
> Before this patch, the check was globally. I guess the intention was it
> covers the two part of the "if". But now, you only have it in when
> "paddr" is specified in the DT.
>
> From a brief look at the code, I can't figure out why we don't need a
> similar check on the else path. Is this because it is guarantee that
> will be paddr == gaddr?
The reason why I added this check only in the first case is due to what doc
states.
It says that if a domain is 1:1, the shmem should be also 1:1 i.e. pbase ==
gbase. In the else
case the pbase is omitted and thus a user cannot know and has no guarantee what
will be the backing physical address.
Thus, reading this doc makes me feel that for 1:1 guests user needs to specify
pbase == gbase.
~Michal
