On 6/24/2024 1:26 PM, Borislav Petkov wrote:
>> @@ -92,6 +94,9 @@ static struct ghcb *boot_ghcb __section(".data");
>> /* Bitmap of SEV features supported by the hypervisor */
>> static u64 sev_hv_features __ro_after_init;
>>
>> +/* Last address to be switched to private during kexec */
>> +static unsigned long kexec_last_addr_to_make_private;
> This is particularly yucky.
>
> AFAIU, you want to:
>
> 1. Skip GHCB addresses when making all pages private
>
> 2. Once you're done converting, in snp_kexec_finish() go over the GHCB
> addresses and convert them explicitly, one-by-one, without this silly
> variable
it is simple to compare the current CPU's GHCB while walking the direct
mapping, OTOH, comparing each and every address during unshare_all_memory()
with all per-CPU GHCB addresses will just make it complicated and less
performant too.
By skipping only the current CPU's GHCB and saving a reference to it, we are
able to switch this (one) skipped GHCB page to private at the end of
kexec_finish().
>
>> /* #VC handler runtime per-CPU data */
>> struct sev_es_runtime_data {
>> struct ghcb ghcb_page;
>> @@ -1010,6 +1015,169 @@ void snp_accept_memory(phys_addr_t start,
>> phys_addr_t end)
>> set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
>> }
>>
>> +static bool set_pte_enc(pte_t *kpte, int level, void *va)
> Code duplication: __set_clr_pte_enc().
>
> You need to refactor the code instead of adding just another, generically
> looking helper just because it is easier this way.
The issue with using __set_clr_pte_enc() is that it is called by early
initialization code, it uses early_snp_set_memory_private() which uses the MSR
protocol for making page state change calls as early_set_pages_state() can be
called during early init code before the GHCB is established.
Hence, added simple static functions make_pte_private() and set_pte_enc() to
make use of the more optimized snp_set_memory_private() to use the GHCB instead
of the MSR protocol. Additionally, make_pte_private() adds check for GHCB
addresses during unshare_all_memory() loop.
Thanks, Ashish
>> + * at the end of unshared loop so that we continue to use the
>> + * optimized GHCB protocol and not force the switch to
>> + * MSR protocol till the very end.
>> + */
>>
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