Re: [PATCH v13 09/12] mm: x86: Invoke hypercall when page encryption status is changed

Borislav Petkov
2021-04-21T13:52:11Z

On Wed, Apr 21, 2021 at 12:12:13PM +0000, Ashish Kalra wrote:
> Yes, both have some common code, but it is only this page level/size
> ...

See below for what I mean. Diff ontop of yours.

> I see that early_set_memory_enc_dec() is also using a for loop, so which
> patches are you referring to ?

The SNP guest set has this pattern:

https://lkml.kernel.org/r/20210408114049.GI10192@zn.tnic

---

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index b1d59d2b3bf6..e823645101ee 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -232,6 +232,37 @@ void __init sev_setup_arch(void)
swiotlb_adjust_size(size);
}

+static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
+{
+ unsigned long pfn = 0;
+ pgprot_t prot;
+
+ switch (level) {
+ case PG_LEVEL_4K:
+ pfn = pte_pfn(*kpte);
+ prot = pte_pgprot(*kpte);
+ break;
+
+ case PG_LEVEL_2M:
+ pfn = pmd_pfn(*(pmd_t *)kpte);
+ prot = pmd_pgprot(*(pmd_t *)kpte);
+ break;
+
+ case PG_LEVEL_1G:
+ pfn = pud_pfn(*(pud_t *)kpte);
+ prot = pud_pgprot(*(pud_t *)kpte);
+ break;
+
+ default:
+ return 0;
+ }
+
+ if (ret_prot)
+ *ret_prot = prot;
+
+ return pfn;
+}
+
static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
bool enc)
{
@@ -249,19 +280,9 @@ static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
if (!kpte || pte_none(*kpte))
return;

- switch (level) {
- case PG_LEVEL_4K:
- pfn = pte_pfn(*kpte);
- break;
- case PG_LEVEL_2M:
- pfn = pmd_pfn(*(pmd_t *)kpte);
- break;
- case PG_LEVEL_1G:
- pfn = pud_pfn(*(pud_t *)kpte);
- break;
- default:
- return;
- }
+ pfn = pg_level_to_pfn(level, kpte, NULL);
+ if (!pfn)
+ continue;

psize = page_level_size(level);
pmask = page_level_mask(level);
@@ -279,22 +300,9 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
unsigned long pfn, pa, size;
pte_t new_pte;

- switch (level) {
- case PG_LEVEL_4K:
- pfn = pte_pfn(*kpte);
- old_prot = pte_pgprot(*kpte);
- break;
- case PG_LEVEL_2M:
- pfn = pmd_pfn(*(pmd_t *)kpte);
- old_prot = pmd_pgprot(*(pmd_t *)kpte);
- break;
- case PG_LEVEL_1G:
- pfn = pud_pfn(*(pud_t *)kpte);
- old_prot = pud_pgprot(*(pud_t *)kpte);
- break;
- default:
+ pfn = pg_level_to_pfn(level, kpte, &old_prot);
+ if (!pfn)
return;
- }

new_prot = old_prot;
if (enc)

--
Regards/Gruss,
Boris.