On 8/17/21 12:27 PM, Borislav Petkov wrote:

The majority of kernel code puts __packed after the struct definition,
let's put it there too pls, out of the way.

...

Noted.

quoted

+		if (WARN(ret || ghcb->save.sw_exit_info_2,
+			 "SEV-SNP: page state change failed ret=%d exit_info_2=%llx\n",
+			 ret, ghcb->save.sw_exit_info_2))
+			return 1;

Yikes, you return here and below with interrupts disabled.

All your returns need to be "goto out;" instead where you do

out:
         __sev_put_ghcb(&state);
         local_irq_restore(flags);

Yap, you very likely need to put the GHCB too.

Sure, let me revisit this code to fix those path.

quoted

+		/*
+		 * Lets do some sanity check that entry processing is not going
+		 * backward. This will happen only if hypervisor is tricking us.
+		 */
+		if (WARN((hdr->end_entry > end_entry) || (cur_entry > hdr->cur_entry),
+			"SEV-SNP: page state change processing going backward, end_entry "
+			"(expected %d got %d) cur_entry (expected %d got %d)\n",
+			end_entry, hdr->end_entry, cur_entry, hdr->cur_entry))
+			return 1;

WARNING: quoted string split across lines
#293: FILE: arch/x86/kernel/sev.c:750:
+			"SEV-SNP: page state change processing going backward, end_entry "
+			"(expected %d got %d) cur_entry (expected %d got %d)\n",

If you're wondering what to do, yes, you can really stretch that string
and shorten it too:

Okay.

                 if (WARN((hdr->end_entry > end_entry) || (cur_entry > hdr->cur_entry),
"SEV-SNP: PSC processing going backwards, end_entry %d (got %d) cur_entry: %d (got %d)\n",
                          end_entry, hdr->end_entry, cur_entry, hdr->cur_entry))
                         return 1;

so that it fits on a single line and grepping can find it.

Noted.

quoted

+		/* Lets verify that reserved bit is not set in the header*/
+		if (WARN(hdr->reserved, "Reserved bit is set in the PSC header\n"))

psc_entry has a ->reserved field too and since we're iterating over the
entries...

Sure I can add that check.

quoted

+
+	desc = kmalloc(sizeof(*desc), GFP_KERNEL_ACCOUNT);

kzalloc() so that you don't have to memset() later in
__set_page_state().

Depending on the size, the __set_page_state() can be call multiple times 
so it should clear the desc memory before filling it.

quoted

+	if (!desc)
+		panic("failed to allocate memory");

Make that error message more distinctive so that *if* it happens, one
can pinpoint the place in the code where the panic comes from.

Now I am running checkpatch and notice that it complain about the 
message too. I can add a BUG() or WARN() to get the stack trace before 
the crashing.

quoted

+	while (vaddr < vaddr_end) {
+		/*
+		 * Calculate the last vaddr that can be fit in one
+		 * struct snp_psc_desc.
+		 */
+		next_vaddr = min_t(unsigned long, vaddr_end,
+				(VMGEXIT_PSC_MAX_ENTRY * PAGE_SIZE) + vaddr);
+
+		__set_page_state(desc, vaddr, next_vaddr, op);
+
+		vaddr = next_vaddr;
+	}
+
+	kfree(desc);
+}
+