drivers/virt: pkvm: Don't fail ioremap() call if MMIO_GUARD fails

[ Upstream commit d44679fb954ffea961036ed1aeb7d65035f78489 ]

Calling the MMIO_GUARD hypercall from guests which have not been
enrolled (e.g. because they are running without pvmfw) results in
-EINVAL being returned. In this case, MMIO_GUARD is not active
and so we can simply proceed with the normal ioremap() routine.

Don't fail ioremap() if MMIO_GUARD fails; instead WARN_ON_ONCE()
to highlight that the pvm environment is slightly wonky.

Fixes: 0f12694958 ("drivers/virt: pkvm: Intercept ioremap using pKVM MMIO_GUARD hypercall")
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20241202145731.6422-2-will@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c

@@ -87,12 +87,8 @@ static int mmio_guard_ioremap_hook(phys_addr_t phys, size_t size,
 
 	while (phys < end) {
 		const int func_id = ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_FUNC_ID;
-		int err;
-
-		err = arm_smccc_do_one_page(func_id, phys);
-		if (err)
-			return err;
 
+		WARN_ON_ONCE(arm_smccc_do_one_page(func_id, phys));
 		phys += PAGE_SIZE;
 	}