Re: [kvm-unit-tests PATCH v2 1/8] s390x: uv-host: Add access checks for donated memory

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On 7/7/22 10:11, Steffen Eiden wrote:
Hi Janosch,

On 7/6/22 08:40, Janosch Frank wrote:
Let's check if the UV really protected all the memory we donated.

Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
---
   s390x/uv-host.c | 29 +++++++++++++++++++++++++++++
   1 file changed, 29 insertions(+)

diff --git a/s390x/uv-host.c b/s390x/uv-host.c
index a1a6d120..983cb4a1 100644
--- a/s390x/uv-host.c
+++ b/s390x/uv-host.c
@@ -43,6 +43,24 @@ static void cpu_loop(void)
   	for (;;) {}
   }
+/*
+ * Checks if a memory area is protected as secure memory.
+ * Will return true if all pages are protected, false otherwise.
+ */
+static bool access_check_3d(uint64_t *access_ptr, uint64_t len)
+{
+	while (len) {
+		expect_pgm_int();
+		*access_ptr += 42;
+		if (clear_pgm_int() != PGM_INT_CODE_SECURE_STOR_ACCESS)
+			return false;
+		access_ptr += PAGE_SIZE / sizeof(access_ptr);
+		len -= PAGE_SIZE;
If someone uses this function with 'len' not being a multiple of
PAGE_SIZE this test does not for what is was intended by testing more
memory than expected.

I suggest adding an explicit assert at the beginning of the function
that ensures 'len' is a multiple of PAGE_SIZE.

Sure


+	}
+
+	return true;
+}
+

[snip]

Steffen




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