commit a99bfa6f1f8aef215814f937fcd363b8907222a3
author Pierre-Clément Tosi <ptosi@google.com> Thu Oct 06 13:30:52 2022 +0100
committer Pierre-Clément Tosi <ptosi@google.com> Mon Oct 24 14:34:24 2022 +0100
tree c9639c8b6985f3846c5366fda4cfe6664a160a08
parent c522ec76573a540cdf0fa7f809f878691129c6f4

pvmfw: Issue MMIO_GUARD_UNMAP for UART

Ensure that the platform has been put back in its initial state by
unmapping the MMIO page that pvmfw used for logging.

Test: atest MicrodroidTestApp # currently broken without aosp/2238683
Change-Id: I65a4804efb739d1f5fe64c8f55dae758933471a6

pvmfw/src/entry.rs

diff --git a/pvmfw/src/entry.rs b/pvmfw/src/entry.rs
index a606462..99c67fb 100644
--- a/pvmfw/src/entry.rs
+++ b/pvmfw/src/entry.rs
@@ -18,7 +18,7 @@
 use crate::mmio_guard;
 use core::arch::asm;
 use core::slice;
-use log::{debug, LevelFilter};
+use log::{debug, error, LevelFilter};
 use vmbase::{console, logger, main, power::reboot};
 
 #[derive(Debug, Clone)]
@@ -77,6 +77,11 @@
     // This wrapper allows main() to be blissfully ignorant of platform details.
     crate::main(fdt, payload);
 
+    mmio_guard::unmap(console::BASE_ADDRESS).map_err(|e| {
+        error!("Failed to unshare the UART: {e}");
+        RebootReason::InternalError
+    })?;
+
     Ok(())
 }
 

pvmfw/src/mmio_guard.rs

diff --git a/pvmfw/src/mmio_guard.rs b/pvmfw/src/mmio_guard.rs
index 421f2c4..2206052 100644
--- a/pvmfw/src/mmio_guard.rs
+++ b/pvmfw/src/mmio_guard.rs
@@ -26,6 +26,8 @@
     InfoFailed(smccc::Error),
     /// Failed to MMIO_GUARD_MAP a page.
     MapFailed(smccc::Error),
+    /// Failed to MMIO_GUARD_UNMAP a page.
+    UnmapFailed(smccc::Error),
     /// The MMIO_GUARD granule used by the hypervisor is not supported.
     UnsupportedGranule(usize),
 }
@@ -38,6 +40,7 @@
             Self::EnrollFailed(e) => write!(f, "Failed to enroll into MMIO_GUARD: {e}"),
             Self::InfoFailed(e) => write!(f, "Failed to get the MMIO_GUARD granule: {e}"),
             Self::MapFailed(e) => write!(f, "Failed to MMIO_GUARD map: {e}"),
+            Self::UnmapFailed(e) => write!(f, "Failed to MMIO_GUARD unmap: {e}"),
             Self::UnsupportedGranule(g) => write!(f, "Unsupported MMIO_GUARD granule: {g}"),
         }
     }
@@ -56,6 +59,10 @@
     mmio_guard_map(helpers::page_4kb_of(addr) as u64).map_err(Error::MapFailed)
 }
 
+pub fn unmap(addr: usize) -> Result<()> {
+    mmio_guard_unmap(helpers::page_4kb_of(addr) as u64).map_err(Error::UnmapFailed)
+}
+
 fn mmio_guard_info() -> smccc::Result<u64> {
     const VENDOR_HYP_KVM_MMIO_GUARD_INFO_FUNC_ID: u32 = 0xc6000005;
     let args = [0u64; 17];
@@ -77,3 +84,11 @@
 
     smccc::checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID, args)
 }
+
+fn mmio_guard_unmap(ipa: u64) -> smccc::Result<()> {
+    const VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID: u32 = 0xc6000008;
+    let mut args = [0u64; 17];
+    args[0] = ipa;
+
+    smccc::checked_hvc64_expect_zero(VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID, args)
+}