This library may be used with the caches and MMU off, while the hypervisor has the caches enabled. So add explicit cache maintenance to deal with the potential incoherency.
Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel <[email protected]> --- .../XenConsoleSerialPortLib.c | 29 ++++++++++++++++++++++ .../XenConsoleSerialPortLib.inf | 1 + 2 files changed, 30 insertions(+) diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c index 467cb27a30c4..17d5a5a38d30 100644 --- a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c +++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c @@ -19,6 +19,7 @@ #include <Library/BaseLib.h> #include <Library/SerialPortLib.h> #include <Library/XenHypercallLib.h> +#include <Library/CacheMaintenanceLib.h> #include <IndustryStandard/Xen/io/console.h> #include <IndustryStandard/Xen/hvm/params.h> @@ -80,6 +81,13 @@ SerialPortWrite ( return 0; } + // + // We may be accessing DRAM directly, while the hypervisor has the caches + // enabled. This means we have to force a writeback to ensure that we have + // the latest data. + // + WriteBackDataCacheRange (mXenConsoleInterface, sizeof(*mXenConsoleInterface)); + Consumer = mXenConsoleInterface->out_cons; Producer = mXenConsoleInterface->out_prod; @@ -93,6 +101,13 @@ SerialPortWrite ( mXenConsoleInterface->out_prod = Producer; + // + // Ensure that the data cache is invalidated after we have written our data. + // This ensures that the hypervisor will have to fetch the value from DRAM, + // which may be where the data is if we are running with the MMU off. + // + InvalidateDataCacheRange (mXenConsoleInterface, sizeof(*mXenConsoleInterface)); + if (Sent > 0) { XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain); } @@ -124,6 +139,13 @@ SerialPortRead ( return 0; } + // + // We may be accessing DRAM directly, while the hypervisor has the caches + // enabled. This means we have to force a writeback to ensure that we have + // the latest data. + // + WriteBackDataCacheRange (mXenConsoleInterface, sizeof(*mXenConsoleInterface)); + Consumer = mXenConsoleInterface->in_cons; Producer = mXenConsoleInterface->in_prod; @@ -137,6 +159,13 @@ SerialPortRead ( mXenConsoleInterface->in_cons = Consumer; + // + // Ensure that the data cache is invalidated after we have written our data. + // This ensures that the hypervisor will have to fetch the value from DRAM, + // which may be where the data is if we are running with the MMU off. + // + InvalidateDataCacheRange (mXenConsoleInterface, sizeof(*mXenConsoleInterface)); + XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain); return Received; diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf index 8a7411558fa3..2fd1c654be78 100644 --- a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf +++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf @@ -29,6 +29,7 @@ [LibraryClasses] BaseLib XenHypercallLib + CacheMaintenanceLib [Packages] MdePkg/MdePkg.dec -- 1.8.3.2 ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ edk2-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/edk2-devel
