On 1/26/2024 10:58 PM, David Hildenbrand wrote:
On 25.01.24 04:22, Xiaoyao Li wrote:
By default (due to the recent UPM change), restricted memory attribute is
shared. Convert the memory region from shared to private at the memory
slot creation time.
add kvm region registering function to check the flag
and convert the region, and add memory listener to TDX guest code to set
the flag to the possible memory region.
Without this patch
- Secure-EPT violation on private area
- KVM_MEMORY_FAULT EXIT (kvm -> qemu)
- qemu converts the 4K page from shared to private
- Resume VCPU execution
- Secure-EPT violation again
- KVM resolves EPT Violation
This also prevents huge page because page conversion is done at 4K
granularity. Although it's possible to merge 4K private mapping into
2M large page, it slows guest boot.
With this patch
- After memory slot creation, convert the region from private to shared
- Secure-EPT violation on private area.
- KVM resolves EPT Violation
Originated-from: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
include/exec/memory.h | 1 +
target/i386/kvm/tdx.c | 20 ++++++++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 7229fcc0415f..f25959f6d30f 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -850,6 +850,7 @@ struct IOMMUMemoryRegion {
#define MEMORY_LISTENER_PRIORITY_MIN 0
#define MEMORY_LISTENER_PRIORITY_ACCEL 10
#define MEMORY_LISTENER_PRIORITY_DEV_BACKEND 10
+#define MEMORY_LISTENER_PRIORITY_ACCEL_HIGH 20
/**
* struct MemoryListener: callbacks structure for updates to the
physical memory map
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 7b250d80bc1d..f892551821ce 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -19,6 +19,7 @@
#include "standard-headers/asm-x86/kvm_para.h"
#include "sysemu/kvm.h"
#include "sysemu/sysemu.h"
+#include "exec/address-spaces.h"
#include "hw/i386/x86.h"
#include "kvm_i386.h"
@@ -621,6 +622,19 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
return 0;
}
+static void tdx_guest_region_add(MemoryListener *listener,
+ MemoryRegionSection *section)
+{
+ memory_region_set_default_private(section->mr);
+}
That looks fishy. Why is TDX to decide what happens to other memory
regions it doesn't own?
We should define that behavior when creating these memory region, and
TDX could sanity check that they have been setup properly.
Let me ask differently: For which memory region where we have
RAM_GUEST_MEMFD set would we *not* want to set private as default right
from the start?
All memory regions have RAM_GUEST_MEMFD set will benefit from being
private as default, for TDX guest.
I will update the implementation to set RAM_DEFAULT_PRIVATE flag when
guest_memfd is created successfully, like
diff --git a/system/physmem.c b/system/physmem.c
index fc59470191ef..60676689c807 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -1850,6 +1850,8 @@ static void ram_block_add(RAMBlock *new_block,
Error **errp)
qemu_mutex_unlock_ramlist();
return;
}
+
+ new_block->flags |= RAM_DEFAULT_PRIVATE;
}
then this patch can be dropped, and the calling of
memory_region_set_default_private(mr) of Patch 45 can be dropped too.
I think this is what you suggested, right?
